Amoxicillin

Amoxicillin is a penicillin-type antibiotic, specifically an aminopenicillin, used to fight bacterial infections. It is taken by mouth, or less often given as a shot into a muscle or as a quick intravenous injection. Common side effects include nausea and a rash, and it can raise the chance of yeast infections; when combined with clavulanic acid, it also increases the risk of diarrhea. People allergic to penicillin should avoid it.

Those with kidney problems may need a lower dose. It appears safe to use during pregnancy and while breastfeeding. Amoxicillin belongs to the beta-lactam family of antibiotics.

It treats a range of infections: middle ear infections, strep throat, pneumonia, skin infections, urinary tract infections, Salmonella infections, Lyme disease, chlamydia, and infections of the mouth and teeth (odontogenic infections). For acute otitis media in children under six months, amoxicillin is standard. In children older than two, it usually offers no benefit, but it may help those under two with bilateral ear infections or ear drainage. Dosing for ear infections was traditionally three times daily, but twice-daily or once-daily dosing works just as well.

Respiratory infections

Most sinusitis is viral, so amoxicillin is ineffective there, and its small benefit is often outweighed by side effects. It is the first-line empirical treatment for uncomplicated bacterial sinusitis in both children and adults when cultures are unavailable. For community-acquired pneumonia in adults, it is the preferred first-line drug, either alone for mild-to-moderate cases or combined with a macrolide; it works as well as co-amoxiclav for hospitalized patients. The World Health Organization recommends it for non-severe pneumonia and for preventing anthrax after inhalation exposure.

H. pylori

For stomach infections with Helicobacter pylori, amoxicillin is part of a multi-drug regimen, typically with a proton-pump inhibitor and a macrolide; other combinations, including one with bismuth subsalicylate, also work. It treats early Lyme disease effectively, with no better or worse outcomes than other oral antibiotics. It is used for odontogenic infections and after tooth extractions, especially in people with weakened immune systems. For skin infections like acne vulgaris, it often works when other antibiotics such as doxycycline or minocycline have failed.

Prevention of bacterial endocarditis

In resource-limited settings, the WHO recommends amoxicillin for infants with pneumonia when hospitalization is not possible, and combined with gentamicin for other severe infections. It is also used to prevent bacterial endocarditis in high-risk people undergoing dental work, to prevent infections in people without spleens or with damaged spleens (such as those with sickle-cell disease), and for anthrax prevention and treatment. The United Kingdom advises against using it for endocarditis prophylaxis, though this recommendation has not changed infection rates.

Because some bacteria produce beta-lactamase enzymes that break down amoxicillin, it is often combined with clavulanic acid (a beta-lactamase inhibitor), a combination called co-amoxiclav. Amoxicillin is a moderate-spectrum, bacteriolytic antibiotic in the aminopenicillin family.