Carbimazole

Pregnancy & gynaecology-specific. Every dose row is source-referenced; verify against institutional protocols.

CarbimazoleAntithyroid agent

Regimens checked: 2026-10-17. Each indication has its own preparation, limits and safety checks.

Carbimazole: indication-specific regimens
Indication	Dose	Route	Frequency	Duration / preparation	Maximum	Monitoring / cautions
Specialist antithyroid option; pregnancy timing and PTU suitability determine selection Manufacturer / emcchecked	Adult product initial range 20–60 mg/day in 2–3 divided doses; maintenance usually 5–15 mg/day. Pregnancy requires the lowest effective dose. When switching, PTU 200 mg/day is approximately carbimazole 10 mg/day (20:1)	Oral	Initially divided 2–3 times daily; maintenance may be once daily	Reassess TFTs within 2 weeks after a switch/dose change; continuation through pregnancy and after birth is individualised · Use the stated tablet strength to deliver the exact mg; carbimazole and methimazole are not mg-for-mg equivalent RCOG advises considering PTU→carbimazole if antithyroid treatment is still needed beyond 20 weeks, rather than an automatic switch at the end of trimester 1. Routine block-and-replace is not recommended.	60 mg/day is the adult label starting-range ceiling, not a routine pregnancy goal; thyroid-storm treatment is a separate regimen	Monitor FT4/TSH, fever/sore-throat agranulocytosis warning, liver symptoms; fetal/neonatal surveillance when indicated Contraindications / cautions Previous carbimazole/thiamazole-associated pancreatitis, serious marrow or liver disorder; first-trimester embryopathy risk requires specialist counselling

Pregnancy safety

First-trimester embryopathy risk; specialist risk-benefit choice

Lactation

Discuss maternal dose and infant monitoring using RCOG guidance