Typical drug doses for adults

Before you give any drug: quick safety framework

• Confirm: patient, drug, dose, route, time, allergy status, indication.
• Check weight (actual vs ideal), age, frailty, pregnancy, renal/hepatic function, and haemodynamic state.
• Start low and titrate: especially in the elderly, shocked, septic, hypovolaemic, or with cardiac disease.
• Know your concentration and syringe label (e.g., morphine 10 mg in 10 mL = 1 mg/mL).
• Have a plan for side effects: airway support, vasopressors, antiemetics, reversal agents.
• Document what you gave and the effect (BP/HR/ETCO2/SpO2/level of sedation).

Induction of anaesthesia (IV) — typical adult doses (titrate to effect)

• Propofol: 1.5–2.5 mg/kg IV (often less: 0.5–1.5 mg/kg in elderly/frail/shocked).
• Thiopentone: 3–5 mg/kg IV (reduce in elderly/hypovolaemia).
• Etomidate: 0.2–0.3 mg/kg IV (useful when cardiovascular stability is important).
• Ketamine: 1–2 mg/kg IV (or 4–6 mg/kg IM); consider 0.2–0.5 mg/kg IV for analgesic/sedation doses.
• Fentanyl (at induction): 0.5–2 micrograms/kg IV (higher doses for very stimulating surgery under senior guidance).
• Alfentanil: 5–20 micrograms/kg IV (rapid onset/shorter duration).
• Remifentanil: commonly started as infusion 0.05–0.3 micrograms/kg/min; boluses are specialist practice and can cause rigidity/apnoea.

Neuromuscular blockade (muscle relaxants) and reversal

• Rocuronium: 0.6 mg/kg IV for intubation (1.0–1.2 mg/kg for rapid sequence induction if appropriate).
• Suxamethonium: 1–1.5 mg/kg IV for rapid onset (avoid in hyperkalaemia risk, neuromuscular disease, major burns >24–48 h, crush injury, prolonged immobilisation).
• Atracurium: 0.5 mg/kg IV (histamine release can cause hypotension/flush).
• Cisatracurium: 0.15–0.2 mg/kg IV (often preferred in organ failure).
• Vecuronium: 0.1 mg/kg IV (slower onset; longer acting).
• Neostigmine reversal: 0.04–0.07 mg/kg IV with glycopyrrolate 0.01 mg/kg IV (typical adult: neostigmine 2.5 mg + glycopyrrolate 0.5 mg).
• Sugammadex (rocuronium/vecuronium): 2 mg/kg (moderate block), 4 mg/kg (deep block), 16 mg/kg (immediate reversal after high-dose rocuronium/failed intubation scenario).

Maintenance and sedation (common starting points)

• Sevoflurane: commonly ~1–2% end-tidal for maintenance (adjust to clinical signs and MAC; lower with opioids/elderly).
• Desflurane: commonly ~4–6% end-tidal (varies with age and co-administered drugs).
• Isoflurane: commonly ~0.8–1.5% end-tidal.
• Propofol TIVA (typical adult): induction then infusion commonly 4–10 mg/kg/h (titrate; consider lower in elderly).
• Remifentanil infusion: 0.05–0.3 micrograms/kg/min (titrate to stimulus and respiratory rate/ETCO2).
• Dexmedetomidine: 0.2–0.7 micrograms/kg/h infusion (loading doses often avoided due to bradycardia/hypotension).
• Midazolam sedation: 0.5–1 mg IV increments every few minutes; typical total 1–5 mg (less in elderly/frail).

Analgesia (perioperative) — typical adult doses

• Paracetamol: 1 g PO/IV every 6 hours (max 4 g/24 h; reduce max in low body weight or liver disease per local policy).
• Ibuprofen: 400 mg PO three times daily (avoid in renal impairment, GI bleeding risk, severe asthma sensitivity, and some surgical contexts).
• Diclofenac: 50 mg PO/PR up to three times daily (check local restrictions/cardiovascular risk; avoid in renal impairment).
• Morphine IV (titration): 1–2 mg every 3–5 min to effect (watch RR, sedation, BP); typical total in PACU varies widely.
• Morphine PO: 10–20 mg immediate release (opioid-naïve adults; lower in elderly).
• Oxycodone: 2–5 mg IV increments or 5–10 mg PO (opioid-naïve; reduce in elderly/renal impairment).
• Fentanyl IV analgesia: 25–50 micrograms boluses (repeat to effect).
• Tramadol: 50–100 mg PO/IV (max 400 mg/24 h; caution with seizures/serotonergic drugs).
• Ketamine analgesic adjunct: 0.1–0.3 mg/kg IV bolus then 0.05–0.2 mg/kg/h infusion (local practice varies).

