Ms general surgery PG Exam viva Metrogell levoflox ciproflox pint pcm pint linezolid pint, augmentin, ceftriaxone,cefotaxime,piptaz,lignocaine,meropenum,cefuroxime vials
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surgical antibiotic prophylaxis
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WHO surgical antibiotic prophylaxis antibiotic stewardship guidelines cephalosporin metronidazole
General Surgery PG Viva: Common Drugs and Vials
For every vial, answer in this order: generic name - class - spectrum/mechanism - surgical indication - adult dose - important adverse effects/contraindications.
Always add: “Dose and duration need renal/hepatic adjustment, culture guidance, and local antibiotic policy.”
Always add: “Dose and duration need renal/hepatic adjustment, culture guidance, and local antibiotic policy.”
| Drug / common brand | Class and mechanism | Common surgical use | Typical adult dose | Key viva points / adverse effects |
|---|---|---|---|---|
| Metrogyl (metronidazole) | Nitroimidazole. Produces free-radical metabolites that damage DNA of anaerobes and protozoa. | Anaerobic cover in intra-abdominal infection, perforation peritonitis, colorectal surgery, amoebic liver abscess. Often combined with ceftriaxone/cefotaxime/ciprofloxacin. | 500 mg IV every 8 hours or orally 400-500 mg every 8 hours. | Metallic taste, nausea, peripheral neuropathy with prolonged use, rarely encephalopathy. Avoid alcohol during therapy and for 48-72 h after because of disulfiram-like reaction. |
| Levofloxacin | Fluoroquinolone. Inhibits DNA gyrase and topoisomerase IV. | UTI, pyelonephritis, biliary/intra-abdominal infection when combined with metronidazole if sensitivity supports it. | 500 mg IV/PO once daily or 750 mg once daily depending on infection. Renal dose adjustment required. | Tendinitis/tendon rupture, QT prolongation, dysglycaemia, peripheral neuropathy, CNS effects, C. difficile. Avoid in pregnancy and generally avoid routine use in children. |
| Ciprofloxacin | Fluoroquinolone, inhibits DNA gyrase/topoisomerase IV. Good Gram-negative activity, including some Pseudomonas. Weak anaerobic cover. | Complicated UTI, some biliary and intra-abdominal infections combined with metronidazole, culture-directed Gram-negative infection. | 400 mg IV every 8-12 h or 500 mg PO every 12 h. Renal adjustment. | Same fluoroquinolone warnings: tendinopathy, QT prolongation, neuropathy, dysglycaemia, CNS effects. Avoid antacids/iron close to oral doses due to reduced absorption. |
| PCM / paracetamol | Non-opioid analgesic and antipyretic. | Mild-moderate postoperative pain and fever, as part of multimodal analgesia. | 1 g IV/PO every 6-8 h. Maximum usually 4 g/day in healthy adults, lower maximum in low body weight, malnutrition, chronic alcohol use, or liver disease. | Main danger is hepatotoxicity in overdose. Antidote: N-acetylcysteine. Check all combination medicines to prevent accidental excess daily dose. |
| Linezolid | Oxazolidinone. Blocks formation of the 70S initiation complex. Active against resistant Gram-positive organisms including MRSA and VRE. | Culture-directed MRSA/VRE wound, soft tissue, bone/joint, or hospital-acquired infection. Not routine empiric therapy for abdominal sepsis. | 600 mg IV/PO every 12 h. Excellent oral bioavailability. | Thrombocytopenia and myelosuppression, especially beyond 1-2 weeks; peripheral/optic neuropathy with prolonged therapy; lactic acidosis. MAOI effect: risk of serotonin syndrome with SSRIs and serotonergic agents. |
| Augmentin (amoxicillin-clavulanate) | Aminopenicillin plus beta-lactamase inhibitor. | Community-acquired skin/soft-tissue, bite wounds, biliary infection, selected intra-abdominal infections, oral step-down therapy. | IV: 1.2 g every 8 h. Oral: commonly 625 mg every 8 h or 875/125 mg every 12 h, according to formulation. | Allergy/anaphylaxis, diarrhoea, C. difficile, cholestatic hepatitis. Avoid with prior serious beta-lactam reaction; adjust in renal impairment. |
| Ceftriaxone | Third-generation cephalosporin, bactericidal cell-wall inhibitor. Good Gram-negative and streptococcal cover, no reliable anaerobic or enterococcal cover. | Sepsis of community origin, biliary infection, complicated UTI, intra-abdominal infection with metronidazole. | 1-2 g IV once daily, sometimes 2 g every 12 h for specific severe infections. | Hypersensitivity, diarrhoea, biliary sludge/pseudolithiasis. Avoid mixing with calcium-containing IV solutions in neonates. Usually does not need renal adjustment alone. |
| Cefotaxime | Third-generation cephalosporin. | Similar to ceftriaxone: severe community-acquired infection, UTI, biliary/intra-abdominal infection with metronidazole. | 1-2 g IV every 8 h. | Beta-lactam allergy, diarrhoea, C. difficile. Requires renal dose adjustment. Shorter half-life than ceftriaxone. |
