Amoxicillin: Price, Dosage & Where to Buy

Amoxicillin is an aminopenicillin antibiotic used to treat bacterial infections of the ear, nose, throat, skin, genitourinary tract, and lower respiratory tract. In adults, it is also prescribed in combination therapy to eradicate Helicobacter pylori and treat duodenal ulcer disease. Amoxicillin requires a prescription in the United Kingdom and has been available as a generic medicine for many years.

Amoxicillin treats infections caused by susceptible bacteria that do not produce beta-lactamase enzymes. It is indicated for upper respiratory tract infections of the ear, nose, and throat caused by Streptococcus species, Streptococcus pneumoniae, Staphylococcus species, or Haemophilus influenzae. It treats genitourinary tract infections due to Escherichia coli, Proteus mirabilis, or Enterococcus faecalis.

Amoxicillin is used for skin and skin structure infections caused by Streptococcus species, Staphylococcus species, or E. coli, and for lower respiratory tract infections caused by Streptococcus species, S. pneumoniae, Staphylococcus species, or H. influenzae. In adults, amoxicillin is indicated in combination with clarithromycin and lansoprazole, or with lansoprazole alone, to treat Helicobacter pylori infection and duodenal ulcer disease. Eradication of H. pylori reduces the risk of duodenal ulcer recurrence.

Amoxicillin belongs to the beta-lactam class of antibiotics and works by interfering with bacterial cell wall synthesis. Bacteria need intact cell walls to survive and multiply. Amoxicillin binds to proteins in the bacterial cell wall and prevents the final step of cell wall construction.

Without a complete cell wall, the bacterial cell becomes weak and eventually ruptures, leading to bacterial death. This mechanism is effective only against bacteria that are actively growing and building new cell walls. Amoxicillin is active against a range of gram-positive and gram-negative bacteria, but it does not work against bacteria that produce beta-lactamase enzymes, which can break down the antibiotic before it can act.

The label lists capsules in 250 mg and 500 mg strengths, film coated tablets in 500 mg and 875 mg strengths, chewable tablets in 125 mg and 250 mg strengths, and oral suspensions in 125 mg/5 mL, 200 mg/5 mL, 250 mg/5 mL, and 400 mg/5 mL concentrations. In adults, the usual dose ranges from 500 mg every 12 hours or 250 mg every 8 hours for mild to moderate infections, up to 875 mg every 12 hours or 500 mg every 8 hours for severe infections. For lower respiratory tract infections, the label lists 875 mg every 12 hours or 500 mg every 8 hours.

In paediatric patients weighing less than 40 kg and aged 3 months or older, the label lists 20 to 45 mg/kg/day divided every 8 to 12 hours, depending on infection severity. For H. pylori infection in adults, triple therapy consists of 1 gram amoxicillin, 500 mg clarithromycin, and 30 mg lansoprazole, all given twice daily for 14 days. Dual therapy consists of 1 gram amoxicillin and 30 mg lansoprazole, each given three times daily for 14 days.

If a dose of amoxicillin is missed, it should generally be taken as soon as remembered. However, if it is nearly time for the next scheduled dose, the missed dose should be skipped and the regular dosing schedule resumed. Doses should not be doubled to make up for a missed dose.

Because amoxicillin is typically dosed every 8 or 12 hours to maintain effective levels against bacteria, maintaining a consistent schedule is important for treatment success. Patients should contact their pharmacist or doctor if they have questions about missed doses or if multiple doses have been missed.

Amoxicillin is classified as Pregnancy Category B. Reproduction studies in mice and rats at doses up to 2000 mg/kg showed no evidence of harm to the foetus. However, there are no adequate and well-controlled studies in pregnant women.

Because animal reproduction studies are not always predictive of human response, amoxicillin should be used during pregnancy only if clearly needed. Penicillins are excreted in human milk, and amoxicillin use by nursing mothers may lead to sensitisation of infants. Caution should be exercised when amoxicillin is administered to a nursing woman.

The label directs that capsules, tablets, and unreconstituted powder for oral suspension should be stored at 20° to 25°C. Once the powder for oral suspension has been reconstituted with water, the suspension should be kept in a tightly closed bottle and any unused portion must be discarded after 14 days. Refrigeration of reconstituted suspension is preferable but not required to maintain quality.