Consumer medicine information

ARX-Nitrofurantoin

Nitrofurantoin

BRAND INFORMATION

Brand name

ARX-Nitrofurantoin

Active ingredient

Nitrofurantoin

Schedule

What is in this leaflet

Please read this leaflet carefully before you start taking ARX-NITROFURANTOIN.

This leaflet answers some common questions about ARX-NITROFURANTOIN. It does not contain all the available information and it does not take the place of talking to your doctor or pharmacist.

All medicines have risks and benefits. Your doctor has weighed the risks of you taking this medicine against the expected benefits it will have for you.

Take ARX-NITROFURANTOIN as instructed and follow the advice given in this leaflet.

If you have any concerns about taking this medicine, ask your doctor or pharmacist.

Keep this leaflet with the medicine. You may need to read it again.

What ARX-NITROFURANTOIN is used for

ARX-NITROFURANTOIN is used to treat infections of the urinary system caused by bacteria, for example, bladder infections.

ARX-NITROFURANTOIN is an antibiotic which belongs to a group of medicines called nitrofurans. It works by killing or stopping the growth of the bacteria and other organisms causing these infections.

Your doctor may have prescribed ARX-NITROFURANTOIN for another reason. Ask your doctor if you have any questions about why ARX-NITROFURANTOIN has been prescribed for you.

These medicines are only available with a doctor's prescription.

Before you take ARX-NITROFURANTOIN

When you must not take it

Do not take ARX-NITROFURANTOIN if:

You have an allergy to ARX-NITROFURANTOIN or any other nitrofuran, or to any of the ingredients listed at the end of this leaflet. Symptoms of an allergic reaction include skin rash, itching, difficulty with breathing, fever and chills.
you have severe kidney problems
you are pregnant and close to giving birth.

Infants under one month of age should not be given ARX-NITROFURANTOIN.

Do not take ARX-NITROFURANTOIN if the packaging is torn or shows signs of tampering.

Do not take it after the expiry date (EXP) printed on the pack.

Before you start taking it

You must tell your doctor if:

You are pregnant or intend to become pregnant. Your doctor will discuss the risks and benefits of taking ARX-NITROFURANTOIN during pregnancy
You are breastfeeding or intend to breastfeed. Your doctor will discuss the risks and benefits of taking ARX-NITROFURANTOIN while breastfeeding.
you have or have had any other health problems including:

kidney problems
if you lack an enzyme in red blood cells (G-6-PD deficiency) which occurs in a very small number of people of African descent, people of Mediterranean and near Eastern origin.
anaemia (a blood disorder), diabetes, or vitamin B deficiency.

When taking ARX-NITROFURANTOIN your urine may turn brown. This is temporary and not associated with any serious effects.

ARX-NITROFURANTOIN may interfere with the normal production of sperm cells. This is reversible. If this causes you any concerns, please speak to your doctor.

If you have not told your doctor or pharmacist about any of the above, tell them before you start to take ARX-NITROFURANTOIN.

Taking other medicines

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

There may be interference between ARX-NITROFURANTOIN and some other medicines including:

phenobarbitone, a medicine used to treat epilepsy
medicines used to treat gout, such as probenecid and sulfinpyrazone
antacids, medicines used to treat heartburn, indigestion or reflux
agents used to make the urine more acidic, such as ammonium chloride tablets
agents used to make the urine more alkaline, such as sodium bicarbonate.

These medicines may be affected by ARX-NITROFURANTOIN or may affect how well they work.

You may need different amounts of your medicine or you may need to take different medicines. Your doctor or pharmacist has more information on medicines to be careful with or avoid while taking ARX-NITROFURANTOIN.

How to take ARX-NITROFURANTOIN

Your doctor or pharmacist will tell you how to take your medicine. Follow all directions given to you by your doctor or pharmacist carefully. The directions given to you by your doctor or pharmacist on how to take ARX-NITROFURANTOIN may differ from the information contained in this leaflet. You may be given a different dosage depending on your condition or how you react to the medicine. If you do not understand the instructions on the label, ask your doctor or pharmacist for help.

