title: [Is placebo necessary in a clinical trial on ambulatory blood pressure?].
abstract: Placebo has only a slight effect on ambulatory blood pressure (ABP). Some authors have suggested that the use of a placebo is not necessary in a study on the drugs effect on ABP. We demonstrate that even if placebo effect is small, the use of a placebo group is still necessary. Effects of one daily dose of 50 mg atenolol + 20 mg slow-released nifedipine (AN) were investigated. Patients with office DBP 90-110 mmHg received, in a double-blind protocol, either AN (group AN, n = 31) or a placebo (group P, n = 26). Ambulatory BP (ABP) and HR were measured (Spacelabs or Diasys systems) for 24 h before and one month after treatment. The 2 groups were comparable before treatment. After 1 month under treatment, ABP was significantly lower in the AN group, compared to the P group, and this over the whole day (p = 0.03 to p < 0.0001). The effect was the most important between 10-17 h (p < 0.0001). HR was significantly lower in the AN group during daytime (6-22 h), but not during the night (22-6 h). Over the whole group, placebo effect was not significant. However, ABP did decrease under placebo in subjects with high initial pressure. As a result, an analysis without data from the placebo group led to an overestimation of the effects of the drug.
authors.affiliation: URBB, INSERM U 263, université Paris 7.
authors.forename: N P
authors.initials: NP
authors.lastname: Chau
authors.forename: X
authors.initials: X
authors.lastname: Chanudet
authors.forename: D
authors.initials: D
authors.lastname: Mestivier
authors.forename: G
authors.initials: G
authors.lastname: Nguyen
mesh_terms: D000328:Adult; D000368:Aged; D001262:Atenolol / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D015924:Blood Pressure Monitors; D002986:Clinical Trials as Topic / Q000379:methods*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009543:Nifedipine / Q000494:pharmacology; D010919:Placebos
chemical_list: D010919:Placebos; D001262:Atenolol; D009543:Nifedipine
vernacular_title: Le placebo est-il nécessaire dans un essai clinique sur la pression artérielle ambulatoire?