INFORMATION FOR HEALTH PROFESSIONALS
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ALPHA-AMOXI 250mg capsules are yellow (size 2 capsules), imprinted '250'. Each capsule contains amoxicillin trihydrate equivalent to 250mg of amoxicillin, and typically weighs 367mg.
ALPHA-AMOXI 500mg capsules are yellow and brown (size 0 elongated capsules), imprinted '500'. Each capsule contains amoxicillin trihydrate equivalent to 500mg of amoxicillin, and typically weighs 713mg.
APO-AMOXI 125mg/5mL suspension is a white powder which when reconstituted with water forms an orange suspension with a frutti tutti flavour. Each 5mL of reconstituted suspension contains amoxicillin trihydrate equivalent to 125mg of amoxicillin.
APO-AMOXI 250mg/5mL suspension is a white powder which when reconstituted with water forms an orange suspension with a frutti tutti flavour. Each 5mL of reconstituted suspension contains amoxicillin trihydrate equivalent to 250mg of amoxicillin.
Amoxicillin is a bactericidal penicillin active against both Gram-positive and Gram-negative organisms and is subject to the hydrolytic activity of penicillinase. Amoxicillin differs in vitro from benzylpenicillin in the Gram-negative spectrum.
In vitro most strains of Haemophilus influenzae, Neisseria gonorrhoeae, N. meningitidis, Proteus mirabilis, Salmonellae, alpha- and beta-haemolytic Streptococci, Diplococcus pneumoniae, nonpenicillinase producing Staphylococci and Streptococcus faecalis, are sensitive to amoxicillin at serum concentrations which may be expected following the recommended doses. However, some of the organisms are sensitive to amoxicillin only at concentrations achieved in the urine (see Indications).
Escherichia coli isolates are becoming increasing resistant to amoxicillin in vitro due to the presence of penicillinase producing strains.
Strains of gonococci that are relatively resistant to benzylpenicillin may be sensitive to amoxicillin.
Amoxicillin is not effective against penicillinase producing bacteria, particularly resistant Staphylococci, which now have a high prevalence.
All strains of Pseudomonas, Klebsiella, Enterobacter, indole positive Proteus, Serratia marcescens, Citrobacter, penicillinase producing N. gonorrhoeae and penicillinase producing H. influenzae are also resistant.
Combining amoxicillin with a beta-lactamase inhibitor such as clavuanic acid effectively broadens its spectrum of activity to include many strains of beta-lactamase producing bacteria.
Like benzylpenicillin, amoxicillin is bactericidal against sensitive organisms during the stage of active multiplication. Amoxicillin exerts its mode of action by interfering with bacterial cell wall synthesis by acylating the enzyme transpeptidase, thus rendering it unable to cross-link muramic acid containing peptidoglycan strands. This inhibition of the biosynthesis of dipeptidoglycan, a substance necessary for cell wall strength and rigidity, results in a defective cell wall.
Amoxicillin is stable at gastric pH. It is completely absorbed in the upper gastrointestinal tract. Absorption is independent of meals.
Amoxicillin diffuses rapidly into most body tissues and fluids except for the brain and spinal fluid unless the meninges are inflamed. Amoxicillin has been shown to diffuse into saliva and sputum and is excreted mainly via the urine where it exists in high concentration. The amount to be found in bile is variable depending on normal biliary secretory function.
Amoxicillin is not highly protein bound, with only 17% protein bound in serum.
The serum half-life of amoxicillin is 61.3 minutes but in the absence of renal function it is 7 to 10 hours. The half-life may be longer in neonates and the elderly.
Oral doses of 250mg and 500mg of amoxicillin give average peak serum levels in one to two hours or 5micrograms/mL and 6.6 to 10.8micrograms /mL respectively. Detectable serum levels of amoxicillin are present 8 hours after the ingestion of a single dose.
Amoxicillin is primarily excreted by the renal system and approximately 75% of a 1g dose is excreted within 6 hours in the presence of normal renal function. It is excreted in the urine both unchanged (60%) and as penicilloic acid (15%). However, only about 32% of a 3g dose is excreted via the urine as the biologically active component in 8 hours (by which time most of the urinary excretion is complete). This proportional difference in the amount excreted from the different doses reflects a lack of linearity between doses and extent of absorption with a levelling off at higher doses or oral amoxicillin. Excretion of amoxicillin can be delayed by concurrent administration of probenecid thus prolonging its therapeutic effect.
Amoxicillin is indicated for the treatment of the following infections due to susceptible strains of sensitive organisms:
Upper Respiratory Infections: Otitis media, pharyngitis, sinusitis and tonsillitis.
Lower Respiratory Infections: Bronchitis, bronchopneumonia and lobar pneumonia.
Urinary Tract Infections: Cystitis, cysto-pyelitis, urethritis, and gonococcal urethritis.
Prophylaxis: against α-haemolytic (viridans group) and β-haemolytic Streptococci before dental, oral or upper respiratory tract surgery or instrumentation.