How much to take

Adults

If you already have an infection: The usual dose is 1 capsule (either the 50 mg or 100 mg strength) four times daily.

To prevent an infection:

The usual dose is 1 capsule (either the 50 mg or 100 mg strength) taken at night.

Children

The dose for children will depend on their body weight. The usual dose is 1.25 to 1.75 mg/kg of body weight given four times a day. Your doctor will calculate the proper dose taking into account the age and weight of the child and how severe the infection is.

When to take it

ARX-NITROFURANTOIN should be swallowed with or immediately after food or with a glass of milk. If taken on an empty stomach it may cause stomach upset.

How long to take it

Continue taking ARX-NITROFURANTOIN until you finish the given carton pack or until your doctor recommends.

Do not stop taking your medicine earlier than this, even if you are feeling better.

Check with your doctor if you are not sure how long you should be taking the medicine.

If you forget to take it

If it is almost time for your next dose, skip the dose you missed and take your next dose when you are meant to. Otherwise, take it as soon as you remember, then go back to taking your medicine as you would normally.

Do not try to make up for missed doses by taking more than one dose at a time.

If you take too much (overdose)

Immediately telephone your doctor, or the Poisons Information Centre (telephone 13 11 26), or go to the Accident and Emergency at your nearest hospital, if you think you or anyone else may have taken too much ARX-NITROFURANTOIN. Do this even if there are no signs of discomfort or poisoning. You may need urgent medical attention. Keep telephone numbers for these services handy. Have the medicine or this leaflet available to give details if needed.

While you are using ARX-NITROFURANTOIN

Things you must do

If the symptoms of your infection do not improve, or if they become worse, tell your doctor
If you become pregnant while you are taking ARX-NITROFURANTOIN, tell your doctor
If you are about to start taking any new medicines, tell your doctor and pharmacist that you are taking ARX-NITROFURANTOIN
If you have to have any urine or blood tests, tell your doctor you are taking ARX-NITROFURANTOIN. This medicine may affect the results of some laboratory tests
Tell all doctors, dentists and pharmacists who are treating you that you are taking ARX-NITROFURANTOIN.

Things you must not do

Do not stop taking your medicine before you finish the given carton pack or as advised by your doctor, even if you are feeling better.

If you do not complete the full course prescribed by your doctor, all of the bacteria causing your infection may not be killed. These bacteria may continue to grow and multiply so that your infection may not clear completely or may return.

Do not take antacid preparations at the same time as ARX-NITROFURANTOIN. These preparations may affect how well ARX-NITROFURANTOIN works.

Do not give ARX-NITROFURANTOIN to anyone else, even if they have the same condition as you.

Do not use ARX-NITROFURANTOIN to treat any other medical complaints unless your doctor tells you to.

Side effects

Check with your doctor as soon as possible if you have any problems while taking ARX-NITROFURANTOIN, even if you do not think the problems are connected with the medicine or are not listed in this leaflet.

Like many medicines, ARX-NITROFURANTOIN may cause side effects. If they occur, they are likely to be minor and temporary. However, some may be serious and need medical attention.

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

Tell your doctor if you notice any of the following and they worry you:

nausea and vomiting
diarrhoea
headache and dizziness
drowsiness and altered mood
feeling weak.

Tell your doctor immediately if you notice any of the following:

swelling of the face, lips, mouth, throat or neck which may cause difficulty with swallowing or breathing
diarrhoea (which may occur up to several weeks after finishing the course)
numbness or tingling in any area of the body
confusion, having hallucinations or illusions
hepatitis, an inflammation of the liver which can result in yellowing of the skin and eyes, lower back pain, dark urine, tiredness and a general feeling of being unwell
fever and chills
chest pain, difficulty with breathing and cough
skin rash and itchiness
asthma attack
sore throat or gums and a continual feeling of tiredness.

Other side effects not listed above may also occur in some patients.

Do not be alarmed by this list of possible side effects. You may not experience any of them.

