Ampicillin Medication Guide

Composition and Formulation

Ampicillin is a broad-spectrum penicillin-type beta-lactam antibiotic. It is derived from 6-aminopenicillanic acid. It is available in various formulations including capsules, tablets, and powder for oral suspension as well as injectable solutions.

Mechanism of Action

Ampicillin works by inhibiting bacterial cell wall synthesis. It binds to penicillin-binding proteins inside the bacterial cell wall, leading to cell lysis and death. It is effective against a wide range of gram-positive and gram-negative bacteria.

Indications for Use

Ampicillin is indicated for the treatment of various bacterial infections such as respiratory tract infections, urinary tract infections, gastrointestinal infections, and meningitis. It is also used for bacterial endocarditis and septicemia.

Pharmacokinetics Information

Ampicillin demonstrates rapid absorption when administered orally, but its bioavailability is reduced by the presence of food. It is widely distributed in body tissues and fluids, including cerebrospinal fluid when the meninges are inflamed. It is primarily excreted unchanged in the urine.

Dosage and Administration

The dosage of ampicillin varies depending on the type and severity of infection, as well as patient age, weight, and renal function. For adults, the common oral dosage ranges from 250 mg to 500 mg every 6 hours. For children, it is generally dosed based on body weight.

Drug Interactions

Ampicillin may interact with other medications such as allopurinol, oral anticoagulants, and other antibiotics. It may reduce the effectiveness of oral contraceptives. Probenecid inhibits renal tubular secretion of ampicillin, leading to increased concentrations and prolonged action.

Side Effects Profile

Common side effects include diarrhea, nausea, vomiting, and rash. Serious but rare side effects include anaphylaxis, Stevens-Johnson syndrome, and pseudomembranous colitis. Long-term usage can lead to superinfections with resistant organisms.

Special Populations Consideration

Ampicillin should be used cautiously in patients with renal impairment, as decreased renal function can lead to accumulation of the drug. Dosage adjustments may be necessary. For pregnant women, ampicillin falls under Category B as animal studies have not shown harm to the fetus, but no adequate studies in pregnant women exist.

Laboratory Test Interferences

Ampicillin can cause false-positive results in certain types of glucose tests in urine. It may also affect the results of the Coombs’ test and serum protein determinations.

Storage and Stability

Ampicillin capsules and tablets should be stored at room temperature, away from moisture and heat. The powder for oral suspension should be stored at room temperature or refrigerated and used within a specified time after reconstitution. Injectable solutions should be stored according to the manufacturer’s guidelines.

Contraindications and Precautions

Ampicillin is contraindicated in patients with a history of allergic reactions to beta-lactam antibiotics. Caution should be exercised in patients with a history of gastrointestinal diseases, particularly colitis. Regular monitoring for signs of superinfection is necessary when used for prolonged periods.

Patient Counseling Information

Patients should be informed to take ampicillin at evenly spaced intervals to maintain effective drug levels. They should complete the full prescribed course even if symptoms resolve early. Patients should report any signs of allergic reactions or severe side effects to a healthcare professional immediately.