Ampicillin

Indications

Ampicillin treats infections caused by bacteria that are sensitive to it, including chest infections (bronchitis, pneumonia), ear, sinus and throat infections, urinary tract infections, some gut infections and some infections of the skin and soft tissue. The injection is used in hospital for serious infections such as meningitis, blood infection (septicaemia) and infections around childbirth. Many bacteria are now resistant, so a doctor should decide whether it is the right antibiotic.

How It Works

Ampicillin is a penicillin antibiotic. It stops bacteria building their cell walls, so they burst and die. It does not work against viral infections such as colds or flu.

Dosage and Administration

• Adults, capsules: usually 500 mg every 6 hours; the doctor may prescribe 250 mg to 1 g every 6 hours depending on the infection.
• Children, suspension or paediatric drops: dose depends on age and weight, as prescribed.
• Injection: given by a doctor or nurse.

Take on an empty stomach, 30 minutes to 1 hour before food, spacing doses evenly through the day. Complete the full course even if you feel better. Shake the suspension well and use the measuring spoon or dropper provided.

Interactions

Allopurinol increases the chance of skin rash. Ampicillin can raise Methotrexate levels and increase the effect of Warfarin. Probenecid raises ampicillin levels. Tetracyclines, Chloramphenicol and Erythromycin may reduce its effect. It can make the oral typhoid vaccine less effective. If you have vomiting or diarrhoea while taking contraceptive pills, use extra protection.

Contraindications

• Allergy to ampicillin or any penicillin
• A previous serious allergic reaction to cephalosporins or other beta-lactam antibiotics

Side Effects

Common: diarrhoea, nausea, vomiting, skin rash and thrush (yeast infection) of the mouth or vagina. A rash is very common in people with glandular fever (infectious mononucleosis).

Get urgent medical help for swelling of the face, lips, tongue or throat, difficulty breathing, hives or fainting (a severe allergic reaction); a severe skin reaction with blisters or peeling; severe watery or bloody diarrhoea, even weeks after the course; yellow skin or eyes; or fits.

Pregnancy and Lactation

Ampicillin is generally considered safe in pregnancy when prescribed by a doctor. Small amounts pass into breast milk; breastfeeding can usually continue, but watch the baby for diarrhoea, thrush or rash and tell the doctor.

Precautions and Warnings

• Tell your doctor about any previous allergic reactions to antibiotics.
• Tell your doctor if you have glandular fever, kidney disease (the dose may need lowering) or a history of severe allergies or asthma.
• Long courses may need blood, kidney and liver tests.
• The suspension may contain sugar; people with diabetes should take this into account.

Overdose

Too much may cause nausea, vomiting and diarrhoea. Very high doses, especially in people with kidney failure, can cause fits. Seek medical help.

Therapeutic Class

Penicillin antibiotic (aminopenicillin).

Storage

Store capsules and dry powder below 30°C in a dry place, away from light and out of the reach of children. After mixing, keep the suspension or drops as stated on the label (usually in a refrigerator at 2 to 8°C) and use within 7 days; throw away any left over.