Amoxicillin [Amoxil 500mg]

Drug Nomenclature

International Nonproprietary Names (INNs) in main languages (French, Latin, Russian, and Spanish):

Amoxicillin Sodium

Drug Nomenclature

INNs in main languages (French, Latin, Russian, and Spanish):

Pharmacopoeias

In China and Europe. European Pharmacopoeia, 6th ed., 2008 and Supplements 6.1 and 6.2 (Amoxicillin Sodium). A white or almost white, very hygroscopic powder. Very soluble in water; sparingly soluble in dehydrated alcohol; very slightly soluble in acetone. A 10% solution in water has a pH of 8.0 to 10.0. Store in airtight contain.

Amoxicillin Trihydrate

Drug Nomenclature

Note. Compounded preparations of amoxicillin may be represented by the following names:

• Co-amoxiclav x/y (BAN)—amoxicillin (as the trihydrate or the sodium salt) and potassium clavulanate; x andy are the strengths in milligrams of amoxicillin and clavulanic acid respectively
• Co-amoxiclav (PEN)—amoxicillin trihydrate and potassium clavulanate.

Pharmacopoeias

In China, Europe, International, Japan, US. European Pharmacopoeia, 6th ed., 2008 and Supplements 6.1 and 6.2 (Amoxicillin Trihydrate). A white or almost white, crystalline powder. Slightly soluble in water; very slightly soluble in alcohol; practically insoluble in fatty oils. It dissolves in dilute acids and in dilute solutions of alkali hydroxides. A 0.2% solution in water has a pH of 3.5 to 5.5. Store in airtight containers. The United States Pharmacopeia 31, 2008 (Amoxicillin). A white, practically odourless crystalline powder. Slightly soluble in water and in methyl alcohol; insoluble in carbon tetrachloride, in chloroform, and in benzene. pH of a 0.2% solution in water is between 3.5 and 6.0. Store in airtight containers.

Adverse Effects and Precautions

As for Ampicillin. The incidence of diarrhoea is less with amoxicillin than ampicillin. Hepatitis and cholestatic jaundice have been reported with amoxicillin plus clavulanic acid; the clavulanic acid component has been implicated. Erythema multi-forme, Stevens-John son syndrome, toxic epidermal necrolysis, and exfoliative dermatitis have also been attributed occasionally to the use of amoxicillin with clavulanic acid.

Breast feeding

Although amoxicillin is excreted in breast milk in small amounts, the American Academy of Pediatrics considers that it is usually compatible with breast feeding.

Effects on the liver

Hepatitis and cholestatic jaundice associated with the combination amoxicillin with clavulanic acid (co-amoxiclav) have been reported and by 1993 the UK CSM had received 138 reports of hepatobiliary disorders, 3 of which were fatal. It warned that, although usually reversible, the reaction often occurred after stopping therapy with a delay of up to 6 weeks. It appeared that the clavulanic acid was probably responsible. Retrospective analysis of cases reported in Australia and a cohort study in the UK found increasing age and prolonged treatment to be major risk factors for jaundice after co-amoxiclav; male sex is also a risk factor. By 1997 the CSM considered that cholestatic jaundice occurred with a frequency of about 1 in 6000 adult patients and that the risk of acute liver injury was about 6 times greater with co-amoxiclav than with amoxicillin alone. Therefore it recommended that co-amoxiclav should be reserved for bacterial infections likely to be caused by amoxicillin-resistant strains, and that treatment should not usually exceed 14 days.

Effects on the teeth

A report of tooth discoloration in 3 children associated with the use of amoxicillin with clavulanic acid

Sodium content

Eachg of amoxicillin sodium contains about 2.6 mmol of sodium.

Interactions

As for Ampicillin.