After taking ARX-NITROFURANTOIN

Storage

Keep the medicine in the blister pack until it is time to take it. If you take the capsules out of the blister, the medicine may not keep well.

Keep the medicine in a cool dry place. ARX-NITROFURANTOIN must be stored where it stays below 25°C. Do not store ARX-NITROFURANTOIN, or any other medicine in a bathroom or near a sink. Do not leave the medicine in the car or on window sills. Heat and dampness can destroy some medicines.

Keep your ARX-NITROFURANTOIN 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.

Disposal

If your doctor tells you to stop taking ARX-NITROFURANTOIN, or the medicine has passed its expiry date, ask your pharmacist what to do with any left over.

Product Description

What it looks like

ARX-NITROFURANTOIN is available as 50 mg and 100 mg capsules. These are supplied in Blister Pack of 3 X 10 Capsules (30 capsules) per carton.

The 50 mg capsules are Size '3' opaque yellow cap and opaque white body hard gelatin capsule, imprinted with “EM28” with 360 degree thin band, in black ink on cap filled with yellow powder.
Registration number:
AUST R 373271

The 100 mg capsules are Size '2' opaque yellow cap and opaque yellow body hard gelatin capsule, imprinted with “EM29” with 360 degree thin band, in black ink on cap filled with yellow powder.
Registration number:
AUST R 373270

Ingredients

ARX-NITROFURANTOIN capsules contain either 50 mg or 100 mg of nitrofurantoin (Macrocrystals) as the active ingredient. Other ingredients include Lactose Monohydrate, Pregelatinized Starch and purified talc.

The capsule shells contain gelatin, titanium dioxide, quinoline yellow, Iron oxide Yellow, sodium lauryl sulfate and Black Ink TEK SW 9008

Supplier

ARX-NITROFURANTOIN is supplied in Australia by:

Luminarie Pty Ltd

Distributed by:

Arrotex Pharmaceuticals
15–17 Chapel Street
Cremorne VIC 3121

This leaflet was prepared in November 2022.

Published by MIMS January 2023

BRAND INFORMATION

Brand name

ARX-Nitrofurantoin

Active ingredient

Nitrofurantoin

Schedule

Notes

Distributed by Arrotex Pharmaceuticals Pty Ltd

1 Name of Medicine

ARX-Nitrofurantoin capsules 50 mg and 100 mg (nitrofurantoin macrocrystals).

2 Qualitative and Quantitative Composition

Each 50 mg and 100 mg of ARX-Nitrofurantoin capsule contains 50 mg and 100 mg of nitrofurantoin (macrocrystals) respectively.

Excipient with known effect.

"Lactose monohydrate".
For the full list of excipients, see Section 6.1 List of Excipients.

3 Pharmaceutical Form

Nitrofurantoin capsules (macrocrystals) 50 mg.

Size '3' opaque yellow cap and opaque white body hard gelatin capsule, imprinted with "EM28" with 360 degree thin band, in black ink on cap filled with yellow powder.

Nitrofurantoin capsules (macrocrystals) 100 mg.

Size '2' opaque yellow cap and opaque yellow body hard gelatin capsule, imprinted with "EM29" with 360 degree thin band, in black ink on cap filled with yellow powder.

4 Clinical Particulars

4.1 Therapeutic Indications

Treatment of urinary tract infections such as cystitis and pyelitis when due to susceptible pathogens. Nitrofurantoin does not reach effective levels in plasma and consequently is not indicated for cortical or perinephric abscesses and in cases of prostatitis.

4.2 Dose and Method of Administration

To be taken with food or milk.

Adults.

50-100 mg four times a day. Do not exceed 400 mg daily.
Prophylactic therapy: 50 mg or 100 mg night.

Children.

Should be calculated on the basis of 5-7 mg/kg body weight per 24 hours to be given in divided doses four times a day.
ARX-Nitrofurantoin should not be administered to infants under one month of age.
Therapy should be continued for at least one week and for at least 3 days after sterility of the urine is obtained. Continued infection indicates the need for re-evaluation. If the drug is to be used for prophylactic or for long-term suppressive therapy, consideration should be given to finding the lowest effective dose.

