MEDizzy - A 26-year-old woman has rhinorrhea, excessive lacrimation,

Feed Library Learning Discuss Leaderboard Journal

Pharmacology of peripheral nervous system 2

A 26-year-old woman has rhinorrhea, excessive lacrimation, and ocular congestion from a bout with the common cold. Diphenhydramine pro- vides symptomatic relief. Which of the following is the most likely mechanism by which this drug gave symptom relief in the presence of this rhinovirus?

ExplanationYou may have chosen d (histamine H1 receptor blocker) as your answer to this question. However, although diphenhydramine is an “antihistamine,” histamine plays a minor role in the symptoms of rhinovirus infections (in contrast with a much more important role in, say, seasonal allergies). As a result, blocking the effects of histamine on its receptors does not cause profound symptom relief in this situation. The drying up of nasal secretions afforded by diphenhydramine (an ethanolamine-type H1 blocker and the prototype of the first-generation agents) in this instance is due to the drug’s rather intense muscarinic receptor-blocking (atropine-like) actions.