link:
Diphenhydramine - Wikipedia, the free encyclopedia
Diphenhydramine, nytol
Side effects
Like many other first-generation antihistamines, diphenhydramine is a potent anticholinergic agent. This leads to profound drowsiness as a very common side-effect. Diphenhydramine has also been used as an anxiolytic because of these sedating side effects. However, other side effects include possibilities of motor impairment (ataxia), dry mouth and throat, flushed skin, increased heart rate (tachycardia), blurred vision at nearpoint owing to lack of accommodation (cycloplegia), abnormal sensitivity to bright light (photophobia), pupil dilation (mydriasis), urinary retention, constipation, difficulty concentrating, short-term memory loss, visual disturbances, hallucinations, irregular breathing, dizziness, irritability, itchy skin, confusion, decreased body temperature (generally in the hands and/or feet), erectile dysfunction, excitability, and delirium[10]. Some side effects such as twitching may be delayed until the drowsiness begins to cease and the person is in more of an awakening mode. Diphenhydramine also has local anesthetic properties, and has been used for patients allergic to common local anesthetics like lidocaine.[11]
Diphenhydramine is similar in its effects to dimenhydrinate, its 8-chlorotheophylline salt, although the latter is approximately 60% the potency in terms of required dosage and is slightly less sedating.
Some patients have an allergic reaction to diphenhydramine in the form of hives.[12][13]
Since 2002, the US FDA requires special labeling warning against using multiple products that contain diphenhydramine.[14] Diphenhydramine has been shown to build tolerance against its sedation effectiveness very quickly, with placebo-like results after a third day of common dosage.[15]
Paradoxical reactions to diphenhydramine are documented, particularly amongst children, and it may cause excitation instead of sedation.[16][17]
Because of potential for more severe side effects, diphenhydramine is on the "Beers list" to avoid in the elderly. (See NCQA’s HEDIS Measure: Use of High Risk Medications in the Elderly,
http://www.ncqa.org/Portals/0/Newsroom/SOHC/Drugs_Avoided_Elderly.pdf).
Benadryl Itch Stopping Gel contains additional ingredients including camphor. It is dangerous when swallowed