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MEDICINE MONOGRAPH CODE: [8.15] ID: TIP-MED-000143

Ampicillin, Cloxacillin & Benzathine Penicillin G

Active Ingredient / Scientific Identity: Ampicillin, Cloxacillin & Benzathine Penicillin G • Class: Aminopenicillin, Isoxazolyl Penicillin & Long-Acting Depot Penicillin (Schedule H | NLEM 2022)

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THE INDIAN PHARMACIST — Educational Reference Sheet
Profile: Ampicillin, Cloxacillin & Benzathine Penicillin G ([8.15] | ID: TIP-MED-000143) • Last Reviewed: 2026-11-10
Source URL: https://theindianpharmacist.com/medicine/8-15-ampicillin-cloxacillin-benzathine-penicillin-g/
Generic / Entity NameAmpicillin, Cloxacillin & Benzathine Penicillin G ([8.15])
Verified Indian Brands / RefGeneric Compendial Entry (No Commercial Brand Claimed)
Pharmacological ClassAminopenicillin, Isoxazolyl Penicillin & Long-Acting Depot Penicillin (Schedule H | NLEM 2
Available Dosage FormsOral Capsules: 250 mg, 500 mg; Dry Syrup: 125 mg/5mL. Penidure LA Vials: 6 Lakh IU, 1.2 MU, 2.4 MU for DEEP IM
Regulatory ClassificationSchedule H Prescription Drug (To be sold by retail on the prescription of a Registere
Key Warning & Review DateRenal: Extend Ampicillin interval to q8–12h if eGFR <30 mL/min. Hepatic: Monitor LFTs on high-dose Cloxacillin
Reviewed: 2026-11-10
Safety Matrix:⚖️ Legal Status: Schedule H Prescription Drug (To be sold by retail o✔️ Standard Clinical Dispensing Precautions

1. Clinical & Scientific Overview

Ampicillin, Cloxacillin & Benzathine Penicillin G (TIP-MED-000143, Reference Code [8.15]) is classified under Antimicrobials — Antibacterial & Antibiotic Agents (Ch 08) as a Aminopenicillin, Isoxazolyl Penicillin & Long-Acting Depot Penicillin (Schedule H | NLEM 2022). Within the Indian regulatory and compendial framework, it is governed under Schedule H Prescription Drug (To be sold by retail on the prescription of a Registered Medical Practitioner only — Drugs Rules 1945).

Verified Indian Market Examples / Compendial Status:
Representative Indian Market Examples (Edition 2.7 Ch 08 [8.15], p. 100): Ampicillin: Roscillin (Ranbaxy). Cloxacillin: Klox (Lyka), Bioclox; FDC: Ampoxin. Benzathine Penicillin G: Penidure LA 6 / LA 12 / LA 24 (Pfizer) — Strengths & Dosage Forms: Oral Capsules: 250 mg, 500 mg; Dry Syrup: 125 mg/5mL. Penidure LA Vials: 6 Lakh IU, 1.2 MU, 2.4 MU for DEEP IM ONLY
Representative Indian Market Examples (Edition 2.7 Ch 08 [8.15], p. 100): Ampicillin: Roscillin (Ranbaxy). Cloxacillin: Klox (Lyka), Bioclox; FDC: Ampoxin. Benzathine Penicillin G: Penidure LA 6 / LA 12 / LA 24 (Pfizer) — Strengths & Dosage Forms: Oral Capsules: 250 mg, 500 mg; Dry Syrup: 125 mg/5mL. Penidure LA Vials: 6 Lakh IU, 1.2 MU, 2.4 MU for DEEP IM ONLY
Dosage Forms & Available Strengths:
Oral Capsules: 250 mg, 500 mg; Dry Syrup: 125 mg/5mL. Penidure LA Vials: 6 Lakh IU, 1.2 MU, 2.4 MU for DEEP IM ONLY
Routes: Oral / Parenteral / Topical as specified by formulation

3. Mechanism of Action & Pharmacodynamics

Aminopenicillin, Isoxazolyl Penicillin & Long-Acting Depot Penicillin (Schedule H | NLEM 2022) acting on target receptor/enzyme pathways in Antimicrobials — Antibacterial & Antibiotic Agents (Ch 08): clinical efficacy is mediated via Aminopenicillin, Isoxazolyl Penicillin & Long-Acting Depot Penicillin (Schedule H | NLEM 2022) for Cloxacillin: MSSA skin/soft-tissue infections, cellulitis, impetigo, mastitis. Ampicillin: Listeria/Enterococcal infections. Benzathine Penicillin G: Acute rheumatic fever secondary prophylaxis (q21–28d IM) & syphilis.

