Notes
Distributed by Wagner Pharmaceuticals Pty Ltd
1 Name of Medicine
Amoxicillin trihydrate and potassium clavulanate.
2 Qualitative and Quantitative Composition
Amoxicillin/Clavulanic Acid-WGR 500/125 and Amoxicillin/Clavulanic Acid-WGR 875/125 tablets (amoxicillin and clavulanic acid tablets) are combination products containing the semisynthetic antibiotic, amoxicillin (as the trihydrate) and the β-lactamase inhibitor, potassium clavulanate (as the potassium salt of clavulanic acid).
Each film coated tablet contains 500 mg amoxicillin as the trihydrate and 125 mg clavulanic acid as the potassium salt.
Each film coated tablet contains 875 mg amoxicillin as the trihydrate and 125 mg clavulanic acid as the potassium salt.
For the full list of excipients, see Section 6.1 List of Excipients.
3 Pharmaceutical Form
Amoxicillin/Clavulanic Acid-WGR 500/125 tablets.
A white, oval shaped, film coated tablet with marking "CA625" on one side.
Amoxicillin/Clavulanic Acid-WGR 875/125 tablets.
A white elongated capsule shaped film coated tablet.4.1 Therapeutic Indications
Amoxicillin/Clavulanic Acid-WGR 500/125 and Amoxicillin/Clavulanic Acid-WGR 875/125 tablets are indicated for short term treatment of bacterial infections at the following sites when caused by sensitive organisms (see Section 5.1 Pharmacodynamic Properties, Mechanism of action, Microbiology):
Urinary tract infections (uncomplicated and complicated);
Lower respiratory tract infections, including community acquired pneumonia and acute exacerbations of chronic bronchitis;
Upper respiratory tract infections, such as sinusitis, otitis media and recurrent tonsillitis;
Skin and skin structure infection.
Appropriate culture and susceptibility studies should be performed to identify the causative organism(s) and determine its (their) susceptibility to amoxicillin and clavulanic acid tablets. However, when there is reason to believe an infection may involve any of the β-lactamase producing organisms listed above, therapy may be instituted prior to obtaining the results from bacteriological and susceptibility studies. Once these results are known, therapy should be adjusted if appropriate.
The treatment of mixed infections caused by amoxicillin susceptible organisms and β-lactamase producing organisms susceptible to amoxicillin and clavulanic acid tablets should not require the addition of another antibiotic due to the amoxicillin content of these products.
4.2 Dose and Method of Administration
Amoxicillin/Clavulanic Acid-WGR 500/125 and Amoxicillin/Clavulanic Acid-WGR 875/125 tablets should be taken immediately before or with the first mouthful of food, to minimise potential gastrointestinal intolerance and to optimise absorption.
Adults.
The usual adult dose is one Amoxicillin/Clavulanic Acid-WGR 500/125 tablet every 12 hours. For more severe infections, the dose should be one Amoxicillin/Clavulanic Acid-WGR 875/125 tablet every 12 hours.
Note.
Since both Amoxicillin/Clavulanic Acid-WGR 875/125 and Amoxicillin/Clavulanic Acid-WGR 500/125 tablets contain the same amount of clavulanic acid (125 mg, as the potassium salt), two Amoxicillin/Clavulanic Acid-WGR 500/125 tablets are not equivalent to one Amoxicillin/Clavulanic Acid-WGR 875/125 tablet. Therefore, two Amoxicillin/Clavulanic Acid-WGR 500/125 tablets should not be substituted for one Amoxicillin/Clavulanic Acid-WGR 875/125 tablet for treatment of more severe infections.
Treatment should usually be continued for 48 to 72 hours beyond the time that the patient becomes asymptomatic or evidence of bacterial eradication has been obtained. Treatment should not exceed 14 days without review.
Renal impairment.
Amoxicillin/Clavulanic Acid-WGR 875/125 tablets should not be used in patients with moderate to severe renal impairment (creatinine clearance ≤ 30 mL/min).
Both amoxicillin and clavulanic acid are excreted by the kidneys and the serum half life of each increases in patients with renal failure. *No adjustment to the initial amoxicillin and clavulanic acid tablet dose is necessary, but the dosing interval should be extended according to the degree of renal impairment. See Table 1.
Haemodialysis decreases serum concentrations of both amoxicillin and clavulanic acid and an additional dose should be administered at the end of dialysis.
