Novo-Ampicillin , Principen
Ampicin , Penbritin 
Classifications: antibiotic; aminopenicillin;

Pregnancy Category: B


250 mg, 500 mg capsules; 125 mg/5 mL, 250 mg/5 mL oral suspension; 125 mg, 250 mg, 500 mg, 1 gm, 2 gm vials


A broad-spectrum, semisynthetic aminopenicillin that is bactericidal but is inactivated by penicillinase (beta-lactamase). Like other penicillins, ampicillin inhibits the final stage of bacterial cell wall synthesis by binding to specific penicillin-binding proteins (PBPs) located inside the bacterial cell wall. This results in lysis and death of bacteria.

Therapeutic Effect

Effective against gram-positive bacteria as well as some gram negative.


Infections of GU, respiratory, and GI tracts and skin and soft tissues; also gonococcal infections, bacterial meningitis, otitis media, sinusitis, and septicemia and for prophylaxis of bacterial endocarditis. Used parenterally only for moderately severe to severe infections.


Hypersensitivity to penicillin derivatives; infectious mononucleosis.

Cautious Use

History of hypersensitivity to cephalosporins; GI disorders; renal disease or impairment; pregnancy (category B) or lactation.

Route & Dosage

Systemic Infections
Adult: PO/IV/IM 250–500 mg q6h
Child (under 40 kg): PO/IV 25–50 mg/kg/d divided q6–8h
Neonate: IV/IM Up to 7 d and up to 2000 g, 50 mg/kg/d divided q12h; up to 7 d and >2000 g, 75 mg/kg/d divided q8h; >7 d, <1200 g, 50 mg/kg/d divided q12h; >7 d and 1200–2000 g, 75 mg/kg/d divided q8h; >7 d, >2000 g, 100 mg/kg/d divided q6h

Adult/Child: IV 150–200 mg/kg/d divided q3–4h
Neonate: IV/IM Up to 7 d and up to 2000 g, 100 mg/kg/d divided q12h; up to 7 d and >2000 g, 150 mg/kg/d divided q8h; >7 d, <1200 g, 100 mg/kg/d divided 2h; >7 d and 1200–2000 g, 150 mg/kg/d divided q8h; >7 d, >2000 g, 200 mg/kg/d divided q6h

Adult: PO 3.5 g with 1 g probenecid times 1 IV/IM 500 mg q8–12h

Bacterial Endocarditis Prophylaxis
Adult: IV 2 g 30 min before procedure
Child: IV 50 mg/kg 30 min before procedure (max: 2 g)

Group B Strep Prophylaxis
Adult: IV 2 g, then 1 g q4h until delivery

Renal Impairment
Clcr 10–30 mL/min: give q6–12h; <10 mL/min: give q12h
Dialysis: Dose should be given after dialysis


  • Give with a full glass of water on an empty stomach (at least 1 h before or 2 h after meals) for maximum absorption. Food hampers rate and extent of oral absorption.
  • Reconstitute each vial by adding the indicated amount of sterile water for injection or bacteriostatic water for injection (1.2 mL to 125 mg; 1 mL to 250 mg; 1.8 mL to 500 mg; 3.5 mL to 1 g; 6.8 mL to 2 g). All reconstituted vials yield 250 mg/mL except the 125 mg vial which yields 125 mg/mL. Administer within 1 h of preparation.
  • Withdraw the ordered dose and inject deep IM into a large muscle.

Verify correct IV concentration and rate of infusion with physician for administration to neonates, infants, and children.

PREPARE: Direct/Intermittent: ?? Reconstitute as follows with sterile water for injection: add 5 mL to 500 mg or fraction thereof; add 7.4 mL to 1 g; add 14.8 mL to 2 g. Final concentration must be ≤30 mg/mL; may be given direct IV as prepared or further diluted in 50 mL or more of NS, D5W, D5/NS, D5W/0.45NaCl, or RL.??Stability of solution varies with diluent and concentration of solution. Solutions in NS are stable for up to 8 h at room temperature; other solutions should be infused within 2–4 h of preparation. Give direct IV within 1 h of preparation. ??Wear disposable gloves when handling drug repeatedly; contact dermatitis occurs frequently in sensitized individuals. 