Antimicrobial Action

As for Ampicillin. Amoxicillin has been reported to be more active in vitro than ampicillin against Enterococcus faecalis, Helicobacter pylori, and Salmonella spp., but less active against Shigella spp. Amoxicillin is inactivated by beta lactamases and complete cross-resistance has been reported between amoxicillin and ampicillin. The spectrum of activity of amoxicillin may be extended by use with a beta-lacta-mase inhibitor such as clavulanic acid. As well as reversing resistance to amoxicillin in beta-lacta-mase-producing strains of species otherwise sensitive, clavulanic acid has also been reported to enhance the activity of amoxicillin against several species not generally considered sensitive. These have included Bacteroides, Legionella, and Nocardia spp., Haemophilus influenzae, Moraxella catarrhalis (Branhamella catarrhalis), and Burkholderia pseudomallei (Pseudomonas pseudomallei). However, Ps. aeruginosa, Serratia marcescens, and many other Gram-negative bacteria remain resistant. Transferable resistance has been reported in H. pylori.

Pharmacokinetics

Amoxicillin is resistant to inactivation by gastric acid. It is more rapidly and more completely absorbed than ampicillin when given orally. Peak plasma-amoxicillin concentrations of about 5 micrograms/mL have been observed 1 to 2 hours after a dose of 250 mg, with detectable amounts present for up to 8 hours. Doubling the dose can double the concentration. The presence of food in the stomach does not appear to diminish the total amount absorbed. Concentrations of amoxicillin after intramuscular injection are similar to those achieved with oral doses. About 20% is bound to plasma proteins and plasma half-lives of 1 to 1.5 hours have been reported. The half-life may be prolonged in neonates, the elderly, and patients with renal impairment; in severe renal impairment the half-life may be 7 to 20 hours. Amoxicillin is widely distributed at varying concentrations in body tissues and fluids. It crosses the placenta; small amounts are distributed into breast milk. Little amoxicillin passes into the CSF unless the meninges are inflamed. Amoxicillin is metabolised to a limited extent to penicilloic acid which is excreted in the urine. About 60% of an oral dose of amoxicillin is excreted unchanged in the urine in 6 hours by glomerular filtration and tubular secretion. Urinary concentrations above 300 micrograms/mL have been reported after a dose of 250 mg. Probenecid reduces renal excretion. Amoxicillin is removed by haemodialysis. High concentrations have been reported in bile; some may be excreted in the faeces.

Amoxicillin with clavulanic acid

The pharmacokinetics of amoxicillin and clavulanic acid are broadly similar and neither appears to affect the other to any great extent.

Uses and Administration

Amoxicillin is the 4-hydroxy analogue of ampicillin and is used similarly in susceptible infections. These include actinomycosis, anthrax, biliary-tract infections, bronchitis, endocarditis (particularly for prophylaxis), gastro-enteritis (including salmonella enteritis, but not shigellosis), gonorrhoea, Lyme disease, mouth infections, otitis media, pneumonia, spleen disorders (pneumococcal infection prophylaxis), typhoid and paratyphoid fever, and urinary-tract infections. The beta-lactamase inhibitor clavulanic acid widens amoxicillin’s antimicrobial spectrum and a combined preparation (co-amoxiclav) can be used when resistance to amoxicillin is prevalent, for example in respiratory-tract infections due to Haemophilus influenzae or Moraxella catarrhalis (Branhamella catarrhalis), in the empirical treatment of animal bites, or in melioidosis. For details of these infections and their treatment, see under Choice of Antibacterial. Amoxicillin is also given as part of treatment regimens to eradicate Helicobacter pylori infection in patients with peptic ulcer disease.

