Consumer medicine information

Chemists' Own Favic for Cold Sores

Famciclovir

BRAND INFORMATION

Brand name

Chemists' Own Favic for Cold Sores

Active ingredient

Famciclovir

Schedule

S3

 

Consumer medicine information (CMI) leaflet

Please read this leaflet carefully before you start using Chemists' Own Favic for Cold Sores.

SUMMARY CMI

CHEMISTS' OWN FAVIC FOR COLD SORES

Consumer Medicine Information (CMI) summary

The full CMI on the next page has more details. If you are worried about using this medicine, speak to your doctor or pharmacist.

1. Why am I using CHEMISTS' OWN FAVIC FOR COLD SORES?

CHEMISTS' OWN FAVIC FOR COLD SORES contains the active ingredient famciclovir. It is an antiviral medicine that is used to treat recurrent outbreaks of cold sores in adults who have a normal immune system.

For more information, see Section 1. Why am I using CHEMISTS' OWN FAVIC FOR COLD SORES? in the full CMI.

2. What should I know before I use CHEMISTS' OWN FAVIC FOR COLD SORES?

Do not use if you have ever had an allergic reaction to CHEMISTS' OWN FAVIC FOR COLD SORES or any of the ingredients listed at the end of the CMI. Talk to your doctor if you have any other medical conditions, take any other medicines, or are pregnant or plan to become pregnant or are breastfeeding.

For more information, see Section 2. What should I know before I use CHEMISTS' OWN FAVIC FOR COLD SORES? in the full CMI.

3. What if I am taking other medicines?

Some medicines may interfere with CHEMISTS' OWN FAVIC FOR COLD SORES and affect how it works.

A list of these medicines is in Section 3. What if I am taking other medicines? in the full CMI.

4. How do I use CHEMISTS' OWN FAVIC FOR COLD SORES?

Your doctor will give you instruction on how to take CHEMISTS' OWN FAVIC FOR COLD SORES tablets.

More instructions can be found in Section 4. How do I use CHEMISTS' OWN FAVIC FOR COLD SORES? in the full CMI.

5. What should I know while using CHEMISTS' OWN FAVIC FOR COLD SORES?

Things you should do
  • Tell your doctor if you become pregnant, make sure you tell your doctor or pharmacist before taking any further doses of CHEMISTS' OWN FAVIC FOR COLD SORES.
  • Tell your doctor if you are about to be started on any new medicine.
  • Tell any other doctor or dentist you visit that you or your child are using CHEMISTS' OWN FAVIC FOR COLD SORES.
Things you should not do
  • Do not take less than the recommended dose of 3 tablets, unless advised by your pharmacist.
  • Do not use CHEMISTS' OWN FAVIC FOR COLD SORES to treat any other medical complaints unless your doctor tells you to.
  • Do not give CHEMISTS' OWN FAVIC FOR COLD SORES to anyone else, even if they have the same condition as you.
Driving or using machines
  • Be careful driving or operating machinery until you know how CHEMISTS' OWN FAVIC FOR COLD SORES affects you.
  • This medicine can cause dizziness, sleepiness or confusion in some people.
Drinking alcohol
  • Avoid drinking alcohol
Looking after your medicine
  • Store CHEMISTS' OWN FAVIC FOR COLD SORES tablets in original carton at below 25°C until ready for use.

For more information, see Section 5. What should I know while using CHEMISTS' OWN FAVIC FOR COLD SORES? in the full CMI.

6. Are there any side effects?

Side effects of this medicine may include headache; dizziness; abdominal pain or bloating; nausea; vomiting; diarrhoea; itching or an itchy rash (urticaria); abnormal liver function test results; extreme sleepiness; hallucinations; painful or swollen joints; aching muscles; yellowing of the skin or eyes; palpitations; a rash on other parts of your body; swelling below the surface of the skin; severe blistering of the skin; unexplained bruising; purple patches, itching, burning of the skin; seizures or fits; difficulty breathing or swallowing, wheezing or coughing.

For more information, including what to do if you have any side effects, see Section 6. Are there any side effects? in the full CMI.



FULL CMI

CHEMISTS' OWN FAVIC FOR COLD SORES Treatment of Cold Sores

Active ingredient(s): famciclovir

Consumer Medicine Information (CMI)

This leaflet provides important information about using CHEMISTS' OWN FAVIC FOR COLD SORES. You should also speak to your doctor or pharmacist if you would like further information or if you have any concerns or questions about using CHEMISTS' OWN FAVIC FOR COLD SORES.

Where to find information in this leaflet:

1. Why am I using CHEMISTS' OWN FAVIC FOR COLD SORES?
2. What should I know before I use CHEMISTS' OWN FAVIC FOR COLD SORES?
3. What if I am taking other medicines?
4. How do I use CHEMISTS' OWN FAVIC FOR COLD SORES?
5. What should I know while using CHEMISTS' OWN FAVIC FOR COLD SORES?
6. Are there any side effects?
7. Product details

1. Why am I using CHEMISTS' OWN FAVIC FOR COLD SORES?

CHEMISTS' OWN FAVIC FOR COLD SORES is an antiviral medicine that is used to treat recurrent outbreaks of cold sores in adults who have a normal immune system.