Children.
Children weighing 40 kg and more should be dosed according to the adult recommendations. It is recommended that amoxicillin and clavulanic acid suspensions be used for children weighing less than 40 kg.4.3 Contraindications
A history of allergic reaction to β-lactams e.g. penicillins or cephalosporins.
Previous history of amoxicillin/clavulanic acid-associated jaundice or hepatic dysfunction.
4.4 Special Warnings and Precautions for Use
Identified precautions.
Before initiating therapy with amoxicillin-clavulanate, careful enquiry should be made concerning previous hypersensitivity reactions to penicillins, cephalosporins or other allergens.
Serious and occasionally fatal hypersensitivity reactions (including anaphylactoid and severe cutaneous adverse reactions) have been reported in patients on penicillin therapy. Although anaphylaxis is more frequent following parenteral therapy, it has occurred in patients on oral penicillins. These reactions are more likely to occur in individuals with a history of penicillin hypersensitivity and/or a history of sensitivity to multiple allergens.
There have been reports of individuals with a history of penicillin hypersensitivity who have experienced severe reactions when treated with cephalosporins. Before initiating therapy with any penicillin, careful inquiry should be made concerning previous hypersensitivity reactions to penicillins, cephalosporins, or other allergens. Hypersensitivity reactions can also progress to Kounis syndrome, a serious allergic reaction that can result in myocardial infarction. Presenting symptoms of such reactions can include chest pain occurring in association with an allergic reaction to Augmentin (see Section 4.8 Adverse Effects (Undesirable Effects)). If an allergic reaction occurs, Amoxicillin/Clavulanic Acid-WGR should be discontinued and the appropriate therapy instituted. Serious anaphylactoid reactions require immediate emergency treatment with adrenaline. Oxygen, intravenous steroids, and airway management, including intubation, should also be administered as indicated.
Drug-induced enterocolitis syndrome (DIES) has been reported mainly in children receiving amoxicillin/clavulanate (see Section 4.8 Adverse Effects (Undesirable Effects)). DIES is an allergic reaction with the leading symptom of protracted vomiting (1-4 hours after administration of amoxicillin/clavulanate) in the absence of allergic skin or respiratory symptoms. Further symptoms could comprise abdominal pain, diarrhoea, hypotension or leucocytosis with neutrophilia. There have been severe cases including progression to shock.
Antibiotic associated pseudomembranous colitis has been reported with many antibiotics including amoxicillin. 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 antibiotic 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 (Lomotil) may prolong and/or worsen the condition and should not be used.
General.
As with any potent drug, periodic assessment of organ system functions, including renal, hepatic and haematopoietic function is advisable during prolonged therapy.
Since amoxicillin and clavulanic acid tablets contain amoxicillin, an aminopenicillin, these are not the treatment of choice in patients presenting with sore throat or pharyngitis because of the possibility that the underlying cause is infectious mononucleosis, in the presence of which there is a high incidence of rash if amoxicillin is used.
Amoxicillin and clavulanic acid tablets should be given with caution to patients with lymphatic leukaemia since they are especially susceptible to amoxicillin induced skin rashes.
Amoxicillin-clavulanate should be avoided if infectious mononucleosis is suspected since the occurrence of a morbilliform rash has been associated with this condition following the use of amoxicillin.
Prolonged use may also occasionally result in overgrowth of non-susceptible organisms.
Abnormal prolongation of prothrombin time (increased INR) has been reported rarely in patients receiving amoxicillin-clavulanate and oral anticoagulants. Appropriate monitoring should be undertaken when anticoagulants are prescribed concurrently. Adjustments in the dose of oral anticoagulants may be necessary to maintain the desired level of anticoagulation.
The possibility of superinfections with mycotic or bacterial pathogens should be kept in mind during therapy. If superinfections occur (usually involving Aerobacter, Pseudomonas or Candida), the drug should be discontinued and/or appropriate therapy instituted.
Cholestatic hepatitis, which may be severe but is usually reversible, has been reported rarely. Signs and symptoms may not become apparent until several weeks after treatment has ceased. In most cases resolution has occurred with time. However, in extremely rare circumstances, deaths have been reported. These have almost always been cases associated with serious underlying disease or concomitant medications. Hepatic events subsequent to amoxicillin and clavulanic acid tablets have occurred predominantly in males and elderly patients and may be associated with prolonged treatment. These events have been very rarely reported in children.