4.3 Contraindications

Anuria and oliguria or extensive impairment of renal function (creatinine clearance under 60 mL/min or clinically significant elevated serum creatinine); hypersensitivity to furan derivatives; nitrofurantoin should not be administered to pregnant women during labour and delivery, or when the onset of labour is imminent or to infants under one month of age because of the possibility of producing a haemolytic anaemia due to immature enzyme systems (glutathione instability) in the early neonatal period.

4.4 Special Warnings and Precautions for Use

Peripheral neuropathy.

Peripheral neuropathy (including optic neuritis), which may become severe or irreversible, has occurred. Fatalities have been reported. Conditions such as renal impairment (creatinine clearance under 60 mL/min or clinically significant elevated serum creatinine), anaemia, diabetes mellitus, electrolyte imbalance, vitamin B deficiency, and debilitating disease may enhance the occurrence of peripheral neuropathy. Patients receiving long-term therapy should be monitored periodically for changes in renal function. If numbness or tingling occurs in any area, administration of the drug should be discontinued (see Section 4.8 Adverse Effects (Undesirable Effects), Neurological).

Use in hepatic impairment.

Hepatic reactions, including hepatitis, cholestatic jaundice, chronic active hepatitis and hepatic necrosis occur rarely. Fatalities have been reported. The onset of chronic active hepatitis may be insidious, and patients should be monitored periodically for changes in liver function. If hepatitis occurs, the drug should be withdrawn immediately and appropriate measures should be taken (see Section 4.8 Adverse Effects (Undesirable Effects), Hepatic).

Use in renal impairment or acidosis.

In the presence of impairment of renal function or acidosis, administer nitrofurantoin with caution. If employed under such circumstances the blood pH, CO₂- content or combining power and urea nitrogen or non-protein nitrogen should be followed closely. This is particularly important if treatment is continued beyond fourteen days.

Pulmonary reactions.

Acute, subacute or chronic pulmonary reactions have been observed in patients treated with nitrofurantoin. These reactions can be life threatening; therefore, if they occur treatment should be stopped immediately. Chronic pulmonary reactions (diffuse interstitial pneumonitis or pulmonary fibrosis, or both) can develop insidiously. These reactions occur rarely and generally in patients receiving therapy for six months or longer. Close monitoring of the pulmonary condition of patients receiving long-term therapy is warranted and requires that the benefits of therapy be weighed against potential risks (see Section 4.8 Adverse Effects (Undesirable Effects), Pulmonary hypersensitivity).

Haemolytic anaemia.

Haemolytic anaemia of the primaquine-sensitivity type has been induced by nitrofurantoin. The haemolysis appears to be linked to a glucose-6-phosphate dehydrogenase deficiency in the affected patients' red blood cells. This deficiency is found in 10% of African descent individuals and in a small percentage of ethnic groups of Mediterranean and Near Eastern origin. G6PD deficiency has also been reported occasionally amongst Caucasian groups. Any sign of haemolysis is an indication to discontinue the drug. Haemolysis ceases when the drug is withdrawn.

Colitis.

Antibiotic associated Pseudomembranous colitis has been reported with many antibacterials including sporadic reports with nitrofurantoin. A toxin produced with Clostridium difficile appears to be the primary cause. The severity of the colitis may range from mild to life threatening. It is important to consider this diagnosis in patients who develop diarrhoea or colitis in association with antibiotic use (this may occur up to several weeks after cessation of antibiotic therapy). Mild cases usually respond to drug discontinuation alone. However, in moderate to severe cases appropriate therapy with a suitable oral antibacterial agent effective against Clostridium difficile should be considered. Fluids, electrolytes and protein replacement should be provided when indicated. Drugs which delay peristalsis, e.g. opiates and diphenoxylate with atropine may prolong and/or worsen the condition and should not be used.
Patients should be advised that nitrofurantoin may cause brownish discolouration of the urine.

