Direct Thrombin Inhibitor (DOAC) Pregnancy: Avoid — limited data; use LMWH in pregnancy.

Dabigatran (Elderly AF — DOAC)

Brand names: Pradaxa

Adult dose

Dose: AF stroke prevention ≥80 years: 110 mg twice daily; age <80 years: 150 mg twice daily (standard). Consider 110 mg BD if age ≥75 or high bleeding risk

Route: Oral (swallow capsules whole — do not crush)

Frequency: Twice daily

Max: 150 mg BD (standard); 110 mg BD (elderly/high-risk)

Unique feature: only DOAC with a specific licensed lower dose for elderly (110 mg BD for ≥80 years). Renal clearance 80% — accumulates significantly in CKD. Antidote: idarucizumab (Praxbind). Cannot use in significant renal impairment (eGFR <30). Must store in original packaging (moisture-sensitive).

Paediatric dose

Route:

Licensed in paediatrics for VTE treatment (≥8 years) — specialist use only; not for AF indication.

Dose adjustments

Renal

eGFR 30–49: 110 mg BD (mandatory reduction). eGFR <30: contraindicated. Check eGFR at least annually in all elderly patients — MHRA recommendation.

Hepatic

Avoid in severe hepatic impairment (hepatic coagulopathy).

Clinical pearls

RE-LY trial (Connolly et al. NEJM 2009): dabigatran 150 mg BD vs warfarin in non-valvular AF — 34% relative risk reduction in stroke/SE with 150 mg; non-inferiority with 110 mg; major bleeding similar to warfarin (less ICH but more GI bleeding)
Idarucizumab (Praxbind): specific reversal agent — 5 g IV (two 2.5 g vials) reverses dabigatran within minutes; REVERSE-AD trial confirmed rapid complete reversal; available in UK EDs and hospitals
GI bleeding in elderly: dabigatran has higher GI bleeding rate than warfarin (and than apixaban); apixaban has lowest overall bleeding rate of all DOACs in elderly — consider if GI bleeding history. ARISTOTLE trial showed apixaban superiority in reducing major bleeding vs warfarin
Dyspepsia: occurs in ~10% of patients — often resolves; advise taking with food or a full glass of water. PPIs can be added (reduce GI side effects AND absorption slightly — acceptable)

Contraindications

eGFR <30 mL/min
Active major bleeding
Prosthetic heart valves (RE-ALIGN showed increased thromboembolism — DOAC contraindicated)
Concomitant dronedarone or systemic ketoconazole (P-gp inhibitors — significantly increased levels)

Side effects

Major bleeding (GI bleeding rate higher than warfarin — MHRA 2011 warning)
Dyspepsia and GI intolerance (characteristic — due to tartaric acid excipient)
Minor bleeding (bruising, epistaxis)
Hepatotoxicity (rare — monitor LFTs)

Interactions

P-gp inhibitors: verapamil (increases dabigatran AUC 180% — reduce to 110 mg BD if unavoidable); ketoconazole (contraindicated); amiodarone (minor interaction — monitor); clarithromycin (+20% exposure)
P-gp inducers: rifampicin, St John's Wort (significantly reduced dabigatran levels — avoid)
Proton pump inhibitors: reduce dabigatran absorption by ~20% (but GI side effects also reduced — acceptable trade-off)

Monitoring

eGFR at baseline, then every 6–12 months (or when clinical deterioration) — renal clearance 80%
LFTs (hepatotoxicity monitoring — baseline and annually)
Bleeding signs (GI, urinary, cutaneous)
Drug interactions review at every medication reconciliation

Reference: BNFc; BNF 90; RE-LY Trial (Connolly et al. NEJM 2009); REVERSE-AD Trial (Pollack et al. NEJM 2017); NICE NG196 (AF); MHRA Drug Safety Update 2011. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways