ampicillin
Apo-Ampi ◆, Novo-Ampicillin ◆, Omnipen, Penbritin ◆

ampicillin sodium
Ampicin ◆, Omnipen-N, Penbritin ◆

ampicillin trihydrate
Principen, Totacillin

Pharmacologic classification: aminopenicillin
Therapeutic classification: antibiotic
Pregnancy risk category B


Available forms
Available by prescription only
Capsules: 250 mg, 500 mg
Infusion: 500 mg, 1 g, 2 g
Parenteral: 125 mg, 250 mg, 500 mg, 1 g, 2 g
Suspension: 125 mg/5 ml, 250 mg/5 ml

Indications and dosages
 Systemic infections, acute and chronic urinary tract infections caused by susceptible organisms. Adults: 250 to 500 mg P.O. q 6 hours.
Children who weigh less than 40 kg (88 lb): 25 to 100 mg/kg P.O. daily, divided into doses given q 6 hours; or 100 to 200 mg/kg I.V. daily for 3 days and then I.M., divided into doses given q 6 to 8 hours.
 Meningitis. Adults: 8 to 14 g I.V. or 150 to 200 mg/kg daily divided q 3 to 4 hours for 3 days; then may give I.M. if desired.
Children ages 2 months to 12 years: 200 to 400 mg/kg I.V. daily in divided doses q 4 to 6 hours. May be given along with chloramphenicol, pending culture results.
Neonates older than 1 week: 50 mg/kg I.V. q 8 hours (weight under 2 kg) or q 6 hours (weight over 2 kg).
Neonates younger than 1 week: 50 to 75 mg/kg I.V. q 12 hours (weight under 2 kg [4.4 lb]) or q 8 hours (weight over 2 kg).
 Neonatal group B streptococcal meningitis. Neonates age 7 days and older: 300 mg/kg/ daily I.V. given in 4 to 6 divided doses.
Neonates age 7 days and younger: 200 mg/kg daily I.V. given in three divided doses.
 Uncomplicated gonorrhea. Adults: 3.5 g P.O. with 1 g probenecid given as a single dose.
≡ Dosage adjustment. For patients with severe renal impairment (creatinine clearance 10 ml/ minute or less), increase dosing interval to q 12 hours.
 Prophylaxis for bacterial endocarditis before dental or minor respiratory procedures. Adults: 2 g (I.V. or I.M.) 30 minutes before procedure.
Children: 50 mg/kg I.V. or I.M. 30 minutes before procedure.
 Treatment of enterococcal endocarditis. Adults: 12 g daily by continuous I.V. infusion or in six equally divided doses with gentamicinfor 4 to 6 weeks.
 Prophylaxis of neonatal group B streptococcus infections ◇. Adults: 2 g I.V. given to the mother at least 4 hours before delivery, and then 1 to 2 g I.V. q 4 to 6 hours until delivery.

Pharmacodynamics
Antibiotic action: Ampicillin is bactericidal; it adheres to bacterial penicillin-binding proteins, inhibiting bacterial cell wall synthesis. Spectrum of activity includes non-penicillinase-producing gram-positive bacteria. It’s also effective against many gram-negative organisms, including Neisseria gonorrhoeae, Neisseria meningitidis, Haemophilus influenzae, Escherichia coli, Proteus mirabilis, Salmonella species, and Shigella species. Ampicillin should be used in gram-negative systemic infections only when organism sensitivity is known.

Pharmacokinetics
Absorption: About 42% of ampicillin is absorbed after an oral dose.
Distribution: Distributed into pleural, peritoneal, and synovial fluids, lungs, prostate, liver, and gallbladder; it also penetrates middle ear effusions, maxillary sinus and bronchial secretions, tonsils, and sputum. Readily crosses the placental barrier; minimally protein-bound (15% to 25%).
Metabolism: Only partially metabolized.
Excretion: Excreted in urine by renal tubular secretion and glomerular filtration. It also appears in breast milk. Elimination half-life is about 1 to 11/2 hours; in patients with extensive renal impairment, half-life is extended to 10 to 24 hours.

Route Onset Peak Duration
P.O. Unknown 2 hr 6-8 hr
I.V. Immediate Immediate Unknown
I.M. Unknown 1 hr Unknown


Contraindications and precautions
Contraindicated in patients hypersensitive to drug or other penicillins. Use cautiously in patients with mononucleosis.

Interactions
Drug-drug. Allopurinol: Appears to increase occurrence of rash from both drugs. Monitor patient closely.
Aminoglycoside antibiotics: Cause synergistic bactericidal effect against some strains of enterococci and group B streptococci. However, drugs are physically and chemically incompatible and are inactivated if mixed or given together. Don’t mix together.
Hormonal contraceptives: May decrease effects of hormonal contraceptives. Advise using alternative barrier method.
Methotrexate: Large doses of penicillins may interfere with renal tubular secretion of methotrexate, delaying elimination and elevating serum methotrexate level. Monitor patient for methotrexate toxicity.
Probenecid: Inhibits renal tubular secretion of ampicillin, raising its serum level. Avoid use together.
Drug-herb. Khat: May decrease antimicrobial effect of certain penicillins. Discourage khat chewing, or tell patient to take amoxicillin 2 hours after chewing khat.

Adverse reactions
CNS: lethargy, hallucinations, seizures, anxiety, confusion, agitation, depression, dizziness, fatigue.
CV: thrombophlebitis, vein irritation.
GI: nausea, vomiting, diarrhea, glossitis, stomatitis, gastritis, abdominal pain, enterocolitis, pseudomembranous colitis, black "hairy" tongue.
GU: interstitial nephritis, nephropathy, vaginitis.
Hematologic: anemia, thrombocytopenia,thrombocytopenic purpura, eosinophilia, leukopenia, hemolytic anemia, agranulocytosis.
Other: hypersensitivity reactions (erythematous maculopapular rash, urticaria, anaphylaxis), overgrowth of nonsusceptible organisms, pain at injection site.

Effects on lab test results
• May increase eosinophil count. May decrease hemoglobin and platelet, WBC, and granulocyte counts.

Overdose and treatment
Signs of overdose include neuromuscular sensitivity and seizures.
 After recent ingestion (within 4 hours), empty the stomach by induced emesis or gastric lavage; follow with activated charcoal to reduce absorption. Drug can be removed by hemodialysis.

Special considerations
• Ampicillin alters results of urine glucose tests that use cupric sulfate (Benedict’s reagent or Clinitest). Urine glucose determinations should be done with glucose oxidase methods (Chemstrip uG, Diastix, or glucose enzymatic test strip).
• Consider the recommendations relevant to all penicillins.
• Obtain patient’s allergy history before dispensing drug.
• Administer I.M. or I.V. only when patient is too ill to take oral drug.
• Monitor renal, hepatic, and hematologic systems during prolonged therapy.
Pregnant patients
• Safe use during pregnancy hasn’t been established, but drug has been used to treat urinary tract infections in pregnant women without affecting the fetus.
Breast-feeding patients
• Use cautiously. Ampicillin is distributed readily into breast milk; safety in breast-feeding women hasn’t been established.
Geriatric patients
• Because of diminished renal tubular secretion in geriatric patients, half-life of drug may be prolonged.

Patient education
• Advise patient to report diarrhea promptly.
• Instruct patient to complete all of the prescribed drug.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use