Prophylaxis: of bacterial endocarditis in patients with any of the following conditions: congenital cardiac malformations, rheumatic and other acquired valvular lesions, prosthetic heart valves, previous history of bacterial endocarditis, hypertrophic cardiomyopathy, surgically constructed systemic-pulmonary shunts, mitral valve prolapse with valvular regurgitation or mitral valve prolapse without valvular regurgitation but associated with thickening and/or redundancy of the valve leaflets.
Amoxicillin is further indicated for the treatment of cutaneous infections. In emergency cases where the causative organism is not yet identified, therapy may be initiated with amoxicillin on the basis of clinical judgement, while awaiting the results of bacteriologic studies to determine its antimicrobial sensitivity.
Amoxicillin can be administered orally independent of meals. Therapy should be maintained for a minimum for 5 days. Treatment should be continued for a minimum of 96 hours beyond the time the patient becomes asymptomatic or after evidence of bacterial eradication is observed. At least 10 days treatment is recommended for any infection caused by beta-haemolytic streptococci to prevent the occurrence of acute rheumatic fever or glomerulonephritis.
Adults: 250 mg every 8 hours.
Children < 20 kg: 25 mg/kg/day in divided doses every 8 hours.
In severe infections or infections associated with organisms where sensitivity determinations require higher blood concentrations :
Adults: 500 mg every 8 hours.
Children < 20 kg: 50 mg/kg/day in divided doses every 8 hours; this dosage should not exceed the recommended adult dosage.
Adults: 500 mg every 8 hours.
Children <20 kg: 50 mg/kg/day in divided doses every 8 hours; this dosage should not exceed the recommended adult dosage.
High Dosage Therapy: An adult dosage of 3g twice daily is recommended in appropriate cases for the treatment of severe or recurrent purulent infection of the respiratory tract.
Adults and children > 45 kg: 3 g as a single oral dose; 1 g of oral probenecid should be administered concomitantly as well as appropriate therapy for presumptive or proven infection with C. trachomatis.
Children < 45 kg: a single 50 mg/kg dose (maximum 3 g) of amoxicillin given with a single 25 mg/kg (up to 1 g) dose of probenecid. However, probenecid is not recommended in children under 2 years of age. Appropriate therapy of presumptive or proven infection with C. trachomatis should be included as well.
Before prescribing amoxicillin, dark field examinations should be carried out in those cases where syphilis is also suspected and monthly serologic tests should be carried out for a minimum of 4 months.
Adults: 3g as a single dose.
In the treatment of chronic urinary tract infections, frequent bacteriologic and clinical evaluations are necessary. Doses smaller than those recommended above should not be used. In stubborn infections, therapy may be required for several weeks, sometimes at doses higher than those recommended. Concurrent bacteriologic sensitivity monitoring is recommended. It may be necessary to continue clinical and/or bacteriologic follow-up for several months after cessation of therapy.
Adults: 3 g orally one hour before the procedure. A second dose may be given 6 hours later if considered necessary.
Children: For children under 5 administer quarter the adult dose and for children aged 5 to 10 administer half the adult dose.
Adults: 3g orally 4 hours prior to anaesthesia followed by 3g orally 6 hours after the initial dose.
Children: For children under 5 administer quarter the adult dose and for children aged 5 to 10 administer half the adult dose.
Note: The children's dose is intended for individuals whose weight will not cause dosage to be calculated greater than that recommended for adults. Children weighing more than 20 kg should be dosed according to the adult recommendations.
The relative dose interval for amoxicillin is 4 hours; thus, in patients with renal failure in whom the half life is 6 hours the dosage interval is 24 hours and it may be necessary to reduce the total daily dosage. In patients with a creatinine clearance of more than 30mL/min no dosage adjustment is required. For patients with a creatinine clearance between 10 and 30mL/min the maximum recommended dose is 500mg twice daily. For patients with a creatinine clearance of less than 10mL/min the maximum recommended dose is 500mg per day. In patients receiving peritoneal dialysis the maximum recommended daily dose is 500mg. Amoxicillin may be removed from the system by haemodialysis.
Patients with a history of hypersensitivity to beta-lactam antibiotics (e.g. penicillins and cephalosporins).
Amoxicillin is not effective against beta-lactamase-producing (penicillin resistant) staphylococci.
Serious and occasionally fatal hypersensitivity (anaphylactoid) reactions have been reported in patients on parenteral and oral penicillin therapy. These reactions, however, are more likely to occur in individuals with a history of sensitivity to multiple allergens. Therefore, before initiating therapy with amoxicillin or any penicillin, careful inquiry should be made concerning previous hypersensitivity reactions to penicillins, cephalosporins or other allergens. If an allergic reaction occurs, amoxicillin should be discontinued and the appropriate measures instituted. Serious anaphylactoid reactions require immediate emergency treatment with epinephrine, oxygen, intravenous steroids and airway management, as indicated.
