Niacin Ingested at Night Causes Severe Hypotension
Abstract
Four healthy subjects were studied during rest while in a seated posture in a moderately warm environment (T(a) = 30 C, rh = 23%) at 0800 h and again between 1800 and 2100 h. Evening experiments were done approximately 4 h before each subject went to bed. Esophageal temperature (T(es)), mean weighted skin temperature (T bar (sK)), forearm blood flow (FBF, venous occlusion plethesmography), skin blood flow (SkBF, laser doppler velocimetry), mean arterial pressure (MAP) and heart rate (HR) were measured twice each minute. After instrumentation, a 15 minute control period was initiated. T(es) and T bar (sK) were 0.4 (p < or =0.05) and 0.6 C higher at 1800 h than 0800 h. SkBF was 47 % higher (p < or =0.05) and cutaneous vascular conductance (CVC) was 43% greater (p < or =0.05) at 1800 h. Five mg niacin per kg body weight was ingested after the control period. Since onset time for niacin effects showed individual variability, the data were compared during pretreatment, the time of maximal vasodilation, and when T(es) was minimal. Niacin treatment during the morning and evening resulted in decreased T(es) and MAP and increased T bar (sK), SkBF, FBF, heart rate, and CVC (p < or = 0.05). Peak HR at 1800 h was 25 b min higher than at 0800 h (p < or = 0.05). MAP decreased an average of 12 Torr in the morning experiments and nearly 16 Torr in the evening experiments. Two of the subjects experienced severe hypotension after niacin treatment at 1800 h. A diurnal factor, presumably influencing the responsiveness of the cardiovascular system, may play a role in the hypotensive effect of niacin at night.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1989
- Accession Number
- ADA217896
Entities
People
- Lou A. Stephenson
- Margaret A. Kolka
Organizations
- United States Army Research Institute of Environmental Medicine