Use in hepatic impairment.
Amoxicillin and clavulanic acid tablets should be used with care in patients with evidence of hepatic dysfunction.
Data is currently insufficient for a dosage recommendation. Dose with caution, and monitor hepatic function at regular intervals.
Use in renal impairment.
In patients with reduced urine output, crystalluria (including acute renal injury) has been observed very rarely, predominantly with parenteral therapy. During the administration of high doses of amoxicillin, it is advisable to maintain adequate fluid intake and urinary output in order to reduce the possibility of amoxicillin crystalluria (see Section 4.8 Adverse Effects (Undesirable Effects); Section 4.9 Overdose).
Amoxicillin/Clavulanic Acid-WGR 875/125 tablets should not be used in patients with moderate to severe renal impairment (creatinine clearance ≤ 30 mL/min).
Amoxicillin/Clavulanic Acid-WGR 500/125 tablets should be used with care in patients with moderate or severe renal impairment. The dosage of Amoxicillin/Clavulanic Acid-WGR 500/125 should be adjusted as recommended in Section 4.2 Dose and Method of Administration.
Use in the elderly.
No data available.
Paediatric use.
See Section 4.2 Dose and Method of Administration.
Effects on laboratory tests.
Oral administration of amoxicillin and clavulanic acid tablets will result in high urine concentrations of amoxicillin. Since high urine concentrations of ampicillin may result in false positive reactions when testing for the presence of glucose in urine using Clinitest, Benedict's Solution or Fehling's Solution, it is recommended that glucose tests based on enzymatic glucose oxidase reactions (such as Clinistix or Testape) be used.
Following administration of ampicillin to pregnant women a transient decrease in plasma concentration of total conjugated oestriol, oestriol-glucuronide, conjugated oestrone and oestradiol has been noted. This effect may also occur with amoxicillin and therefore, amoxicillin and clavulanic acid tablets.4.5 Interactions with Other Medicines and Other Forms of Interactions
Probenecid decreases the renal tubular secretion of amoxicillin but does not affect clavulanic acid excretion. Concurrent use with amoxicillin and clavulanic acid tablets may result in increased and prolonged blood levels of amoxicillin but not of clavulanic acid.
The concurrent administration of allopurinol and ampicillin increases substantially the incidence of rashes in patients receiving both drugs as compared to patients receiving ampicillin alone. It is not known whether this potentiation of ampicillin rashes is due to allopurinol or the hyperuricemia present in these patients. There are no data with amoxicillin and clavulanic acid tablets and allopurinol administered concurrently.
No information is available about the concurrent use of amoxicillin and clavulanic acid tablets and alcohol. However, the ingestion of alcohol whilst being treated with some other beta-lactam antibiotics has precipitated a disulfiram (Antabuse) like reaction in some patients. Therefore, the ingestion of alcohol should be avoided during and for several days after treatment with amoxicillin and clavulanic acid tablets.
In common with other antibiotics, amoxicillin and clavulanic acid tablets may affect the gut flora, leading to lower oestrogen reabsorption and reduced efficacy of combined oral contraceptives. Patients should be warned accordingly.
In the literature there are rare cases of increased international normalised ratio in patients maintained on acenocoumarol or warfarin and prescribed a course of amoxicillin. If co-administration is necessary, the prothrombin time or international normalised ratio should be carefully monitored with the addition or withdrawal of amoxicillin.
Penicillins may reduce the excretion of methotrexate causing a potential increase in toxicity.
4.6 Fertility, Pregnancy and Lactation
Effects on fertility.
Amoxicillin/clavulanic acid at oral doses of up to 1200 mg/kg/day had no effect on fertility and reproductive performance in rats dosed with a 2:1 ratio formulation of amoxicillin and clavulanate.
(Category B1)
Animal studies with orally and parenterally administered amoxicillin and clavulanic acid tablets have shown no teratogenic effects. There is limited experience of the use of amoxicillin and clavulanic acid tablets in human pregnancy. In women with preterm, premature rupture of the foetal membrane (pPROM), prophylactic treatment with amoxicillin and clavulanic acid may be associated with an increased risk of necrotising enterocolitis in neonates. As with all medicines, use should be avoided in pregnancy, especially during the first trimester, unless considered essential by the physician.
Use in labour and delivery.
