Ampicillin
Indications
Ampicillin is used for:
Bacterial infections, Endocarditis, Typhoid fever, Community-acquired pneumonia, Uncomplicated gonorrhea, Susceptible infections, Bacterial meningitis, Paratyphoid fever, Septicaemia, Intrapartum prophylaxis against group B streptococcal infections
Adult Dose
Adult: PO Susceptible infections 0.25-0.5 g 6 hrly.
Typhoid and paratyphoid fever 1-2 g 6 hrly. Duration: 2 wk (acute infections); 4-12 wk (carriers).
Uncomplicated gonorrhoea W/ probenecid: 2 g as single dose.
IV/IM:
IV Intrapartum prophylaxis against group B streptococcal infections Initial, 2 g, then 1 g 4 hrly until delivery.
Septicaemia 150-200 mg/kg/day. Start with IV admin for 3 days, then IM inj 3-4 hrly. Continue treatment for at least 48-72 hr after patient has become asymptomatic or when there is evidence of bacterial eradication.
IV/IM Susceptible infections 250-500 mg 6 hrly.
Meningitis 2-3 g 4-6 hrly, may start w/ IV admin, then continue w/ IM inj.
Inj Supplement to systemic therapy For intrapleural/intraperitoneal/intra-articular admin: 500 mg/day.
Child Dose
Susceptible infections
Child:
PO: 50–100 mg/kg/day divided q6hr if <20
>20 kg 1–2 g/day divided q6hr
IV/IM:
Child: 50–200 mg/kg/day q6h
300–400 mg/kg/day endocarditis/meningitis q4–6h
Renal Dose
Renal impairment: Patients undergoing haemodialysis should receive an additional dose after the session.
CrCl (ml/min)
<10 Dose reduction or increase in dose interval.
Administration
Should be taken on an empty stomach. Take on an empty stomach 1 hr before or 2 hr after meals.
Reconstitution: IM: Add 1.5 mL water for inj to 500 mg vial contents. IV: Dissolve 500 mg in 10 mL water for inj.
Contra Indications
Hypersensitivity; infectious mononucleosis.
Precautions
Renal failure; patients with lymphatic leukaemia or HIV infections; pregnancy and lactation.
Lactation: Excreted in breast milk, use caution
Pregnancy-Lactation
Interactions
May reduce the efficacy of OC. May alter INR while on warfarin and phenindione. May reduce the efficacy of oral typhoid vaccines. May reduce the excretion of methotrexate. Reduced excretion w/ probenecid and sulfinpyrazone, resulting to increased risk of toxicity. Allopurinol increases ampicillin-induced skin reactions. Reduced absorption w/ chloroquine. Bacteriostatic antibacterials (e.g. erythromycin, chloramphenicol, tetracycline) may interfere w/ the bactericidal action of ampicillin.
Adverse Effects
Side effects of Ampicillin :
GI upset, nausea, vomiting, diarrhoea; blood dyscrasias; urticaria, exfoliative dermatitis, rash; fever, seizures; interstitial nephritis.
Potentially Fatal: Anaphylactic shock; pseudomembranous colitis; neuromuscular hypersensitivity; electrolyte imbalance.
Mechanism of Action
Ampicillin exerts bactericidal action on both gm+ve and gm-ve organisms. Its spectrum includes gm+ve organisms eg, S pneumoniae and other Streptococci, L monocytogenes and gm-ve bacteria eg, M catarrhalis, N gonorrhoea, N meningitidis, E coli, P mirabilis, Salmonella, Shigella, and H influenzae. Ampicillin exerts its action by inhibiting the synthesis of bacterial cell wall.