Could the increased antihypertensive efficacy of ketanserin in the elderly be due to altered pharmacokinetics?

Ketanserin is a serotonin S2-receptor antagonist that is an effective antihypertensive agent with a greater blood pressure reduction in older patients. We have reviewed the data from two studies of ketanserin pharmacokinetics in elderly patients, one in general practice (GP) and one in hospital patients. We compared these data with the results from two of our previous studies in young volunteers. The purpose was to determine whether the enhanced efficacy of ketanserin in elderly hypertensive patients could be due to altered pharmacokinetics. After a single dose of ketanserin, elderly hypertensives showed about a 60% increase in bioavailability compared with young volunteers. This increase is likely to be explained by a reduced metabolism of ketanserin on first pass through the liver. The elimination half-life of ketanserin was found to be longer in elderly hospital outpatients, but not in our elderly subjects in general practice. This prolongation of the elimination half-life of ketanserin appears to be unrelated to age, since the hospital outpatient elderly and elderly subjects in general practice were of similar ages. The elimination half-life of ketanserinol was longer in the hospital elderly subjects. This probably reflects a slight diminution of renal function in the elderly hospital outpatients, resulting in reduced clearance of ketanserinol. The peak and trough ketanserin concentrations were similar in young and elderly subjects during chronic treatment, and it is therefore unlikely that the increased efficacy of ketanserin in elderly patients is due to altered pharmacokinetics.