Oral ampicillin class antibiotics are generally poorly absorbed during labour. Studies in guinea pigs have shown that intravenous administration of ampicillin decreased the uterine tone, frequency of contractions, height of contractions and duration of contractions. However, it is not known whether the use of amoxicillin and clavulanic acid tablets in humans during labour or delivery has immediate or delayed adverse effects on the foetus, prolongs the duration of labour or increases the likelihood that forceps delivery or other obstetrical intervention or resuscitation of the newborn will be necessary.
Amoxicillin is excreted in the milk; there are no data on the excretion of clavulanic acid in human milk. Therefore, caution should be exercised when amoxicillin and clavulanic acid tablets are administered to a nursing woman.4.7 Effects on Ability to Drive and Use Machines
Adverse effects on the ability to drive or operate machinery have not been observed.
4.8 Adverse Effects (Undesirable Effects)
Amoxicillin and clavulanic acid tablets are generally well tolerated. The majority of events were of a mild and transient nature.
Clinical trials.
During clinical trials, the most frequently reported adverse events related or possibly related to amoxicillin and clavulanic acid 875/125 mg tablet therapy were diarrhoea (14.9%), nausea (7.9%), headache (6.8%), abdominal pain (4.5%), vomiting (3.8%), genital moniliasis (3.6%) and vaginitis (3.4%).
The following adverse events have been observed during clinical trials with amoxicillin and clavulanic acid 875/125 mg tablets, however, it should be noted that causality has not necessarily been established for these events (see Table 2):
During clinical trials, the most frequently reported adverse events related or possibly related to amoxicillin and clavulanic acid 500/125 mg tablet therapy were diarrhoea (12.8%), nausea (5.2%), headache (4.8%), abdominal pain (4.5%).
The following adverse events have been observed during clinical trials with amoxicillin and clavulanic acid 500/125 mg tablets, however, it should be noted that causality has not necessarily been established for these events (see Table 3):
Post marketing.
In addition, the following adverse reactions have been reported for ampicillin class antibiotics and may occur with amoxicillin and clavulanic acid 500/125 mg tablets and amoxicillin and clavulanic acid 875/125 mg tablets: very common ≥ 1/10, common ≥ 1/100 and < 1/10, uncommon ≥ 1/1,000 and < 1/100, rare ≥ 1/10,000 and < 1/1,000, very rare < 1/10,000, not known cannot be estimated from available data.
Infections and infestations.
Common: mucocutaneous candidiasis.
Cardiac disorders.
Not known: Kounis syndrome (see Section 4.4 Special Warnings and Precautions for Use).
Gastrointestinal disorders.
Very common: diarrhoea.
Common: nausea, vomiting.
Uncommon: indigestion.
Rare: gastritis, stomatitis, glossitis, black "hairy" tongue, enterocolitis, antibiotic-associated colitis (including pseudomembranous colitis and haemorrhagic colitis) (see Section 4.4 Special Warnings and Precautions for Use).
Not known: drug-induced enterocolitis syndrome, pancreatitis acute.
Hepatobiliary.
Uncommon: moderate rise in AST and/or ALT.
Rare: Hepatitis, cholestatic jaundice which may be severe but is usually reversible.
Nervous system disorders.
Uncommon: dizziness, headache.
Very rare: reversible hyperactivity, convulsions. Convulsions may occur in patients with impaired renal function or those receiving high doses.
Not known: aseptic meningitis.
Haematopoietic and lymphatic systems.
Uncommon: thrombocytosis.
Rare: anaemia, thrombocytopenia, thrombocytopenic purpura, eosinophilia, reversible leukopenia (including neutropenia or agranulocytosis) these are usually reversible on discontinuation of therapy and are believed to be hypersensitivity phenomena, prolongation of bleeding time and prothrombin time.
Hypersensitivity and skin.
Common: skin rashes, pruritus, urticaria.
Rare: angioneurotic oedema, anaphylaxis, serum-sickness-like syndrome, erythema multiforme, Stevens-Johnson syndrome, hypersensitivity, vasculitis, toxic epidermal necrolysis, bullous exfoliative dermatitis, acute generalised exanthematous putulosis (AGEP), drug reaction with eosinophilia and systemic symptoms (DRESS), and symmetrical drug-related intertriginous and flexural exanthema (SDRIFE) (baboon syndrome) have been reported rarely. Whenever such reactions occur, Amoxicillin/Clavulanic Acid-WGR 500/125 should be discontinued, unless in the opinion of the physician no alternative treatment is available and continued use of Amoxicillin/Clavulanic Acid-WGR 500/125 is considered essential. Serious and occasional fatal hypersensitivity (anaphylactic) reactions and angioneurotic oedema can occur with oral penicillins (see Section 4.4 Special Warnings and Precautions for Use).