Cold sores are an infection caused by a virus called herpes simplex type 1 (HSV-1). The infection is most commonly acquired as a baby or child from contact with parents or relatives, often from kissing.

Cold sores usually begin on or around the lips, mouth, and nose as small red bumps that turn into fluid-filled blisters. Cold sores can be tender and painful. Many people who get cold sores know when one is coming by a tingling, burning, itchy or painful sensation or redness in the area. This can happen very rapidly.

After redness and swelling develop, blisters form. The blisters may weep or burst and this can be painful. Then a shallow ulcer and yellow crust form as the cold sore dries. The crust eventually falls off, exposing new pink-coloured skin. Generally, the sores heal without scarring. After the initial infection has healed, the virus becomes dormant in nerve cells.

Cold sores can be unpredictable. The virus can become active again in the body, even after many years, resulting in recurrent outbreaks.

Even after many years, some people may experience recurring cold sores due to viral reactivation.

Some common triggers to a cold sore may include:

  • sun exposure
  • stress
  • fatigue
  • menstrual periods
  • fever
  • illness
  • dry chapped lips
  • skin trauma
  • a cold.

CHEMISTS' OWN FAVIC FOR COLD SORES does not cure the viral infection, however it helps to relieve the symptoms and shorten the duration of an outbreak.

The best results are obtained if the medicine is started as soon as possible after the first symptoms are noticed. These include tingling, itching or burning, or the appearance of redness or swelling. This is when the virus is reproducing rapidly.

2. What should I know before I use CHEMISTS' OWN FAVIC FOR COLD SORES?

Warnings

Do not use CHEMISTS' OWN FAVIC FOR COLD SORES if you are allergic medical conditions:

  • Famciclovir, the active ingredient
  • Penciclovir, a related antiviral medicine
  • Any of the ingredients listed at the end of this leaflet.

Some of the symptoms of an allergic reaction may include shortness of breath, Skin rash, itching or hives, swelling of the face, lips, tongue or other parts of the body, wheezing or troubled breathing.

Do not use CHEMISTS' OWN FAVIC FOR COLD SORES if:

  • the packaging is torn or shows signs of tampering
  • the expiry date printed on the pack has passed.

Tell your doctor or pharmacist if you are allergic to any other medicines, foods, preservatives, or dyes.

Tell your doctor if you have or have had any of the following medical conditions:

  • problems with your immune system (which helps fight off infections)
  • kidney disease
  • liver disease.

Your doctor may want to take special care if you have any of these conditions.

During treatment, you may be at risk of developing certain side effects. It is important you understand these risks and how to monitor for them. See additional information under Section 6. Are there any side effects?

Pregnancy and breastfeeding

Check with your doctor if you are pregnant or intend to become pregnant.

Talk to your doctor if you are breastfeeding or intend to breastfeed.

CHEMISTS' OWN FAVIC FOR COLD SORES should not be used during pregnancy unless necessary. Your doctor will discuss with you the potential risks of taking CHEMISTS' OWN FAVIC FOR COLD SORES during pregnancy, and will also advise you if you should take CHEMISTS' OWN FAVIC FOR COLD SORES while breast-feeding, based on the benefits and risks of your personal situation.

Talk to your doctor or pharmacist if you are not sure whether you should start taking this medicine.

If you have not told them about any of the above, tell him/her before you start taking CHEMISTS' OWN FAVIC FOR COLD SORES.

All medicines have benefits and risks. Your doctor has weighed the risks of you taking CHEMISTS' OWN FAVIC FOR COLD SORES against the benefits they expect it will have for you.

There is no evidence that CHEMISTS' OWN FAVIC FOR COLD SORES is addictive.

CHEMISTS' OWN FAVIC FOR COLD SORES is not recommended for use in children or adolescents under 18 years of age.

3. What if I am taking other medicines?

Tell your doctor or pharmacist if you are taking any other medicines, including any medicines, vitamins or supplements that you buy without a prescription from your pharmacy, supermarket or health food shop.

Some medicines and CHEMISTS' OWN FAVIC FOR COLD SORES may interfere with each other. These include:

  • probenecid, a prescription medicine used to treat gout (a disease with painful, swollen joints caused by uric acid crystals) and to increase blood levels of penicillin-type antibiotics
  • raloxifene, a medicine used to treat osteoporosis (a disease which causes bones to become less dense, gradually making them weaker, more brittle and likely to break)
  • medicines that can affect your kidneys.

You may need to take different amounts of these medicines or you may need to take different medicines. Your doctor and pharmacist have more information.

Your doctor OR Pharmacist can tell you what to do if you are taking any of these medicines.

Your doctor and pharmacist have more information on medicines to be careful with or avoid while taking this medicine.

4. How do I use CHEMISTS' OWN FAVIC FOR COLD SORES?

The usual dose is three 500 mg tablets taken together as a single dose. Swallow the tablets whole with a full glass of water.

