Influence of tiapride on platelet counts in healthy volunteers and patients with movement disorders

Abstract Background : The selective D2 antagonist tiapride is administered in various movement disorders. Furthermore, there are indications that tiapride increases platelet counts. Aim : To characterize tiapride's potential to increase platelet counts in healthy subjects and patients with movement disorders. Methods : In Part A, 10 healthy volunteers received tiapride (300 mg/day) for 21 days in a longitudinal, prospective, open trial. One hundred healthy subjects served as controls. Part B was a retrospective analysis of 15 patients with movement disorders on tiapride [Huntington's disease ( n =6), Morbus Little ( n =3), hyperkinetic syndromes of undetermined etiology ( n =3), blepharospasm ( n =1), cervical dystonia ( n =1), perioral dyskinesia ( n =1)] and 15 age- and sex-matched controls. Results : Part A: Although serum prolactin levels increased by 526±14%, confirming good drug compliance, tiapride elicited only minor changes in platelet counts. Part B: Platelet counts correlated positively with the dose of tiapride (100–800 mg/day; r =.67; P =.007). Platelet counts were significantly higher in patients on tiapride compared to healthy age-matched controls ( P Conclusion : Three weeks of treatment with tiapride (300 mg/day) is insufficient to elevate platelet counts to a clinically relevant extent in young healthy volunteers. However, in elderly patients with movement disorders tiapride treatment is associated with markedly increased platelet counts.