As with other penicillins, amoxicillin should be administered with caution in the presence of renal or hepatic insufficiency. Periodic assessment of renal, hepatic and haematopoietic functions should be made during prolonged amoxicillin therapy. Since amoxicillin is excreted mainly by the kidney, the dosage for patients with renal impairment should be reduced when creatinine clearance is <30 mL/min (see Dosage and Administration).
The possibility of superinfections with mycotic organisms or bacterial pathogens should be kept in mind during amoxicillin therapy. If superinfections occur (usually involving Aerobacter, Candida or Pseudomonas), the drug should be discontinued and appropriate measures instituted.
Amoxicillin should not be used if infectious mononucleosis or lympathic leukaemia is suspected since the occurrence of a morbilliform rash in patients with infectious mononucleosis following the use of amoxicillin is well documented. These patients are also very susceptible to ampicillin-induced skin rashes.
Following single dose therapy of acute lower urinary tract infections, the urine should be cultured. A positive culture may be evidence of a complicated or upper urinary tract infection and call for a longer or larger course of therapy.
Adequate fluid intake and urinary output must be maintained in patients receiving high doses of amoxicillin.
Category A.
Animal studies with amoxicillin have not shown any teratological effects. The product has been used extensively for more than twenty years and its suitability in human pregnancy has been well documented. When antibiotic therapy is required during pregnancy, amoxicillin may be considered appropriate.
Amoxicillin is distributed into breast milk in low concentrations and should be used with caution in nursing women.
As with other penicillins, the most common adverse reactions observed with amoxicillin are related to sensitisation.
The following adverse reactions have been observed:
Hypersensitivity Reactions: Urticaria, puritus and erythematous maculopapular rashes. On rare occasions skin reactions such as erythema multiforme and Stevens-Johnson syndrome, toxic epidermal necrolysis and bullous and exfoliative dermatitis have been reported.
Severe allergic reactions including angioneurotic oedema, anaphylaxis, serum sickness, hypersensitivity vasculitis and interstitial nephritis have been reported rarely.
Amoxicillin treatment should be discontinued if reactions occur. Antihistamines and if necessary systematic corticosteriods can control reactions of urticaria, other skin rashes and serum sickness.
Liver: A moderate rise in serum glutamic oxaloacetic transaminase (SGOT) has been noted, but the significance of this finding is unknown. Hepatitis and cholestatic jaundice have been reported.
Gastrointestinal : Nausea, diarrhoea, intestinal candidasis and vomiting. Pseudomembraneous colitis has been reported rarely.
Haemic and Lymphatic Systems: Anaemia, thrombocytopenia, thrombocytopenic purpura, eosinophilia, leucopenia and agranulocytosis have been reported during therapy with other penicillins. These reactions are usually reversible on discontinuation of therapy and are believed to be a hypersensitivity phenomena. Prolonged bleeding time and prothrombin time have also been reported rarely.
Probenecid decreases the renal tubular secretion of amoxicillin, and concurrent use may result in increased and prolonged blood levels of amoxicillin.
There is an increased risk of skin rashes in patients taking amoxicillin and allopurinol concurrently
Amoxicillin may reduce the efficiency of oral contraceptives and patients should be warned according.
Tetracyclines and other bacteriostatic drugs may interfere with the bactericidal effects of amoxicillin.
Serious toxicity is unlikely to occur. Acute ingestion of large doses may cause nausea, vomiting, diarrhoea and abdominal pain and should be treated symptomatically. Amoxicillin is removable from the circulation by haemodialysis. For all cases of suspected overdose appropriate supportive measures and symptomatic treatment are recommended.
Store below 25°C.
Protect from heat, light and moisture.
The reconstituted suspension may be stored in a refrigerator (between 2 and 8°C) for up to 14 days.
The suspension is reconstituted by adding 85mL water to each bottle of powder as supplied (20.4g) to provide 100mL of reconstituted suspension.
Prescription-Only Medicine
ALPHA-AMOXI 250 mg capsules:
Bottle packs of 100 and 500.
Blister packs of 20, 100, 500 and 1000.
ALPHA-AMOXI 500 mg capsules:
Bottle packs of 100 and 500.
Blister packs of 20, 100, 500 and 1000.
APO-AMOXI 125mg/5mL suspension:
Bottles of powder which when reconstituted with 85mL of water form 100mL of
suspension.
APO-AMOXI 250mg/5mL suspension:
Bottles of powder which when reconstituted with 85mL of water form 100mL of
suspension
Suspensions contain sorbitol, sodium saccharin, Sunset yellow colorant (CI 15985, E110) and Tutti frutti flavour.
Apotex NZ Ltd
32 Hillside Road
Glenfield, Auckland
Private Bag 102-995
North Shore Mail Centre
Tel: (09) 444-2073
Fax: (09) 444-2951
10 March 2000