The tablets may be taken with or without food. It is not necessary to chew or crush the tablet.

Follow all directions given to you by your doctor or pharmacist carefully.

These directions may differ from the information contained in this leaflet.

If you do not understand the instructions on the box, ask the doctor or pharmacist for help.

When to take CHEMISTS' OWN FAVIC FOR COLD SORES

Take CHEMISTS' OWN FAVIC FOR COLD SORES tablets as soon as possible after the first symptoms of a cold sore appear.

Symptoms include tingling, itching or burning or the appearance of redness and swelling.

Do not take the tablets if a hard crust has already formed on the cold sore.

Keep the tablets for the next episode.

How long to take it for

A single dose of CHEMISTS' OWN FAVIC FOR COLD SORES is all that is necessary for treating each episode of cold sores. The dose may be repeated if cold sores recur. Each pack of CHEMISTS' OWN FAVIC FOR COLD SORES for cold sores contains enough medicine for one dose.

If you use too much (Overdose)

You should immediately:

  • phone the Poisons Information Centre
    (by calling 13 11 26) for advice, or
  • contact your doctor, or
  • go to the Emergency Department at your nearest hospital.

You should do this even if there are no signs of discomfort or poisoning.

You may need medical attention.

5. What should I know while using CHEMISTS' OWN FAVIC FOR COLD SORES?

Things you should do

If you become pregnant, make sure you tell your doctor or pharmacist before taking any further doses of CHEMISTS' OWN FAVIC FOR COLD SORES.

They can discuss with you the risks of taking it while you are pregnant.

Remind your doctor and pharmacist that you are taking CHEMISTS' OWN FAVIC FOR COLD SORES if you are about to be started on any new medicine.

Tell any other doctors, dentists and pharmacists who are treating you that you are taking CHEMISTS' OWN FAVIC FOR COLD SORES.

Things you should not do

Do not take less than the recommended dose of 3 tablets, unless advised by your pharmacist.

If you stop your tablets suddenly, your condition may worsen or you may have unwanted side effects.

Do not take CHEMISTS' OWN FAVIC FOR COLD SORES to treat any other conditions unless your doctor or pharmacist tells you to.

Do not give CHEMISTS' OWN FAVIC FOR COLD SORES to anyone else, even if they have the same condition as you.

Driving or using machines

Be careful driving or operating machinery until you know how CHEMISTS' OWN FAVIC FOR COLD SORES affects you.

This medicine can cause dizziness, sleepiness or confusion in some people.

Things that may help your condition

Cold sores are contagious and the virus can be passed on from person to person through close physical contact or saliva, even when blisters are not present. The risk is much higher when the cold sore is visible, as the virus can be shed, making it easy to infect other people.

Take the following precautions to avoid spreading the virus:

  • keep the areas affected by the virus as clean and dry as possible
  • avoid touching or scratching the sore area as you may spread the virus on your fingers
  • do not share any objects that have been in contact with a cold sore (e.g. drinking glasses, eating utensils, or towels)
  • avoid direct skin-to-skin contact of the area with other people (e.g. kissing) until the cold sore has healed.

Looking after your medicine

Keep your tablets in the blister pack, until it is time to take them.

If you take the medicine out of the pack it may not keep well.

Keep your tablets in a cool dry place where the temperature stays below 25°C.

Do not store CHEMISTS' OWN FAVIC FOR COLD SORES or any other medicines in a bathroom or near a sink.

Do not leave it in the car or on windowsills.

Heat and dampness can destroy some medicines.

Keep CHEMISTS' OWN FAVIC FOR COLD SORES where children cannot reach it.

A locked cupboard at least one-and-a-half metres above the ground is a good place to store medicines.

When to discard your medicine

If your doctor tells you to stop taking this medicine or the expiry date has passed, ask your pharmacist what to do with any medicine that is left over.

6. Are there any side effects?

Tell the doctor or pharmacist as soon as possible if you or your child do not feel well while you are taking CHEMISTS' OWN FAVIC FOR COLD SORES.

All medicines can have side effects. Sometimes they are serious, most of the time they are not. You may need medical attention if you get some of the side effects.

Do not be alarmed by the following lists of side effects.

You may not experience any of them.

Ask your doctor or pharmacist to answer any questions you may have.

Less serious side effects

Less Serious Side effectsWhat to do
  • headache
  • dizziness
  • nausea (feeling sick) or vomiting
  • diarrhoea
  • itching or an itchy rash (urticaria)
  • abnormal liver function test results.
Speak to your doctor or Pharmacist if you have any of these less side effects and they worry you.

These side effects are usually mild.

