Quesiton 10

Question:

A patient self-administers a high, but non-toxic dose of a first-generation antihistamine. Which of the following symptoms is likely to be found in this patient?

Correct Answer: A.  Blurred vision

Anticholinomimetic actions are common side-effects of non-selective H1 antagonists. This can result in blurred vision and urinary retention.
H1-antagonists at high, non-toxic doses cause:
(1) central sedation (i.e. drowsiness with diphenhydramine), not hyperactivity;
(2) adrenergic-blocking (in high doses), so hypotension, not hypertension;
(3) anti-emetic action, so no nausea; and
(4) anti-cholinergic effects, so antiparkinsonism