ADMINISTER: Direct/Intermittent: ??Infuse 500 mg or less slowly over 3–5 min. Give 1–2 g over at least 15 min.??With solutions of 100 mL or more, set rate according to amount of solution, but no faster than direct IV rate.??Convulsions may be induced by too rapid administration. 

INCOMPATIBILITIES Solution/additive: Do not add to a dextrose-containing solution unless entire dose is given within 1 h of preparation. Aztreonam, cefepime, hydrocortisone, prochlorperazine. Y-site: Amphotericin B, epinephrine, fenoldopam, fluconazole, hydralazine, lansoprazole, midazolam, nicardipine, ondansetron, sargramostim, TPN, verapamil, vinorelbine.

  • Store capsules and unopened vials at 15°–30° C (59°–86° F) unless otherwise directed. Keep oral preparations tightly covered.

Adverse Effects (≥1%)

Body as a Whole: Similar to those for penicillin G. Hypersensitivity (pruritus, urticaria, eosinophilia, hemolytic anemia, interstitial nephritis, anaphylactoid reaction); superinfections. CNS: Convulsive seizures with high doses. GI: Diarrhea, nausea, vomiting, pseudomembranous colitis. Other: Severe pain (following IM); phlebitis (following IV). Skin: Rash.

Diagnostic Test Interference

Elevated CPK levels may result from local skeletal muscle injury following IM injection. Urine glucose: high urine drug concentrations can result in false-positive test results with Clinitest or Benedict's [enzymatic glucose oxidase methods (e.g., Clinistix, Diastix, TesTape) are not affected]. AST may be elevated (significance not known).


Drug: Allopurinol increases incidence of rash. Effectiveness of the aminoglycosides may be impaired in patients with severe end-stage renal disease. Chloramphenicol, erythromycin, and tetracycline may reduce bactericidal effects of ampicillin; this interaction is primarily significant when low doses of ampicillin are used. Ampicillin may interfere with the contraceptive action of oral contraceptives (estrogens). Female patients should be advised to consider nonhormonal contraception while on antibiotics. Food: Food may decrease absorption of ampicillin, so it should be taken 1 h before or 2 h after meals.


Absorption: Oral dose is 50% absorbed. Peak effect: 5 min IV, 1 h IM, 2 h PO. Duration: 6–8 h. Distribution: Most body tissues; high CNS concentrations only with inflamed meninges; crosses the placenta. Metabolism: Minimal hepatic metabolism. Elimination: 90% in urine; excreted into breast milk. Half-Life: 1–1.8 h.

Nursing Implications

Assessment & Drug Effects

  • Determine previous hypersensitivity reactions to penicillins, cephalosporins, and other allergens prior to therapy.
  • Lab tests: Baseline C&S tests prior to initiation of therapy; start drug pending results. Baseline and periodic assessments of renal, hepatic, and hematologic functions, particularly during prolonged or high-dose therapy.
  • Note: Sodium content of drug must be considered in patients on sodium restriction.
  • Inspect skin daily and instruct patient to do the same. The appearance of a rash should be carefully evaluated to differentiate a nonallergenic ampicillin rash from a hypersensitivity reaction. Report rash promptly to physician.
  • Note: Incidence of ampicillin rash is higher in patients with infectious mononucleosis or other viral infections, Salmonella infections, lymphocytic leukemia, or hyperuricemia or in patients taking allopurinol.

Patient & Family Education

  • Note: Ampicillin rash is believed to be nonallergenic and therefore its appearance is not an absolute contraindication to future therapy.
  • Report diarrhea to physician; do not self-medicate. Give a detailed report to the physician regarding onset, duration, character of stools, associated symptoms, temperature and weight loss (if any) to help rule out the possibility of drug-induced, potentially fatal pseudomembranous colitis (see Appendix F).
  • Report S&S of superinfection (onset of black, hairy tongue; oral lesions or soreness; rectal or vaginal itching; vaginal discharge; loose, foul-smelling stools; or unusual odor to urine).
  • Notify physician if no improvement is noted within a few days after therapy is started.
  • Take medication around the clock; continue taking medication until it is all gone (usually 10 d) unless otherwise directed by physician or pharmacist.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

© 2006-2022 Last Updated On: 11/16/2022 (0)
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