Serious side effects

Serious side effectsWhat to do
  • a rash on other parts of your body
  • extreme sleepiness or confusion, usually in older people
  • hallucinations (seeing or hearing things that are not really there)
  • painful or swollen joints
  • aching muscles or muscle tenderness or weakness that is not caused by exercise.
  • yellowing of the skin or eyes (signs of jaundice)
  • palpitations (signs of abnormal heart beat)
Speak to your doctor or Pharmacist as soon as possible if you have any of these side effects.
  • swelling below the surface of the skin (e.g. swelling around the face, eye, eyelid or throat)
  • unexplained bruising, reddish or purplish patches on the skin or bleeding more easily than usual as it may indicate that the number of platelets (a type of blood cell responsible for blood clotting) in your blood are reduced
  • severe blistering of the skin or mucous membranes of the lips, eyes, mouth, nasal passages or genitals (signs of a serious skin reaction)
  • purple patches, itching, burning of the skin (signs of inflamed blood vessels)
  • seizures or fits
  • difficulty breathing or swallowing, wheezing or coughing, light-headedness, changes in alertness, skin reddening, facial/throat swelling, blue discoloration of the lips, tongue or skin (signs of severe allergic reaction).
Call your doctor straight away or go straight to the Emergency Department at your nearest hospital if you notice any of these serious side effects.

These are serious side effects. You may need urgent medical attention or hospitalisation. These side effects are rare.

Tell your doctor or pharmacist if you notice anything else that may be making you feel unwell.

Other side effects not listed here may occur in some people.

Reporting side effects

After you have received medical advice for any side effects you experience, you can report side effects to the Therapeutic Goods Administration online at www.tga.gov.au/reporting-problems. By reporting side effects, you can help provide more information on the safety of this medicine.

Always make sure you speak to your doctor or pharmacist before you decide to stop taking any of your medicines.

7. Product details

This medicine is only available with a doctor's prescription.

What CHEMISTS' OWN FAVIC FOR COLD SORES 500 mg tablet contains

Active ingredient
(Main ingredient)		Famciclovir
Other ingredients
(Inactive ingredients)
  • microcrystalline cellulose
  • sodium starch glycollate
  • magnesium stearate
  • hyprolose
  • OPADRY II 85F18378 White (ARTG No 12135).

Tablets do not contain gluten, lactose, sucrose, tartrazine or any other azo dyes.

Do not take this medicine if you are allergic to any of these ingredients.

What CHEMISTS' OWN FAVIC FOR COLD SORES looks like

CHEMISTS' OWN FAVIC FOR COLD SORES are white to off-white, capsule-shaped tablets with ‘FC 500’ on one.

Each pack contains 3 tablets.

AUST R 212115

Who distributes CHEMISTS' OWN FAVIC FOR COLD SORES?

Arrotex Pharmaceuticals Pty Ltd
15 – 17 Chapel Street
Cremorne
Victoria 3121
www.arrotex.com.au

This leaflet was prepared in March 2025

Published by MIMS May 2025

BRAND INFORMATION

Brand name

Chemists' Own Favic for Cold Sores

Active ingredient

Famciclovir

Schedule

S3

 

1 Name of Medicine

Famciclovir.

2 Qualitative and Quantitative Composition

Chemists' Own Favic for Cold Sores tablets come in one strength of 500 mg of famciclovir.
For the full list of excipients, see Section 6.1 List of Excipients.

3 Pharmaceutical Form

Chemists' Own Favic for Cold Sores tablets are white to off-white, capsule-shaped tablet with 'FC 500' on one side and plain on the other side.

4 Clinical Particulars

4.1 Therapeutic Indications

Chemists' Own Favic for Cold Sores is indicated for the treatment of recurrent herpes labialis (cold sores) in immunocompetent adults aged 18 years and over.

4.2 Dose and Method of Administration

Administration.

Famciclovir can be taken without regard to meals (see Section 5.2 Pharmacokinetic Properties, Effect of food).

Dosage - adults 18 years and older.

The recommended dosage is 1500 mg as a single dose. Initiate therapy at the earliest sign or symptom of a cold sore (e.g. tingling, itching or burning). Treatment was initiated within 1 hour of symptom onset in the recurrent herpes labialis clinical study.

Renal impairment.

As reduced clearance of penciclovir is related to reduced renal function, as measured by creatinine clearance, patients who have, or are at risk of renal impairment should be referred to their medical practitioner for screening of renal impairment and any subsequent dosage adjustment if necessary. Therefore, use of Chemists' Own Favic for Colds Sores in patients with renal impairment should only be under medical advice. The following modifications in dosage are recommended:
Chemists' Own Favic for Cold Sores is only available as unscored tablets containing 500 mg of famciclovir.
As these recommendations are not based on repeated dose data, patients with impaired renal function should be closely monitored for adverse effects. There are insufficient data to recommend a dosage for patients with creatinine clearance less than 10 mL/min/1.73 m2.
Since 4 hour haemodialysis results in approximately 75% reduction in plasma concentrations of penciclovir, the full adjusted dose (for patients with severe renal impairment) of famciclovir should be administered immediately following dialysis.

Hepatic impairment.

Dosage modification is not required for patients with mild to moderate hepatic impairment.

4.3 Contraindications

Chemists' Own Favic for Cold Sores is contraindicated in patients:
with known hypersensitivity to famciclovir or any excipient in the formulation; or
who have shown hypersensitivity to penciclovir.
Chemists' Own Favic for Cold Sores is not recommended for use in:
Patients who are immunocompromised.
Children and adolescents under 18 years of age.

