Ampicillin for Injection: Uses, Dosage and Side Effects

Ampicillin for Injection is a penicillin-class antibiotic indicated for the treatment of serious bacterial infections caused by susceptible organisms. Depending on the organism and susceptibility, indications may include respiratory tract infections, urinary tract infections, gastrointestinal infections, septicemia, meningitis, and infections caused by susceptible strains of Enterococcus, Listeria monocytogenes, and certain streptococci. Treatment should be guided by culture and susceptibility results whenever appropriate. Ampicillin is not effective against viral infections.

Common adverse reactions include rash, diarrhea, nausea, vomiting, and injection-site pain or inflammation. Other possible reactions include phlebitis following intravenous administration and hypersensitivity reactions. Serious adverse effects may include anaphylaxis, severe cutaneous reactions, antibiotic-associated colitis caused by Clostridioides difficile, blood cell abnormalities, liver enzyme elevations, and seizures, particularly with high doses or impaired renal function.

Obtain appropriate cultures before starting treatment when feasible. Adjust dosage in patients with renal impairment. Monitor for allergic reactions, severe or persistent diarrhea, superinfection, and changes in blood counts or liver function during prolonged therapy. Patients with infectious mononucleosis have an increased risk of developing an ampicillin-associated rash. Use the correct diluent, concentration, route, and administration rate according to the specific product instructions. This medicine should be prepared and administered by qualified healthcare professionals.

Dosage depends on the type and severity of infection, pathogen susceptibility, age, body weight, renal function, and clinical response. Adult regimens for susceptible infections commonly range from 1–2 g intravenously every 4–6 hours, although the appropriate regimen varies substantially by indication. Serious infections such as meningitis may require higher, indication-specific doses under specialist supervision. Pediatric dosing is calculated according to body weight and the infection being treated. Adjust dosage or dosing intervals in renal impairment. Reconstitute and administer the product according to the manufacturer's prescribing information. Do not use a fixed regimen without a clinician's assessment.

Probenecid may reduce renal excretion and increase ampicillin concentrations. Allopurinol may increase the risk of skin rash. Ampicillin may alter the anticoagulant response to warfarin, requiring closer monitoring. It may reduce methotrexate clearance and increase the risk of toxicity. Concurrent use with other antibiotics should be determined by the infection, susceptibility results, and clinical treatment plan. Review all prescription medicines, over-the-counter products, and supplements before treatment.