4. Therapeutic Indications & Evidence-Supported Uses

  • Cloxacillin: MSSA skin/soft-tissue infections, cellulitis, impetigo, mastitis
  • Ampicillin: Listeria/Enterococcal infections
  • Benzathine Penicillin G: Acute rheumatic fever secondary prophylaxis (q21–28d IM) & syphilis

🇮🇳 Jurisdiction & Indication Note: Indications and schedules reflect Indian compendial and regulatory records (CDSCO / Indian Pharmacopoeia & NFI / NLEM 2022). Where international reference labels (US FDA DailyMed / NCBI StatPearls) are cited for pharmacokinetic or mechanistic parameters, international approvals do not automatically imply CDSCO approval in India.

5. Educational Dosage Context, Formulations & Administration

Educational Dosing & Regimen Summary: Cloxacillin / Ampicillin: 500 mg PO QID (q6h). Benzathine Penicillin G: Rheumatic Fever Prophylaxis: 1.2 MU (6 Lakh IU if Wt <27 kg) DEEP IM every 3–4 weeks; Early Syphilis: 2.4 MU DEEP IM single dose

Administration & Meal Timing: Take oral Cloxacillin and Ampicillin on an EMPTY STOMACH (1h before or 2h after meals — food cuts Cloxacillin absorption by 50%!). Penidure LA is for DEEP IM buttock injection ONLY! | Every 6 Hours (QID, 1h pre-meal) for Oral; Every 21–28 Days IM for Penidure LA

6. Pharmacokinetics, Metabolism & Renal/Hepatic Adjustment

Absorption & Disposition:
Absorption, distribution, metabolism, and excretion follow class pharmacokinetic profile; verify patient renal/hepatic function.
Metabolism & Biotransformation:
Renal: Extend Ampicillin interval to q8–12h if eGFR <30 mL/min. Hepatic: Monitor LFTs on high-dose Cloxacillin
Elimination & Renal Adjustment:
Renal: Extend Ampicillin interval to q8–12h if eGFR <30 mL/min. Hepatic: Monitor LFTs on high-dose Cloxacillin
Hepatic Impairment Considerations:
Renal: Extend Ampicillin interval to q8–12h if eGFR <30 mL/min. Hepatic: Monitor LFTs on high-dose Cloxacillin

7. Contraindications, Precautions & High-Risk Warnings

Contraindications & Red-Flag Precautions:
  • CONTRAINDICATIONS: Any history of Penicillin or Beta-Lactam anaphylaxis! NEVER inject Benzathine Penicillin G intravenously (IV injection causes instant cardiopulmonary arrest!). Keep Adrenaline 1:1000 IM ready

Key Clinical Precautions: Renal: Extend Ampicillin interval to q8–12h if eGFR <30 mL/min. Hepatic: Monitor LFTs on high-dose Cloxacillin

8. Adverse Effects Profile

Common & Mechanism-Related Adverse Effects:
  • Diarrhoea, nausea, maculopapular rash (especially Ampicillin in EBV mononucleosis!), pain at IM injection site
  • IgE-mediated anaphylactic shock, angioedema, SJS/TEN, C. difficile colitis, Hoigne syndrome, Nicolau syndrome
Serious / Dose-Limiting Adverse Effects:
  • Monitor for severe hypersensitivity, organ toxicity, or dose-limiting adverse events.

9. Major Drug–Drug, Drug–Food & Drug–Herb Interactions

  • Probenecid blocks renal tubular secretion of penicillins; Penicillins reduce renal clearance of Methotrexate (toxicity!); Allopurinol + Ampicillin increases skin rash incidence

10. Clinical Monitoring, Patient Counselling & Storage

Clinical & Laboratory Monitoring: Monitor clinical response, baseline renal/hepatic parameters, and relevant serum biomarkers.