4.4 Special Warnings and Precautions for Use

Use in hepatic impairment.

Famciclovir has not been studied in patients with severe hepatic impairment. Conversion of famciclovir to the active metabolite penciclovir may be impaired in these patients resulting in lower penciclovir plasma concentrations, and thus possibly a decrease of efficacy of famciclovir (see Section 5.2 Pharmacokinetic Properties).

Use in renal impairment.

As reduced clearance of penciclovir is related to reduced renal function, as measured by creatinine clearance, patients who have, or are at risk of renal impairment should be referred to their medical practitioner for screening for renal impairment, and any subsequent dosage adjustments if necessary. Appropriate dosage adjustments for renally impaired patients are provided (see Section 4.2 Dose and Method of Administration). Therefore, use of Chemists' Own Favic for Cold Sores in patients with renal impairment should only be under medical advice.

Use in the elderly.

No special precautions are required for elderly patients with normal renal function and patients with mild or moderate hepatic impairment.

Paediatric use.

Safety and efficacy of famciclovir in the treatment of herpes labialis in children and adolescents under 18 years of age has not been established. Therefore, use of Chemists' Own Favic for Cold Sores in this age group is not recommended.

Effects on laboratory tests.

No data available.

4.5 Interactions with Other Medicines and Other Forms of Interactions

Effects of other medicinal products on famciclovir.

No clinically significant interactions have been identified with famciclovir or penciclovir.

Probenecid.

Concurrent use of probenicid may result in increased plasma concentrations of penciclovir (active metabolite of famciclovir, see Section 5.2 Pharmacokinetic Properties).

Other drugs that affect renal physiology.

Could affect plasma levels of penciclovir (the active metabolite of famciclovir, see Section 5.2 Pharmacokinetic Properties).
Evidence from preclinical studies has shown no potential for induction of cytochrome P450.

Zidovudine.

In a phase I study, no significant drug interactions were observed after co-administration of zidovudine and famciclovir.
The conversion of the interactive metabolite 6-deoxy penciclovir is catalysed by aldehyde oxidase. Interactions with other drugs metabolised by this enzyme and/or inhibiting this enzyme could potentially occur. Clinical interaction studies of famciclovir with cimetidine and promethazine, in vitro inhibitors of aldehyde oxidase, did not show relevant effects on the formation of penciclovir. However, raloxifene, the most potent aldehyde oxidase inhibitor observed in vitro, could affect the formation of penciclovir and thus the efficacy of famciclovir. When raloxifene is co-administered with famciclovir, the clinical efficacy should be monitored.

Effects of famciclovir on with medicinal products.

Although famciclovir is only a weak inhibitor of aldehyde oxidase in vitro, interactions with drugs metabolised by aldehyde oxidase could potentially occur. Evidence from preclinical studies has shown no potential for induction of cytochrome P450 enzymes of inhibition of CYP3A4.

4.6 Fertility, Pregnancy and Lactation

Effects on fertility.

Testicular toxicity was observed in rats, mice and dogs following repeated administration of famciclovir or penciclovir. Testicular changes included atrophy of seminiferous tubules, reduction in sperm count and/or increased incidence of sperm with abnormal morphology or reduced motility. The degree of testicular toxicity was related to dose and duration of exposure and tended to reverse after the cessation of dosing. In male rats, decreased fertility was observed after 10 weeks dosing at 500 mg/kg/day, or approximately 3 to 20 times the human systemic exposure (AUC). Testicular toxicity was also seen in mice and dogs following chronic administration at exposures to penciclovir ranging from 2 to 14 times the human systemic exposure (AUC). However, there were no clinically significant effects on sperm count, morphology and motility in male patients receiving 250 mg famciclovir b.i.d. for 18 weeks. Famciclovir had no effect on fertility in female rats at doses of up to 1000 mg/kg/day, approximately 4 to 27 times the human systemic exposure (AUC).
(Category B1)
Famciclovir was tested for effects on embryo-foetal development in rats and rabbits at oral doses up to 1000 mg/kg/day (approximately 4 to 27 times and 2 to 12 times the human systemic exposure to penciclovir in rats and rabbits, respectively [AUC]), and intravenous doses of 360 mg/kg/day in rats (1.9 to 12 times the human dose based on body surface area [BSA] comparisons) or 120 mg/kg/day in rabbits (1.2 to 7.1 times the human dose [BSA]). No adverse effects were observed on embryo-foetal development. Similarly, no adverse effects were observed following intravenous administration of penciclovir to rats (80 mg/kg/day, 0.4 to 2.6 times the human dose [BSA]) or rabbits (60 mg/kg/day, 0.6 to 3.6 times the human dose [BSA]). Although animal studies have not shown any embryotoxic or teratogenic effects with famciclovir or penciclovir, the safety of famciclovir in human pregnancy has not been established. Chemists' Own Favic for Cold Sores should therefore not be used during pregnancy unless the potential benefits are considered to outweigh the potential risks associated with treatment.
 Chemists' Own Favic for Cold Sores should not be used by nursing mothers unless the potential benefits are considered to outweigh the potential risks associated with treatment. Following oral administration of famciclovir to lactating rats, penciclovir was excreted in milk at concentrations higher than those seen in plasma. There is no information on excretion in human milk.

