Adult: 0.25-1 g 6 hrly. Child: <10 yr Half of adult routine dosage.
Oral Paratyphoid fever, Typhoid fever
Adult: 1-2 g 6 hrly for 2 wk in acute infections, and 4-12 wk in carriers.
Oral Uncomplicated gonorrhoea
Adult: 2 g w/ 1 g of probenecid as single dose, recommended to be repeated in female patients.
Oral Urinary tract infections
Adult: 500 mg 8 hrly.
Parenteral Susceptible infections
Adult: 500 mg 6 hrly, via IM or slow IV inj over 3-5 min or by infusion. Child: <10 yr Half of adult routine dosage.
Parenteral Septicaemia
Adult: 150-200 mg/kg daily. Initiate w/ IV admin for at least 3 days, then continue w/ IM inj 3-4 hrly. Continue treatment for at least 48-72 hr after the patient has become asymptomatic or when there is evidence of bacterial eradication. Recommended treatment duration for infections caused by group-A β-haemolytic streptococci: At least 10-days, to prevent occurrence of acute rheumatic fever or acute glomerulonephritis. Child: Same as adult dose.
Renal Impairment
Patients undergoing haemodialysis should receive an additional dose after the session.
CrCl
Dosage
<10
Dose reduction or increase in dose interval.
Administration
Should be taken on an empty stomach. Take 1 hr before or 2 hr after meals.
Reconstitution
Intramuscular:
Add 1.5 mL water for inj to 500 mg vial contents. Intravenous:
Dissolve 500 mg in 10 mL water for inj. May be added to infusion fluids or injected, suitably diluted into the drip tube. Intra-articular:
Dissolve 500 mg in up to 5 mL of water for inj or sterile procaine HCl 0.5% soln. Intraperitoneal:
Dissolve 500 mg in up to 10 mL water for inj. Intrapleural:
Dissolve 500 mg in 5-10 mL water for inj.
Monitor renal, hepatic, and haematologic function periodically; observe signs and symptoms of anaphylaxis during 1st dose.
Overdosage
Symptoms: Nausea, vomiting and diarrhoea. Management: Symptomatic and supportive treatment. May be removed from the circulation by haemodialysis.
Drug 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.
Food Interaction
Food decreases rate and extent of absorption.
Lab Interference
May interfere w/ diagnostic tests for urinary glucose using copper sulfate, direct antiglobulin (Coombs' test), tests for urinary or serum proteins and tests using bacteria (e.g. Guthrie test for phenylketonuria using Bacillus subtilis).
Action
Description: Ampicillin inhibits bacterial cell wall synthesis by binding to 1 or more of the penicillin-binding proteins (PBPs) which in turn inhibit the final transpeptidation step of peptidoglycan synthesis in bacterial cell walls. Bacteria eventually lyse due to ongoing activity of cell wall autolytic enzymes (autolysins and murein hydrolases) while cell wall assembly is arrested. Pharmacokinetics: Absorption: Moderately well absorbed from the GI tract (50%). Food may reduce rate and extent of absorption. Time to peak plasma concentration: Approx 1-2 hr. Distribution: Widely distributed. Crosses the placenta and enters breast milk (small amounts). Plasma protein binding: Approx 20%. Metabolism: Metabolised to some extent to penicilloic acid. Excretion: Via urine as unchanged drug (oral: approx 20-40%; parenteral: approx 60-80%) w/in 6 hr and faeces (small amounts). Plasma half-life: Approx 1-1.5 hr.
Chemical Structure
Ampicillin Source: National Center for Biotechnology Information. PubChem Database. Ampicillin, CID=6249, https://pubchem.ncbi.nlm.nih.gov/compound/Ampicillin (accessed on Jan. 20, 2020)
Storage
Store between 20-25°C. Reconstituted oral susp: Store between 2-8°C (discard after 14 days).
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