Not known: linear IgA disease.
Renal and urinary tract disorders.
Rare: interstitial nephritis.
Not known: crystalluria (including acute renal injury) (see Section 4.9 Overdose).
Miscellaneous.
Rare: superficial tooth discolouration which can usually be removed by brushing.
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 http://www.tga.gov.au/reporting-problems.4.9 Overdose
Serious and severe clinical symptoms are unlikely to occur after overdosage with amoxicillin and clavulanic acid tablets. If encountered, gastrointestinal symptoms and disturbance of the fluid and electrolyte balances may be evident. They may be treated symptomatically, with attention to the water/electrolyte balance.
Amoxicillin crystalluria, in some cases leading to renal failure, has been observed (see Section 4.4 Special Warnings and Precautions for Use).
Amoxicillin may be removed from the circulation by haemodialysis.
For information on the management of overdose, contact the Poisons Information Centre on 131126 (Australia).
5 Pharmacological Properties
5.1 Pharmacodynamic Properties
Mechanism of action.
Microbiology. Like other penicillins, amoxicillin has a bactericidal effect on sensitive organisms during the stage of active multiplication. However, amoxicillin is susceptible to hydrolysis by β-lactamases and the addition of clavulanic acid in amoxicillin and clavulanic acid tablets extends the antimicrobial spectrum of amoxicillin to include organisms normally resistant to amoxicillin due to β-lactamase production. In vitro studies have demonstrated the susceptibility of most strains of the following organisms (see Tables 4, 5, 6, and 7):
The following in vitro data are available but their clinical significance is unknown (see Table 8).
Susceptibility testing. Diffusion technique.
For Kirby-Bauer method of susceptibility testing, a 30 microgram amoxicillin and clavulanic acid (20 microgram amoxicillin + 10 microgram clavulanic acid) diffusion disc should be used. With this procedure, a report from the laboratory of "Susceptible" indicates that the infecting organism is likely to respond to amoxicillin and clavulanic acid therapy and a report of "Resistant" indicates that the infecting organism is not likely to respond to therapy. An "Intermediate Susceptibility" report suggests that the infecting organism would be susceptible to amoxicillin and clavulanic acid if the infection is confined to tissues or fluids (e.g. urine) in which high antibiotic levels are attained.
Dilution techniques.
Broth or agar dilution methods may be used to determine the minimal inhibitory concentration (MIC) value susceptibility of bacterial isolates to amoxicillin and clavulanic acid. Tubes should be inoculated to contain 104 to 105 organisms/mL or plates "spotted" with 103 to 104 organisms.
The recommended dilution method employs a constant amoxicillin/clavulanic acid ratio of 2 to 1 in all tubes with increasing concentrations of amoxicillin. MICs are reported in terms of amoxicillin concentration in the presence of clavulanic acid at constant 2 parts amoxicillin to 1 part clavulanic acid. See Tables 9 and 10.
Clinical trials.
Amoxicillin and clavulanic acid (875/125 mg) tablets vs amoxicillin and clavulanic acid (500/125 mg) tablets.
Three pivotal studies in 1,361 patients treated for between 7 and 14 days for either lower respiratory tract infections, upper respiratory infections or complicated urinary tract infections compared a regimen of amoxicillin and clavulanic acid (875/125 mg) tablets every 12 hours (q12h) to amoxicillin and clavulanic acid (500/125 mg) tablets dosed every 8 hours (q8h) (584, 170 and 607 patients, respectively). Comparable efficacy was demonstrated between the q12h and q8h dosing regimens. There was no significant difference in the percentage of adverse events in each group. The most frequently reported adverse event in two of the studies was diarrhoea; incidence rates were similar for the 875/125 mg q12h and 500/125 mg q8h dosing regimens (14.9% and 14.3%, respectively). However, there was a statistically significant difference (p < 0.05) in rates of severe diarrhoea or withdrawals with diarrhoea between the regimens: 1.0% for 875/125 mg q12h dosing versus 2.5% for the 500/125 mg q8h dosing. In the third study the most frequently reported adverse event was headache with an incidence of 5.7% (amoxicillin and clavulanic acid (500/125 mg) tablets q8h) vs 8.3% (amoxicillin and clavulanic acid (875/125 mg) tablets q12h).