4.7 Effects on Ability to Drive and Use Machines

Patients who experience dizziness, somnolence, confusion or other central nervous system disturbances while taking famciclovir should refrain from driving or operating machinery.

4.8 Adverse Effects (Undesirable Effects)

Famciclovir has been well tolerated in human studies. Headache, fatigue and nausea have been reported in clinical trials. These were generally mild or moderate and occurred at a similar incidence in patients receiving placebo treatment. Confusion, predominantly in the elderly, has been reported rarely.
The following adverse events occurred during the clinical trial in recurrent herpes labialis (see Table 2):

Post-marketing data.

In addition to the adverse events reported in the clinical trials, the following events have been reported in post marketing surveillance. They are ranked under heading of frequency, according to the following convention: very common (greater than or equal to 1/10); common (greater than or equal to 1/100, < 1/10); uncommon (greater than or equal to 1/1000, < 1/100); rare (greater than or equal to 10,000, < 1/1000); very rare (< 1/10,000), including isolated reports.
Adverse events reported by patients receiving famciclovir during post-marketing:

Blood and lymphatic system disorders.

Very rare: Thrombocytopenia.

Psychiatric disorders.

Uncommon: Confusion (predominantly in the elderly).
Rare: Hallucinations.

Nervous system disorders.

Very common: Headache.
Common: Dizziness.
Uncommon: Somnolence (predominantly in the elderly).
Not known: Seizure.

Cardiac disorders.

Rare: palpitations.

Gastrointestinal disorders.

Common: Nausea, vomiting, abdominal pain, diarrhoea.

Hepatobiliary disorders.

Common: abnormal liver function tests.
Rare: jaundice cholestatic.

Immune system disorder.

Not known: anaphylactic shock, anaphylactic reaction.

Skin and subcutaneous tissue disorders.

Common: Rash, pruritus.
Uncommon: angioedema (e.g. face oedema, eyelid oedema, periobital oedema, pharyngeal oedema), urticaria.
Very rare: serious skin reactions (e.g. erythema multiforme, Stevens-Johnson syndrome and toxic epidermal necrolysis).
Not known: hypersensitivity vasculitis.

Musculoskeletal disorders.

Very rare: arthralgia, myalgia.

Reporting suspected adverse effects.

Reporting suspected adverse reactions after registration of the medicinal product is important. It allows continued monitoring of the benefit-risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions at www.tga.gov.au/reporting-problems.

4.9 Overdose

Symptomatic and supportive therapy should be given as appropriate. Acute renal failure has been reported rarely in patients with underlying renal disease. The famciclovir dosage in these patients had not been appropriately reduced for the level of renal function.
Penciclovir is dialysable; plasma concentrations are reduced by approximately 75% following 4 hour haemodialysis.
For information on the management of overdose, contact the Poisons Information Centre on 13 11 26 (Australia).

5 Pharmacological Properties

5.1 Pharmacodynamic Properties

Mechanism of action.

Famciclovir is the oral form of penciclovir. Famciclovir is rapidly converted in vivo into penciclovir, which has demonstrable in vitro activity against herpes simplex viruses (HSV types 1 and 2) and varicella zoster virus (VZV). The antiviral effect of orally administered famciclovir has been demonstrated in several animal models: this effect is due to in vivo conversion to penciclovir.
Penciclovir targets virus-infected cells where it is rapidly converted into penciclovir-triphosphate (mediated via virus-induced thymidine kinase). The triphosphate inhibits viral DNA polymerase by competition with deoxyguanosine triphosphate and is incorporated into the extending DNA chain, preventing significant chain elongation. Consequently, viral DNA synthesis and, therefore, viral replication are inhibited.
This triphosphate persists in infected cells in excess of 12 hours. The long intracellular half-life of penciclovir triphosphate ensures prolonged antiviral activity, as demonstrated in cell cultures with HSV-1 and HSV-2 and in animal studies.
Penciclovir is only readily phosphorylated in virus-infected cells. In uninfected cells treated with penciclovir, concentrations of penciclovir-triphosphate are only barely detectable. Accordingly, uninfected cells are unlikely to be affected by therapeutic concentrations of penciclovir.
The most common form of resistance encountered with aciclovir among HSV strains is a deficiency in the production of the thymidine kinase (TK) enzyme. Such TK deficient strains would be expected to be cross-resistant to both penciclovir and aciclovir. However, penciclovir has been shown to be active against a clinically isolated acyclovir-resistant herpes simplex type 1 strain with an altered DNA polymerase.
The results from penciclovir and famciclovir patient studies, including studies of up to four months' treatment with famciclovir, showed that no resistance occurred as a result of treatment with either famciclovir or penciclovir. Penciclovir-resistant isolates were found at the start of treatment or in the placebo groups in 0.25% of the 1976 total isolates from HSV and VZV (5/1976), and in 0.19% of the 533 virus isolates from immunocompromised patients (1/533).

