Dizziness or lightheadedness may be more likely to occur in the elderly, who are more sensitive to the effects of phenoxybenzamine. In addition, phenoxybenzamine may reduce tolerance to cold temperatures in elderly patients.

In these two systems, the alpha 1 adrenergic receptor reappearance followed a monoexponential kinetic allowing to determine the half-life of the receptor (23h in vitro, 33h in vivo) as well as the rate of receptor synthesis and degradation.