| Piptaz (piperacillin-tazobactam) | Antipseudomonal ureidopenicillin plus beta-lactamase inhibitor. Broad Gram-positive, Gram-negative including Pseudomonas, and anaerobic activity. | Severe intra-abdominal sepsis, perforation peritonitis, complicated biliary infection, diabetic foot, hospital-acquired infection. | 4.5 g IV every 6-8 h, usually infused over 30 min; extended infusion is used in some protocols. Renal adjustment. | Allergy, diarrhoea, thrombocytopenia, raised liver enzymes, sodium load. Broad-spectrum agent: de-escalate once culture results are available. |
| Lignocaine / lidocaine | Amide local anaesthetic. Blocks voltage-gated sodium channels. Also class Ib antiarrhythmic. | Local infiltration, field block, wound infiltration, nerve blocks, suturing, abscess drainage. | Local infiltration commonly 1% or 2%. Maximum plain lignocaine: 4.5 mg/kg, up to 300 mg. With adrenaline: 7 mg/kg, up to 500 mg. | Toxicity: circumoral numbness, tinnitus, metallic taste, agitation/seizures, then hypotension, arrhythmia and cardiac arrest. Treat local anaesthetic systemic toxicity with airway support, seizure control and 20% lipid emulsion. Avoid adrenaline-containing solution in end-arterial areas depending on institutional policy and vascular status. |
| Meropenem | Carbapenem beta-lactam. Very broad spectrum including anaerobes and many ESBL-producing Gram-negative bacilli; active against Pseudomonas. Not active against MRSA, VRE, atypicals. | Severe sepsis, healthcare-associated/perforation-related intra-abdominal sepsis, ESBL infection, culture-directed resistant Gram-negative infection. | 1 g IV every 8 h. Higher doses may be used in selected infections. Renal adjustment essential. | Seizures are possible, especially in renal failure, though less than imipenem; allergy, diarrhoea, C. difficile. Reserve for resistant organisms and severe illness. |
| Cefuroxime | Second-generation cephalosporin. | Perioperative prophylaxis in selected operations, surgical-site/skin infections, respiratory and biliary infections. | 1.5 g IV every 8 h for treatment. For prophylaxis, commonly 1.5 g IV at induction, with re-dosing in long procedures according to protocol. | Allergy, diarrhoea, C. difficile. Renal adjustment in significant impairment. No reliable anaerobic cover, so add metronidazole for colorectal/anaerobic contamination where indicated. |
Important combinations to say in viva
- Ceftriaxone + metronidazole: Common regimen for community-acquired intra-abdominal infection because ceftriaxone covers many enteric Gram-negative organisms and metronidazole adds anaerobic cover.
- Ciprofloxacin/levofloxacin + metronidazole: Alternative in selected patients, particularly with beta-lactam allergy, but use only if local resistance and cultures permit.
- Piperacillin-tazobactam: Single-agent broad therapy for severe polymicrobial intra-abdominal infection.
- Meropenem: Reserve for severe infection with high likelihood of ESBL/resistant Gram-negative organisms, or culture-proven susceptibility.
- Linezolid: Add only if resistant Gram-positive infection such as MRSA/VRE is suspected or proven. It does not provide Gram-negative or anaerobic cover.
Common examiner follow-up questions
-
Why metronidazole is added to ceftriaxone?
Ceftriaxone lacks dependable anaerobic activity. Metronidazole provides anaerobic, especially Bacteroides, coverage. -
Does piperacillin-tazobactam cover anaerobes?
Yes. It covers many anaerobes, so metronidazole is not routinely added. -
Does meropenem cover MRSA?
No. Meropenem does not reliably cover MRSA or VRE. -
Which are anti-pseudomonal?
Piperacillin-tazobactam, meropenem, ciprofloxacin, and levofloxacin has variable activity depending on local susceptibility. -
Which drugs need renal dose adjustment?
Fluoroquinolones, cefotaxime, piperacillin-tazobactam, meropenem, cefuroxime, and usually amoxicillin-clavulanate. Check the hospital formulary. -
Which can cause QT prolongation?
Ciprofloxacin and levofloxacin. Be cautious with other QT-prolonging medicines and electrolyte disturbances. -
What is the most dangerous complication of paracetamol overdose?
Acute hepatic failure from hepatocellular necrosis. -
What is the specific antidote for lignocaine systemic toxicity?
20% intravenous lipid emulsion, alongside resuscitation.
For surgical infections, source control is as important as antibiotics: drainage of an abscess, repair/resection of perforation, debridement of necrotic tissue, and culture collection before antibiotics when this does not delay treatment. Antibiotic therapy should then be narrowed or stopped according to cultures and clinical response. Recent evidence also supports avoiding unnecessarily prolonged prophylaxis and using stewardship-based protocols, as summarized in a 2024 systematic review.
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