Summary. Warfarin is a commonly used prophylactic agent for the prevention of thromboembolic disease. We hypothesized that racial background in¯uenced warfarin dosage, and tested this by recording the international normalized ratio (INR) in 867 patients aged 40±90 routinely passing through our Anticoagulation Service whose target INR was 2±3. Mean (95% con®dence interval) dose was 4´1 (4´0±4´2) mg/d in 737 Caucasians, 5´5 (4´9±6´1) mg/d in 72 Asians, and 6´7 (5´8±7´6) mg/d in 58 Afro-Caribbeans (P < 0´05) between each group). In a subgroup of 302 (41 Asians, 22 Afro-Caribbeans, 239 Caucasians), body mass index did not in¯uence warfarin use. Despite small numbers, we conclude that racial background, but not body mass index, is a determinant of warfarin dosage. The reasons for this could be genetic, cultural (diet related), or both.

Drug-induced parkinsonism is common. Many drugs are implicated, particularly typical and atypical antipsychotics, antidepressants, anticonvulsants and certain antiemetics and antihypertensives. Identifying the offending drug is important in reducing morbidity.