Drug information of ampicillin


Drug group:

Ampicillin is a penicillin antibiotic that fights bacteria. Ampicillin is used to treat or prevent many different types of infections such as bladder infections, pneumonia, gonorrhea, meningitis, or infections of the stomach or intestines.

Mechanism of effect

By binding to specific penicillin-binding proteins (PBPs) located inside the bacterial cell wall, Ampicillin inhibits the third and last stage of bacterial cell wall synthesis. Cell lysis is then mediated by bacterial cell wall autolytic enzymes such as autolysins; it is possible that Ampicillin interferes with an autolysin inhibitor.


Ampicillin is a penicillin beta-lactam antibiotic used in the treatment of bacterial infections caused by susceptible, usually gram-positive, organisms


Ampicillin is excreted largely unchanged in the urine.

Drug indications

bacterial infection


Usual Adult Dose for Bacterial Infection The manufacturer recommends: Parenteral: -Infections of the respiratory tract and soft tissues: 250 to 500 mg IM or IV every 6 hours -Infections of the gastrointestinal and genitourinary tracts (including Neisseria gonorrhoeae infections in females): 500 mg IM or IV every 6 hours -Urethritis in males due to N gonorrhoeae: 500 mg IM or IV every 8 to 12 hours for 2 doses -Bacterial meningitis: 150 to 200 mg/kg/day in equally divided doses every 3 to 4 hours; may start with IV drip therapy and continue with IM injections -Septicemia: 150 to 200 mg/kg/day; start with IV administration for at least 3 days and continue with IM route every 3 to 4 hours Oral: -Genitourinary or gastrointestinal tract infections (other than gonorrhea): 500 mg orally every 6 hours -Gonorrhea: 3.5 g orally as a single dose (plus probenecid 1 g) -Respiratory tract infections: 250 mg orally every 6 hours Usual Pediatric Dose for Bacterial Infection American Academy of Pediatrics (AAP) General Dosing Recommendations for Susceptible Infections: Neonates: 7 days or less, 2000 g or less: 50 mg/kg IM or IV every 12 hours 7 days or less, greater than 2000 g: 50 mg/kg IM or IV every 8 hours 8 to 28 days, 2000 g or less: 50 mg/kg IM or IV every 8 hours 8 to 28 days, greater than 2000 g: 50 mg/kg IM or IV every 6 hours 1 month or older: Mild to moderate infections: Parenteral: 25 to 37.5 mg/kg IM or IV every 6 hours Oral: 12.5 to 25 mg/kg orally every 6 hours Maximum dose: 4 g/day Severe infections: 50 to 100 mg/kg IM or IV every 6 hours Maximum dose: 12 g/day


1-Serious and occasionally fatal hypersensitivity (anaphylactic) reactions have been reported in patients on penicillin therapy. 2- Clostridium difficile associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including Ampicillin for injection, and may range in severity from mild diarrhea to fatal colitis. If CDAD is suspected or confirmed, ongoing antibiotic use not directed against C. difficile may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibiotic treatment of C. difficile, and surgical evaluation should be instituted as clinically indicated.

Points of recommendation

1- Patients should be counseled that antibacterial drugs including Ampicillin should only be used to treat bacterial infections. They do not treat viral infections (e.g., the common cold). 2- the medication should be taken exactly as directed. 3- Sometimes after starting treatment with antibiotics, patients can develop watery and bloody stools (with or without stomach cramps and fever) even as late as 2 or more months after having taken the last dose of the antibiotic. If this occurs, patients should contact their physician as soon as possible.

Pregnancy level


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