Use in the elderly.

No data available.

Paediatric use.

Nitrofurantoin should not be administered to infants under one month of age. For information regarding dosage in children see Section 4.2 Dose and Method of Administration.

Effects on laboratory tests.

Nitrofurantoin can interfere with certain laboratory tests e.g. serum bilirubin (false positive or spuriously high reading), urine creatinine (false positive, or accurate readings cannot be made, due to interference), serum urea (no accurate reading due to interference), urine glucose (false positive or spuriously high readings). Urine glucose tests dependent on glucose oxidase are not affected e.g. Clinistix and Testape.

4.5 Interactions with Other Medicines and Other Forms of Interactions

The excretion of nitrofurantoin is decreased by acidifying drugs, whereby potentiation of nitrofurantoin may occur. Conversely, alkalinising drugs increase the rate of excretion and may diminish the effect of nitrofurantoin. Phenobarbitone has an inhibitory action on nitrofurantoin. Uricosuric drugs, such as probenecid and sulfinpyrazone, can inhibit renal tubular secretion of nitrofurantoin. The resulting increase in nitrofurantoin serum levels may increase toxicity and the decreased urinary levels could lessen its efficacy as a urinary tract antibacterial.
Antacids reduce the potency of the drug. Patients should be advised not to use antacid preparations at the same time as nitrofurantoin.

4.6 Fertility, Pregnancy and Lactation

Effects on fertility.

Rats given large doses of nitrofurantoin have developed lesions in seminiferous tubules which vary from atrophy to arrest of spermatogenesis. The arrest of spermatogenesis was reversible and treated male rats sired normal litters after recovery. In man, nitrofurantoin can decrease sperm counts and produce abnormal testicular histology suggestive of arrested spermatogenesis.
(Category A)

Short term therapy.

Nitrofurantoin has had widespread clinical use for many years. Studies, to date, have not shown a potential for nitrofurantoin to cause birth defects. Nitrofurantoin crosses the placenta, and caution should be exercised when administering nitrofurantoin at term or to infants under one month of age because of the possibility of producing a haemolytic anaemia in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency due to immature enzyme systems in the early neonatal period.
Although studies have shown that the amount of nitrofurantoin excreted in breast milk after normal therapeutic doses is negligible, the possibility of producing a haemolytic anaemia due to immature enzyme systems in the early neonatal period should be considered when administering the drug to nursing mothers.

4.7 Effects on Ability to Drive and Use Machines

Nitrofurantoin may cause dizziness and drowsiness and the patient should not drive or operate machinery if affected this way.

4.8 Adverse Effects (Undesirable Effects)

Gastrointestinal.

Nausea with associated anorexia and emesis is the most common adverse effect of nitrofurantoin therapy. This can be reduced by taking the drug with food or milk. Less frequent are abdominal pain and diarrhoea and, rarely, hepatitis - these latter dose-related toxic effects can be minimised by reduction of the dose especially in females on long term treatment. Dyspepsia, flatulence and constipation have also been reported.

Neurological.

Polyneuropathy, (including optic neuritis) which starts peripherally with initial sensory loss and paraesthesia but progresses to motor loss often with severe muscle atrophy, has occurred during nitrofurantoin therapy. A predisposing condition in most of these patients was renal failure which often was accompanied by anaemia, diabetes, electrolyte imbalance, vitamin B deficiency and debilitating disease. After stopping nitrofurantoin therapy, further deterioration is generally halted and total or partial regression occurs in almost 80% of those affected. These reactions may be severe or irreversible, but are rarely fatal. Polyneuropathy occurs in adults and children.
If numbness or tingling occurs in any area, administration of the drug should be discontinued. Headache, dizziness, nystagmus, drowsiness, asthenia, vertigo, amblyopia, depression, euphoria, confusion, psychotic reactions and benign intracranial hypertension have also been reported.

Hepatic.