Pharmacist Patient Counselling Points:

  • Patient Counselling Checklist: Take oral Klox/Roscillin 1 full hour before meals on an empty stomach; always inform every doctor and pharmacist if you ever had a rash or breathing difficulty after Penicillin
  • Meal & Clock Timing Instruction: Take oral Cloxacillin and Ampicillin on an EMPTY STOMACH (1h before or 2h after meals — food cuts Cloxacillin absorption by 50%!). Penidure LA is for DEEP IM buttock injection ONLY! (Every 6 Hours (QID, 1h pre-meal) for Oral; Every 21–28 Days IM for Penidure LA)
  • Missed Dose Protocol: Take as soon as remembered to maintain T>MIC; never skip rheumatic heart disease monthly IM injections
  • Geriatric Dispensing Pearl: Adjust Ampicillin for Cockcroft–Gault CrCl in older adults

Storage, Stability & Dispensing Safeguards: Store below 25°C–30°C in original moisture- and light-resistant packaging out of reach of children. Available forms: Oral Capsules: 250 mg, 500 mg; Dry Syrup: 125 mg/5mL. Penidure LA Vials: 6 Lakh IU, 1.2 MU, 2.4 MU for DEEP IM ONLY

11. Visual Pharmacology & Mechanism Diagram (svg-v339-01-adme-12-step-journey)

THE 12-STEP ORAL DRUG JOURNEY THROUGH THE HUMAN BODY (LADME) Note: IV bolus enters Step 6 directly (F = 100%); Sublingual & Transdermal routes bypass Step 4–5 Portal First-Pass Metabolism 1. Oral Administration • Tablet / Capsule swallowed • Gastric emptying to duodenum pH 1.5–3.5 (Stomach) 2. Disintegration & Dissolution • Tablet breaks into granules • API dissolves in GI fluid Noyes-Whitney Dissolution Rate 3. GI Epithelial Absorption • Crosses intestinal villi • Passive / Active / P-gp efflux Small Intestine (Large Surface Area) 4. Portal Circulation • Mesenteric veins → Portal vein • Delivers blood to liver sinusoids Pre-systemic Venous Conduit 5. First-Pass Metabolism • Gut & hepatic CYP450 extraction • High: GTN, Propranolol, Morphine Determines Bioavailability (F = f_a × (1-E_H)) 6. Systemic Circulation • Hepatic vein → IVC → Heart • Unbound vs Albumin-bound drug Only FREE drug is active 7–8. Tissue Distribution (Vd) • Capillary permeation to organs • Blood-Brain & Placental barriers Vd = Dose / C_0 (L or L/kg) 9. Target Site of Action • Receptors (GPCR, Ion channel) • Enzymes & Carrier Transporters Pharmacodynamic Effect (E_max, EC50) 10. Hepatic Biotransformation • Phase I (CYP450 Oxidation/Hydrolysis) • Phase II (Glucuronidation/Sulfation) Converts lipophilic drug → hydrophilic metabolite 11. Renal & Biliary Elimination • Nephron: Filtration + Secretion − Reabsorption • Biliary excretion & Enterohepatic recycling Total Clearance CL_tot = CL_renal + CL_hepatic 12. Excretion from the Body • Urine (Primary polar metabolite route) • Bile/Faeces, Expired Air, Sweat, Milk Elimination Half-Life t1/2 = (0.693 × Vd) / CL
svg-v339-01-adme-12-step-journey — 8.1 Complete 12-Step Journey of an Orally Administered Drug (ADME): Figure 8.1: The 12-step physiological journey of a typical orally administered solid dosage form through Liberation, Absorption, Distribution, Metabolism, and Excretion (LADME). Note: Parenteral (IV), sublingual, and inhalational routes bypass gastrointestinal absorption and/or hepatic first-pass metabolism.

12. Authoritative References, Regulatory Sources & Editorial Disclaimer

Primary Compendial & Guideline Reference: Indian Pharmacist Desk Reference — Professional Edition 2.7 (2026–27) • Ch 08 [8.15] (p. 100)

Official Verification Portals: Indian Pharmacopoeia Commission (IPC) & National Formulary of India (NFI) • Central Drugs Standard Control Organization (CDSCO) • Ministry of Health & Family Welfare — NLEM 2022 • NCBI Bookshelf / StatPearls Pharmacology Reference • DailyMed (US FDA Official Prescribing Reference)

Last Medically & Pharmaceutically Reviewed: 2026-11-10 • Verification Status: HANDBOOK_SOURCE_CONTENT

Educational & Clinical Disclaimer: This reference profile is published solely for pharmacy education, academic study, and professional clinical reference. It does not substitute for patient-specific clinical judgement, qualified specialist oncology/medical supervision, or official CDSCO/IP prescribing information. Never self-medicate with prescription, Schedule H/H1/X, NDPS, or oncology medicines.

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Educational Reference Notice: This printout from THE INDIAN PHARMACIST (https://theindianpharmacist.com/medicine/8-15-ampicillin-cloxacillin-benzathine-penicillin-g/, Last Reviewed: 2026-11-10) is an educational reference sheet for students and healthcare learners. It is NOT an official prescribing guideline or patient-specific treatment order.