Local anaesthetics (LA): common concentrations and safe dose thinking

• Always calculate maximum safe dose (mg/kg) before large-volume blocks; use local guidelines and consider lower limits in frail/elderly, pregnancy, liver disease, low muscle mass.
• Lidocaine (lignocaine): typical max 3 mg/kg plain; up to 7 mg/kg with adrenaline (epinephrine) (check local policy).
• Bupivacaine: typical max 2 mg/kg (lower threshold due to cardiotoxicity).
• Levobupivacaine: typical max 2 mg/kg.
• Ropivacaine: typical max 3 mg/kg (often less cardiotoxic than bupivacaine but still potentially dangerous).
• Common concentrations: lidocaine 1% = 10 mg/mL; lidocaine 2% = 20 mg/mL; bupivacaine 0.25% = 2.5 mg/mL; 0.5% = 5 mg/mL; ropivacaine 0.2% = 2 mg/mL; 0.75% = 7.5 mg/mL.
• If LA systemic toxicity (LAST) suspected: stop injecting, call for help, airway/ventilation, treat seizures, start lipid emulsion early per guideline.

Antiemetics (PONV prophylaxis/treatment) — typical adult doses

• Ondansetron: 4 mg IV (often near end of case).
• Dexamethasone: 4–8 mg IV at induction (consider glucose rise).
• Cyclizine: 50 mg IV/IM (can cause sedation, tachycardia).
• Droperidol: 0.625–1.25 mg IV (check local QTc policy).
• Metoclopramide: 10 mg IV/PO (avoid in Parkinson’s; dystonia risk).
• Use multimodal prophylaxis for high-risk patients (e.g., dexamethasone + ondansetron).

Vasopressors and inotropes (common theatre bolus/infusion doses)

• Phenylephrine: 50–100 micrograms IV bolus (pure vasoconstrictor; can cause reflex bradycardia).
• Metaraminol: 0.25–0.5 mg IV bolus; infusion often 1–10 mg/h (titrate).
• Ephedrine: 3–6 mg IV bolus (useful with bradycardia; less effective if catecholamine-depleted).
• Adrenaline (epinephrine) infusion: 0.02–0.2 micrograms/kg/min (senior-led; titrate carefully).
• Noradrenaline (norepinephrine) infusion: 0.02–0.2 micrograms/kg/min (common vasopressor; needs appropriate access and monitoring per local policy).
• Glycopyrrolate: 200–400 micrograms IV for vagal bradycardia (also paired with neostigmine).
• Atropine: 500 micrograms IV for bradycardia (repeat to max 3 mg).

Airway and emergency drugs (adult typical doses)

• Co-amoxiclav: 1.2 g IV (common surgical prophylaxis; check allergy and local guidelines).
• Cefuroxime: 1.5 g IV (example prophylaxis; local policy varies).
• Tranexamic acid: 1 g IV (often over 10 min) then consider further dosing/infusion depending on surgery and local protocol.
• Naloxone: 40–100 micrograms IV increments every 2–3 min (aim: adequate breathing, not full pain reversal).
• Flumazenil: 200 micrograms IV, then 100 micrograms every 1 min up to 1 mg (caution: seizures in mixed overdoses/benzodiazepine dependence).
• Adrenaline in cardiac arrest: 1 mg IV (10 mL of 1:10,000) every 3–5 min during CPR.
• Adrenaline in anaphylaxis (peri-arrest features): titrated IV boluses e.g., 10–50 micrograms; if less severe, IM 500 micrograms (0.5 mL of 1:1,000) into anterolateral thigh; follow local anaphylaxis guideline.

Dose adjustments: who needs less (and why)

• Elderly/frail: increased sensitivity to hypnotics and opioids; start with smaller doses and slower titration.
• Hypovolaemia/sepsis/haemorrhage: reduced circulating volume and cardiovascular reserve → induction agents can cause profound hypotension.
• Obesity: some drugs dose to ideal/lean body weight (e.g., propofol induction often closer to lean/adjusted; suxamethonium often to total body weight; rocuronium often to ideal/lean depending on context—follow local guidance).
• Renal impairment: active metabolites can accumulate (e.g., morphine); consider alternatives and lower dosing.
• Hepatic impairment: reduced metabolism and protein binding; increased sensitivity to sedatives/opioids.
• Pregnancy: reduced anaesthetic requirements and higher aspiration risk; follow obstetric anaesthesia protocols.