As noted previously although there was no significant difference in the percentage of adverse events in each group there was a statistically significant difference in rates of severe diarrhoea or withdrawals with diarrhoea between the regimens.
Amoxicillin and clavulanic acid (500/125 mg) tablets vs amoxicillin and clavulanic acid (250/125 mg) tablets.
Two pivotal studies in 908 patients treated for between 5 and 10 days for either uncomplicated Skin and Skin Structure Infections (SSSI) or Acute Exacerbation of Chronic Bronchitis (AECB) compared a regimen of amoxicillin and clavulanic acid (500/125 mg) tablets every 12 hours with amoxicillin and clavulanic acid (250/125 mg) tablets every 8 hours. Comparable efficacy was demonstrated between the 12 hourly and 8 hourly dosing regimens.
There was no significant difference in the percentage of adverse events in each group, with the most frequently reported adverse event in the two studies being diarrhoea.
The clinical efficacy of amoxicillin and clavulanic acid tablets given in a twice daily versus three times daily regimen have been shown to be comparable in AECB and SSSI, despite the differences in some pharmacokinetic parameters.
Given the similar TMIC and the demonstration of equivalence between AECB and SSSI it would be reasonable to extrapolate to the remaining indications. Clinical safety and efficacy in other indications were investigated, however, these supportive studies were not sufficiently designed to demonstrate the relative efficacy of the two amoxicillin and clavulanic acid tablets regimens, or compared the proposed regimen with other treatments.
5.2 Pharmacokinetic Properties
Absorption.
Amoxicillin and clavulanic acid tablets are stable in the presence of gastric acid. Their two components are rapidly absorbed if administered before or with a meal, but if given after meals, the serum levels of clavulanic acid are significantly reduced. To optimise absorption of clavulanic acid, amoxicillin and clavulanic acid tablets should be administered at the start of a meal. The pharmacokinetics of amoxicillin are not affected by food.
Oral administration of amoxicillin and clavulanic acid (875 mg/125 mg) tablets every 12 hours was compared with amoxicillin and clavulanic acid (500 mg/125 mg) tablets every 8 hours at the start of a light meal. The following mean pharmacokinetic parameters (Table 11 and 12) were observed for amoxicillin and clavulanic acid (875/125 mg) tablets taken every 12 hours and amoxicillin and clavulanic acid (500 mg/125 mg) tablets taken every 8 hours:
The half-life and Cmax for clavulanate for amoxicillin and clavulanic acid (875/125 mg) tablets were not significantly different from amoxicillin and clavulanic acid (500/125 mg) tablets. However, the AUC(0-24 hours) was reduced, as would be expected with the lower daily dose of clavulanate i.e. 250 mg in amoxicillin and clavulanic acid (875/125 mg) tablets vs 375 mg in amoxicillin and clavulanic acid (500/125 mg) tablets.
Oral administration of amoxicillin and clavulanic acid (500 mg/125 mg) tablets every 12 hours was compared with amoxicillin and clavulanic acid (250 mg/125 mg) every 8 hours at the start of a light meal.
The following mean pharmacokinetic parameters were observed for amoxicillin for amoxicillin and clavulanic acid (500/125 mg) tablets taken every 12 hours and amoxicillin and clavulanic acid (250 mg/125 mg) taken every 8 hours (see Tables 13 and 14):
Distribution.
Following oral administration, both amoxicillin and clavulanic acid have been shown to diffuse in significant concentrations into pus, bile, and pleural, synovial and peritoneal fluids. Both penetrate poorly into the cerebrospinal fluid (CSF) when the meninges are normal. Amoxicillin penetrates into the CSF better through inflamed meninges, but the maximum concentrations are still much lower than the peak serum levels. There are no data at present on the CSF penetration of clavulanic acid in patients with meningeal inflammation.
Neither amoxicillin nor clavulanic acid is highly protein bound. Clavulanic acid has been variously reported to be bound to human serum in the range of 9 - 30% and amoxicillin approximately 20% bound. From animal studies, there is no evidence to suggest either component accumulates in any organ.
Excretion.