Hepatic reactions can occur, including hepatitis, cholestatic jaundice, chronic active hepatitis and hepatic necrosis. These reactions can be life threatening, therefore, if they occur treatment should be stopped immediately. Chronic hepatic reactions can develop insidiously, but usually occur in patients on therapy for 5 months or longer. Patients on prolonged therapy should be re-examined at intervals not exceeding 6 months.

Hypersensitivity reactions of several types have been reported.

a) Pulmonary hypersensitivity.

Can be acute, sub-acute or chronic. These reactions can be life threatening; therefore, if they occur treatment should be stopped immediately.
Acute reactions are commonly manifested by fever, chills, cough, chest pain, dyspnoea and pulmonary infiltration with consolidation and pleural effusion on X-ray and eosinophilia. The acute reaction usually occurs in the first week of therapy and resolves on withdrawal of the drug.
Sub-acute or chronic pulmonary reactions are associated with prolonged therapy. Insidious onset of malaise, dyspnoea on exertion, cough, cyanosis, altered pulmonary function and roentgenographic and histological findings of diffuse interstitial pneumonitis and fibrosis are common manifestations. Patients on prolonged therapy should be re-examined at intervals not exceeding 6 months.
The severity of chronic pulmonary reactions and their degree of resolution appear to be related to the duration of therapy after the first clinical signs appear. Pulmonary function may be impaired permanently, even after cessation of therapy. The risk is greater when chronic pulmonary reactions are not recognised early.
Changes in ECG may occur associated with pulmonary reactions. Cardiopulmonary failure leading to collapse and death has been reported.

b) Dermatological reactions.

Exfoliative dermatitis, erythema multiforme, (including Stevens-Johnson syndrome) maculopapular, erythematous or eczematous eruptions and transient alopecia may occur.

c) Other sensitivity reactions.

Have included Lupus like syndrome and anaphylaxis, asthma attacks in patients with a history of asthma, urticaria, rash, pruritus, drug fever, angioedema, drug allergy, sialadenitis, pancreatitis and arthralgia.

Haematological reactions.

Haemolytic anaemia, leucopenia, granulocytopenia, eosinophilia, thrombocytopenia, agranulocytosis, aplastic anaemia and megaloblastic anaemia. Return of the blood picture to normal has followed cessation of therapy.

Miscellaneous reactions.

As with other microbial agents, urinary tract superinfections by resistant organisms (e.g. Pseudomonas or Candida) can occur. There are sporadic reports of Clostridium difficile superinfections, or pseudomembranous colitis, with the use of nitrofurantoin.
The most frequent laboratory test abnormalities reported with use of nitrofurantoin are as follows: eosinophilia, increased AST (SGOT), increased ALT (SGPT), decreased haemoglobin, increased serum phosphate.
The following laboratory adverse events also have been reported with the use of nitrofurantoin: glucose-6-phosphate dehydrogenase deficiency anaemia (see Section 4.4 Special Warnings and Precautions for Use), agranulocytosis, leukopenia, granulocytopenia, haemolytic anaemia, thrombocytopenia, megaloblastic anaemia. In most cases, these hematologic abnormalities resolved following cessation of therapy. Aplastic anaemia has been reported rarely.

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

There are very little data available on toxicity of nitrofurantoin after overdose. No toxic serum levels have been established.

Symptoms.

Symptoms expected would be mainly extensions of side effects. Occasional incidents of acute overdosage have not resulted in any specific symptoms other than vomiting.

Treatment.

There is no specific treatment of overdosage and no antidotes are recommended. Treatment is essentially symptomatic and supportive.
As nitrofurantoin is excreted rapidly in the urine administration of adequate amounts of fluid will hasten excretion of the absorbed drug. In a patient with normal renal function 50 to 250 mg/L are considered normal urine levels after taking a therapeutic dose.
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.

Nitrofurantoin is bacteriostatic at low concentrations (1:100,000 to 1:200,000) and in vitro is considered to be bactericidal in higher concentrations. Its presumed mode of action is based upon its interference with several bacterial enzyme systems.
Nitrofurantoin is active against Gram-positive and Gram-negative urinary tract pathogens, particularly E. coli, but Ps. aeruginosa and some Klebsiella, Aerobacter and Proteus strains are insensitive. See Table 1.