Clinical trials.

In one large placebo-controlled trial, 701 immunocompetent adults with recurrent herpes labialis were treated with famciclovir 1500 mg once (n=227), famciclovir 750 mg b.i.d. (n=220) or placebo (n=254) for 1 day. As well, patients also had to be in good general health, aged at least 18 years, have normal renal and hepatic function, had prior pregnancy tests if they were females of reproductive age, and have experienced 3 or more episodes of cold sores in the preceding 12 months. Patients were required to have a history of prodromal symptoms preceding at least 50% of the recurrent episodes, and at least 50% of these episodes had to have progressed to the vesicular lesion stage. Women of childbearing potential had to agree to use reliable birth control measures during the study. Pregnant or breast-feeding women were excluded. Patients were excluded if they had received an investigational drug in the 4 weeks prior to the study, had been previously vaccinated against herpes, or were using a topical immunosuppressive agent on or near the face or a systemic immunosuppressive agent within 1 month of screening. Patients were also excluded if they were immunosuppressed due to underlying disease or concomitant treatment had a recent history of drug or alcohol abuse, were suffering from inflammatory skin diseases (e.g. eczema or dermatitis) that would interfere with the assessment of lesions, or were allergic or hypersensitive to products containing aciclovir, penciclovir, famciclovir or other nucleoside analogs.
Patients were instructed to take the first dose of study medication within 1 hour of symptom onset. However, some patients commenced treatment after 1 hour of onset of symptoms. Both famciclovir regimens significantly reduced time to healing of primary vesicular herpes labialis lesions (the primary efficacy variable) in the modified ITT population compared with placebo. The median time to healing in famciclovir 1500 mg single-dose treated patients was 4.4 days compared to 4.0 days in famciclovir 750 mg bid and 6.2 days in placebo-treated patients. This translates to treatment effects of 1.8 (CI 95% 0.9, 2.7) and 2.2 (CI 95% 1.3, 3.1) days, respectively. A single 1500 mg dose of famciclovir reduced the time to resolution of pain and tenderness (median time 1.7 days versus 2.9 days) compared with placebo and was marginally more effective than famciclovir 750 mg b.i.d. (median time 2.1 days).

5.2 Pharmacokinetic Properties

Absorption.

Following oral administration, famciclovir is rapidly and extensively absorbed and converted to the antivirally active compound penciclovir. Bioavailability of penciclovir after oral famciclovir is 77%. Mean peak plasma concentrations of penciclovir following a 125 mg, 250 mg, 500 mg, 750 mg and 1000 mg oral dose of famciclovir were 0.8 microgram/mL, 1.6 microgram/mL, 3.3 microgram/mL, 5.1 microgram/mL, and 6.6 microgram/mL respectively, and occurred at a median time of 45 mins post dose. There are no data on the pharmacokinetics of the 1500 mg single dose.

Distribution.

Plasma concentration-time curves of penciclovir are similar following single and repeat (b.i.d. and t.i.d.) dosing and there is no accumulation of penciclovir on repeated dosing. Penciclovir and its 6-deoxy precursor are poorly (< 20%) bound to plasma proteins.

Metabolism.

Famciclovir is the oral prodrug of penciclovir.

Excretion.

Famciclovir is eliminated principally as penciclovir and its 6-deoxy precursor, which are excreted in urine. No unchanged famciclovir has been detected in urine. Tubular secretion and glomerular filtration contribute to renal elimination of the compound. The terminal plasma half-life of penciclovir after both single and repeat dosing with famciclovir is approximately 2.0 hours. There is no accumulation of penciclovir on repeated dosing with famciclovir.

Effect of food.

Penciclovir Cmax was decreased by approximately 50% and Tmax was delayed by 1.5 h when a capsule formulation of famciclovir was administered 30 minutes after food. When famciclovir tablets were administered 30 minutes after food, penciclovir Cmax was reduced by approximately 20% and Tmax was delayed by 0.75 h. The systemic availability (AUC) of penciclovir following either preparation was unaffected. The clinical consequences of these effects on plasma concentration are unknown.

Characteristics in special populations.

Renal impairment.

Plasma clearance, renal clearance and plasma elimination rate constant decreased linearly with reductions in renal function. A dosage interval adjustment is recommended for patients with renal insufficiency (see Section 4.2 Dose and Method of Administration).

Hepatic impairment.

Well-compensated chronic liver disease (chronic hepatitis [n=6], chronic ethanol abuse [n=8] or biliary cirrhosis [n=1]) has no effect on the extent of availability (AUC) of penciclovir following a single dose of 500 mg famciclovir. No dose adjustment is recommended for patients with well-compensated hepatic impairment (see Section 4.2 Dose and Method of Administration, Hepatic impairment; Section 4.4 Special Warnings and Precautions for Use). However, there was a 43% decrease in penciclovir mean maximum plasma concentration and the time to maximum plasma concentration was increased by a median of 0.75 h in patients with hepatic insufficiency compared to normal volunteers. The pharmacokinetics have not been evaluated in patients with severe uncompensated hepatic impairment.