As with other penicillins, renal excretion is the major route of amoxicillin clearance, while clavulanate elimination is via both renal and non-renal mechanisms. Approximately 70% of the dose of amoxicillin is excreted in urine as amoxicillin. For clavulanic acid, following the administration of 125 mg of radiolabelled potassium clavulanate orally to normal volunteers 68% of the administered radioactivity was recovered in the urine in 24 hours. Of this 34% (i.e. 23% of the administered dose) represented unchanged clavulanic acid. 2,5-dihydro-4-(2-hydroxyethyl)-5-oxo-1H-pyrrole-3-carboxylic acid (the major metabolite) and 1-amino-4-hydroxy-butan-2-one accounted for a further 23% and 12% (i.e. 16% and 8% respectively of the administered dose). Small amounts of other yet unidentified metabolites were also present. These metabolites were also present in the urine of rat and dog. The extent of urinary excretion of clavulanic acid and its metabolites is lower in rat urine than in dog and human urine.
Concurrent administration of probenecid delays amoxicillin excretion but does not delay renal excretion of clavulanic acid.
5.3 Preclinical Safety Data
Genotoxicity.
The genotoxic potential of amoxicillin/clavulanic acid was investigated in assays for chromosomal damage (mouse micronucleus test and a dominant lethal test) and gene conversion. All were negative.
Carcinogenicity.
Long-term studies in animals have not been performed to evaluate carcinogenic or mutagenic potential.6 Pharmaceutical Particulars
6.1 List of Excipients
Amoxicillin/Clavulanic Acid-WGR 500/125 tablets also contain the inactive ingredients: magnesium stearate, croscarmellose sodium, purified talc and microcrystalline cellulose. The tablet coating contains titanium dioxide, hypromellose, ethyl cellulose, hyprolose and propylene glycol.
Amoxicillin/Clavulanic Acid-WGR 875/125 tablets also contain the inactive ingredients: magnesium stearate, croscarmellose sodium, purified talc and microcrystalline cellulose. The tablet coating contains titanium dioxide, hypromellose, ethyl cellulose, hyprolose and propylene glycol.
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
Amoxicillin/Clavulanic Acid-WGR 500/125 and Amoxicillin/Clavulanic Acid-WGR 875/125 tablets should be stored below 25°C and protected from moisture.
6.5 Nature and Contents of Container
Amoxicillin/Clavulanic Acid-WGR 500/125 Tablets: Available as PVC-Al blister packs of 2, 10 and 60.
Amoxicillin/Clavulanic Acid-WGR 875/125 Tablets: Available as PVC/Al blister packs of 2, 10 and 60.
Not all pack sizes are being distributed in Australia.
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
Amoxicillin trihydrate.
Amoxicillin trihydrate is white to almost white, crystalline powder, slightly soluble in water and in alcohol, practically insoluble in ether and in fatty oils. It dissolves in dilute acids and dilute solutions of alkali hydroxides. It has a pKa of 2.8 and 7.2, with a partition coefficient of -2.69.
Chemical structure.
Chemically, amoxicillin trihydrate is (2S,5R,6R)-6-[[(2R)-2-amino-2-(4-hydroxyphenyl)acetyl] amino]- 3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid trihydrate. It is susceptible to hydrolysis by β-lactamases. Amoxicillin trihydrate may be represented structurally as:
Molecular formula: C16H19N3O5S.3H2O.
Molecular weight: 419.4.
CAS number.
61336-70-7.
Clavulanic acid.
Potassium clavulanate is white to almost white, crystalline powder, hygroscopic, freely soluble in water, slightly soluble in alcohol, and very slightly soluble in acetone. The pKa is 2.7, with a partition coefficient of -1.38.
Chemical structure.
Clavulanic acid is produced by the fermentation of Streptomyces clavuligerus. It is an irreversible inhibitor of many β-lactamase enzymes except type 1 (Richmond). It is a β-lactam compound with only weak antibacterial activity. Chemically, potassium clavulanate is potassium (2R,3Z,5R)-3-(2- hydroxyethylidene)-7-oxo-4-oxa-1-azabicyclo[3.2.0]heptane-2carboxylate, and may be represented structurally as:
Molecular formula: C8H8KNO5.
Molecular weight: 237.3.
CAS number.
61177-45-5.7 Medicine Schedule (Poisons Standard)
S4 - Prescription Only Medicine.
Summary Table of Changes
