Pain is sensed, transmitted, and modified via a variety of mediators and their receptors.
Histamine is a well-known mediator of
pain. In addition to their antagonistic effects against
histamine,
classical antihistaminics possess, to various degrees, antimuscarinergic, antiserotonergic, antiadrenergic,
local anesthetic, membrane-stabilizing and other
pharmacologic actions. Although there have been many attempts to use
classical antihistaminics as
analgesics and/or
analgesic adjuvants, the appearance of non-steroidal anti-inflammatory drugs discouraged such efforts. Here, we compared the
analgesic effect of an
ointment containing 1%
diphenhydramine (a typical first-generation antihistaminic drug) with that of
indomethacin (a typical non-steroidal anti-inflammatory drug) in elderly patients with
osteoarthritis and/or
osteoporosis who complained of bone-joint-
muscle pain.
Analgesic effects were evaluated by measuring skin impedance and by subjective
pain assessments (using a visual recording system) before and after
ointment application.
Diphenhydramine ointment exerted a prompt and marked
analgesic effect that lasted for several hours, as assessed by either skin impedance or subjective
pain evaluation. In contrast, the
analgesic effect of
indomethacin ointment was marginal, and significant only an hour or more later than that of
diphenhydramine. These results suggest that
diphenhydramine ointment may be useful for the relief of the bone-joint-muscle pains that are common in elderly subjects.