Elderly patients.

Based on cross-study comparisons of single dose studies, the mean penciclovir AUC was approximately 30% larger, half-life 23% longer and penciclovir body weight adjusted renal clearance reduced by 19% in healthy elderly male volunteers (n=18, aged 65 to 79 years) compared to younger volunteers. Some of this difference may be due to differences in renal function between the two groups. No dosage adjustment based on age is recommended unless renal function is impaired (see Section 4.2 Dose and Method of Administration).

Race.

A retrospective evaluation was performed to compare the pharmacokinetic parameters obtained in black and Caucasian subjects after single and repeat once daily, twice daily, or three times daily administration of famciclovir 500 mg. Data from a study in healthy volunteers (single dose), a study in subjects with varying degrees of renal impairment (single and repeat dose) and a study in subjects with hepatic impairment (single dose) did not indicate any relevant differences in the pharmacokinetics of penciclovir between black and Caucasian subjects.

5.3 Preclinical Safety Data

Data presented below include reference to area under the plasma concentration curve (24 hour AUC) for penciclovir in humans following the lowest and highest recommended doses for famciclovir (i.e. penciclovir AUC of 4.5 microgram.h/mL at 125 mg b.i.d. for acute recurrent genital herpes, and a penciclovir AUC of 27 microgram.h/mL at 500 mg t.i.d. for herpes infections in immunocompromised patients). This is based on the assumption that the pharmacokinetics in immunocompetent subjects are similar to the pharmacokinetics in immunocompromised subjects, as shown in the study on HIV patients (see Section 5.2 Pharmacokinetic Properties). If the higher values of AUC obtained in the renal transplant patients were used as a basis for comparison, the multiples specified here would be decreased.
Exposures in animal studies are expressed as multiples of human exposures at the highest and lowest dosing schedules based on penciclovir AUC or body surface area.

Genotoxicity.

Famciclovir and penciclovir (the active metabolite of famciclovir) were tested for genotoxic potential in a series of in vitro and in vivo assays. Famciclovir showed no genotoxic potential in a series of assays for gene mutations, chromosomal damage and DNA damage. Penciclovir was positive in the L5178Y mouse lymphoma assay for gene mutations/chromosomal damage, caused chromosomal aberrations in human lymphocytes in vitro and was positive in a mouse micronucleus assay in vivo when administered IV at doses toxic to bone marrow.

Carcinogenicity.

The carcinogenic potential of famciclovir was evaluated in 2 year dietary studies in rats and mice. A significant increase in the incidence of mammary adenocarcinoma was seen in female rats receiving 600 mg/kg/day. No increases in tumour incidences were reported for male rats treated at doses of up to 240 mg/kg/day or in mice of either sex at doses of up to 600 mg/kg/day. At the no effect levels of 240 and 200 mg/kg/day in male and female rats, the daily exposures to penciclovir based on AUC were about 40 and 29 microgram.h/mL respectively, or approximately 1 to 8 times the human systemic exposures at 500 mg t.i.d or 125 mg b.i.d. Systemic exposures at the no effect dose in male and female mice were 65 and 46 microgram.h/mL respectively, or approximately 2 to 12 times the human systemic exposure (AUC).

6 Pharmaceutical Particulars

6.1 List of Excipients

Chemists' Own Favic for Cold Sores tablets contain the following excipients: sodium starch glycollate, microcrystalline cellulose, hyprolose, magnesium stearate, and Opadry II complete film-coating system 85F18378 White.
The tablets are gluten free.

6.2 Incompatibilities

Incompatibilities were either not assessed or not identified as part of the registration of this medicine.

6.3 Shelf Life

In Australia, information on the shelf life can be found on the public summary of the Australian Register of Therapeutic Goods (ARTG). The expiry date can be found on the packaging.

6.4 Special Precautions for Storage

Store below 25°C.

6.5 Nature and Contents of Container

Chemists' Own Favic for Cold Sores tablets are available in blister packs (PVC/PVDC/Al) of 3 tablets.

6.6 Special Precautions for Disposal

In Australia, any unused medicine or waste material should be disposed of by taking to your local pharmacy.

6.7 Physicochemical Properties

Famciclovir is a white or off-white crystalline powder. Soluble in water (25°): > 25% w/v initially; rapidly precipitates as sparingly soluble monohydrate (2-3% w/v). Freely soluble in acetone, methanol; sparingly soluble in ethanol, isopropanol.

Chemical structure.

The chemical name for famciclovir is 2-[2-(2-Amino-9H- purin-9-yl)ethyl]-1,3-propanediol diacetate. Its structural formula is:
C14H19N5O4. Molecular weight: 321.34.

CAS number.

104227-87-4.

7 Medicine Schedule (Poisons Standard)

Schedule 3 - Pharmacist Only Medicine.

Summary Table of Changes