Urine levels reached with normal therapeutic doses are usually in the range of 15-46 microgram/mL and levels above the MIC for the most sensitive organisms are detectable for about 6 hours.
Bacteria develop only a limited resistance to furan derivatives.

Clinical trials.

No data available.

5.2 Pharmacokinetic Properties

Absorption.

Nitrofurantoin is well absorbed orally. The peak plasma level appears 1-2 hours after an oral dose and has been found not to exceed 2.5 microgram/mL.

Distribution.

25-60% of nitrofurantoin is bound to serum proteins. The plasma half life of the drug is 20 min. The average urinary drug recoveries following a therapeutic dose regimen (100 mg four times daily for 7 days) were reported to be 37.9% (day 1) and 35% (day 7) for the macrocrystalline dosage form.

Metabolism and excretion.

Nitrofurantoin is excreted rapidly in the urine, mainly in the unchanged form, the only metabolic pathway of importance involving reduction of the nitro group. Excretion is via the kidney both in the glomerular filtrate and by tubular secretion.

5.3 Preclinical Safety Data

Genotoxicity.

It may be concluded that although nitrofurantoin has genotoxic properties in vitro, it is of low genotoxic potential in whole animals. Thus, it is unlikely that the increased tumour incidences seen in male rats are due to genotoxic action.

Carcinogenicity.

Nitrofurantoin has caused increases in the incidence of renal tubular cell adenomas when administered to male rats at 65-125 mg/kg/day for 2 years. The biological significance of this remains to be established. When administered to female mice at 375 mg/kg/day for 2 years, nitrofurantoin induced an increase in the incidence of benign ovarian tumours. It would appear that this effect may be secondary to its primary toxic activity of inducing ovarian atrophy and sterility.

Mutagenicity.

Nitrofurantoin is mutagenic in certain bacterial systems and although it is not known how far this relates to the clinical situation the possibility of a permanent mutagenic effect on spermatozoa-producing cells requires that careful consideration be given to its use in young males.

6 Pharmaceutical Particulars

6.1 List of Excipients

Lactose monohydrate, pregelatinized starch and purified talc.
The capsule shells contain gelatin, titanium dioxide, quinoline yellow, iron oxide yellow, sodium lauryl sulfate and black ink TEK SW 9008.

6.2 Incompatibilities

See Section 4.5 Interactions with Other Medicines and Other Forms of Interactions.

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

PVC/Aluminium blisters of 3 x 10 capsules per carton (30s).

6.6 Special Precautions for Disposal

In Australia, any unused medicine or waste material should be disposed of in accordance with local requirements.

6.7 Physicochemical Properties

Nitrofurantoin is a synthetic antibacterial nitrofuran derivative. It occurs as lemon yellow crystals, or fine powder, and is very slightly soluble in water or alcohol. However, solubility of the drug in water and urine increases with rises in pH. Nitrofurantoin darkens on exposure to light or to alkali and is decomposed upon contact with metals other than stainless steel or aluminium. In view of this, the drug should not be exposed to light.

Note.

Nitrofurantoin (macrocrystals) is a larger crystal form of nitrofurantoin. The absorption of nitrofurantoin is slower and the excretion of nitrofurantoin is somewhat less, when the two are compared. The reduced incidence of gastrointestinal intolerance with nitrofurantoin is probably due to delayed and decreased absorption; this however does not significantly reduce clinical effectiveness. A number of patients who cannot tolerate nitrofurantoin tablets can take nitrofurantoin capsules without nausea.

Chemical structure.

Nitrofurantoin has the following chemical structure:

Chemical name: 1-(5-nitrofurfurylideneamino) hydantoin.
Molecular formula: C₈H₆N₄O₅.
Molecular weight: 238.2.

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ARX-Nitrofurantoin 100 mg Capsules

ARX-Nitrofurantoin 50 mg Capsules