Clinical Tool Real-time Calculation

Drug Calculator

Local anaesthetic maximum dose · Volume calculator · Opioid dose converter

⚠ Clinical tool for healthcare professionals only. Results are for guidance only. Always verify against local formulary, current BNF/SmPC, and individual patient factors. The site owner accepts no liability for clinical decisions made using this tool.

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Local Anaesthetic — Maximum Dose Calculator

Patient Weight (kg)

Local Anaesthetic

Concentration (%)

Planned Volume (mL) (optional)

Results

— Max dose (mg)

— Max volume (mL)

— Planned dose (mg)

— % of max dose

Max dose limits: Bupivacaine/Levobupivacaine 2 mg/kg · Ropivacaine 3 mg/kg · Lidocaine plain 3 mg/kg · Lidocaine + adrenaline 7 mg/kg · Mepivacaine 5 mg/kg · Prilocaine 6 mg/kg

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Concentration Quick Reference — mg/mL

Percentage concentration → mg/mL conversion (1% = 10 mg/mL)

Drug	0.125%	0.2%	0.25%	0.375%	0.5%	0.75%	1%	1.5%	2%
Ropivacaine	1.25	2	2.5	3.75	5	7.5	10	15	—
Bupivacaine	1.25	2	2.5	3.75	5	7.5	—	—	—
Levobupivacaine	1.25	2	2.5	3.75	5	7.5	—	—	—
Lidocaine	—	2	—	—	5	—	10	15	20
Mepivacaine	—	—	—	—	5	—	10	15	—

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Opioid Dose Converter — Oral Morphine Equivalents (OME)

From — Drug

Dose

To — Drug

Conversion Result

— Oral Morphine Eq. (mg)

— Converted dose

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Reduce by 25–50% when switching opioids (incomplete cross-tolerance). Always titrate to effect. These are approximate equivalences — individual variation is significant.

Drug & Route	Dose	OME (mg)	Ratio to PO Morphine
Morphine PO	10 mg	10	1 : 1
Morphine IV/SC	5 mg	10	1 : 3
Oxycodone PO	6.7 mg	10	1 : 1.5
Oxycodone IV	3.3 mg	10	1 : 3
Codeine PO	100 mg	10	0.1 : 1
Tramadol PO	100 mg	10	0.1 : 1
Fentanyl IV	100 mcg	10	100 mcg : 10 mg
Fentanyl Patch	25 mcg/h	~60/day	patch mcg/h × 2.4 = daily OME
Hydromorphone PO	1.3 mg	10	1 : 7.5
Hydromorphone IV	0.67 mg	10	1 : 15

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Infusion Rate Calculator

Drug & Concentration

Patient Weight (kg)

Desired Dose Rate

Dose Unit

Infusion Rate

— mL/hour

— Dose/hour

— 24h total dose

Local Anaesthetic Quick Reference

Ropivacaine Amide

Max dose	3 mg/kg
Available	0.2%, 0.375%, 0.5%, 0.75%, 1%
Onset	10–20 min
Duration	4–12 h (dose-dependent)
pKa	8.1
Protein binding	94%

Bupivacaine Amide

Max dose (plain)	2 mg/kg
Max dose (+adr)	2 mg/kg
Available	0.25%, 0.5%, 0.75% (spinal)
Onset	15–30 min
Duration	6–18 h
⚠ Cardiac toxicity	High — use with caution

Levobupivacaine Amide

Max dose	2 mg/kg
Available	0.25%, 0.5%, 0.75%
Onset	15–30 min
Duration	6–18 h
vs Bupivacaine	Less cardiotoxic — preferred in frail/elderly

Lidocaine Amide

Max dose (plain)	3 mg/kg
Max dose (+adr)	7 mg/kg
Available	0.5%, 1%, 2%
Onset	2–5 min
Duration	1–3 h (plain), 2–6 h (+adr)

Mepivacaine Amide

Max dose	5 mg/kg
Available	1%, 1.5%, 2%
Onset	3–10 min
Duration	2–4 h (plain), 4–6 h (+adr)
Note	Fast onset — useful for day-case

Prilocaine Amide

Max dose	6 mg/kg
Available	0.5%, 1%, 2%
Onset	5–10 min
Duration	1–3 h
⚠ Methaemoglobinaemia	Risk at high doses (>600 mg)

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LAST (Local Anaesthetic Systemic Toxicity): Intralipid 20% must be immediately available for all peripheral nerve blocks. Initial dose: 1.5 mL/kg IV bolus, then 0.25 mL/kg/min infusion. Max 12 mL/kg. Follow current AAGBI/ASRA LAST guidelines.