Administration and dosage

Amoxicillin is given orally as the trihydrate and by injection as the sodium salt. Doses are expressed in terms of the equivalent amount of amoxicillin; 1.06 g of amoxicillin sodium and 1.15 g of amoxicillin trihydrate are each equivalent to about 1 g of amoxicillin. The usual oral dose is 250 to 500 mg every 8 hours, or 500 to 875 mg every 12 hours. Children up to 10 years of age may be given 125 to 250 mg every 8 hours; for those under 40 kg, a dose of 20 to 40 mg/kg daily in divided doses every 8 hours, or 25 to 45 mg/kg daily in divided doses every 12 hours, may be used; in infants less than 3 months old, the maximum dose should be 30 mg/kg daily in divided doses every 12 hours. Higher oral doses of amoxicillin, either as a single dose or in short courses, are used in some conditions. For example, a dose of 3 g repeated once after 8 hours may be used for dental abscesses. A 3-g dose may be given for uncomplicated acute urinary-tract infections, and repeated once after 10 to 12 hours. A high-dose regimen of 3 g twice daily may be used in patients with severe or recurrent infections of the respiratory tract. If necessary, children aged 3 to 10 years with otitis media may be given 750 mg twice daily for 2 days. Amoxicillin has also been given as a single dose of 3 g, with probenecid 1 g, in the treatment of uncomplicated gonorrhoea in areas where gonococci remain sensitive. For the prophylaxis of endocarditis in patients at risk, amoxicillin 2 or 3 g is given about 1 hour before dental procedures. For the eradication of H. pylori, amoxicillin is given with either metronidazole or clarithromycin and a proton pump inhibitor; usual doses of amoxicillin are 0.75 or 1 g twice daily or 500 mg three times daily. An extended release formulation containing 775 mg of amoxicillin as the trihydrate is available in the USA for the treatment of tonsillitis and pharyngitis due to Streptococcus pyogenes in patients aged 12 years or older. It is given orally in a dose of 115 mg daily for 10 days. Amoxicillin is given by intramuscular or slow intravenous injection in doses of 500 mg every 8 hours. In severe infections, 1 g of amoxicillin may be given every 6 hours by slow intravenous injection over 3 to 4 minutes or by infusion over 30 to 60 minutes. Children up to 10 years of age may be given 50 to 100 mg/kg daily by injection in divided doses. Doses may need to be reduced in moderate to severe renal impairment (see below).

Amoxicillin with clavulanic acid

Amoxicillin combined with clavulanic acid (co-amoxiclav) is given by mouth in a ratio of amoxicillin (as the trihydrate) 2, 4, 7, or 14 parts to 1 part of clavulanic acid (as the potassium salt), or intravenously in a ratio of 5 parts of amoxicillin (as the sodium salt) to 1 part of clavulanic acid (as the potassium salt). Doses of the combination, calculated on amoxicillin content, are similar to those for amoxicillin used alone.

Administration in renal impairment

Doses of amoxicillin should be reduced in patients with moderate to severe renal impairment according to creatinine clearance (CC):

• CC 10 to 30 mL/minute: 250 to 500 mg every 12 hours
• CC less than 10 mL/minute: 250 to 500 mg every 24 hours
• haemodialysis patients: 250 to 500 mg every 24 hours and an additional dose both during and after the dialysis session.

Preparations

British Pharmacopoeia 2008:

Amoxicillin Capsules; Amoxicillin Injection; Amoxicillin Oral Suspension; Co-amoxiclav Injection; Co-amoxiclav Tablets

The United States Pharmacopeia 31, 2008:

Amoxicillin and Clavulanate Potassium for Oral Suspension; Amoxicillin and Clavulanate Potassium Tablets; Amoxicillin Capsules; Amoxicillin for Oral Suspension; Amoxicillin Tablets; Amoxicillin Tablets for Oral Suspension

Single-ingredient Preparations

Multi-ingredient Preparations

Synonyms of Amoxicillin:

AMC, Amoxicilina [INN-Spanish], Amoxicillin Anhydrous, Amoxicillin Trihydrate, Amoxicilline [INN-French], Amoxicillinum [INN-Latin], Amoxycillin, Amoxycillin Trihydrate, D-Amoxicillin, P-Hydroxyampicillin

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Therapeutic classes of Amoxicillin:

Anti-Bacterial Agents, Penicillins

Delivery

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