Rina asked
I am wondering about the side effects of Benadryl. Does it cause constipation.?
Answer
Benadryl (diphenhydramine) may cause constipation, diarrhea, or abdominal pain in some patients.
Benadryl and other antihistamines have anticholinergic effects which can cause dry mouth, dry eyes, thickening of bronchial secretions, urinary retention, blurred vision, drowsiness, and decreased gut motility (i.e. slower movement through the GI tract).
Benadryl And First Generation Antihistamines - Constipation
Benadryl is a first-generation antihistamine and is more likely to cause anticholinergic side effects than second-generation antihistamines. Other first-generation antihistamines include Dramamine (dimenhydrinate), Chlor-Trimeton (chlorpheniramine), Tavist (clemastine), and Phenergan (promethazine), among others. All of these antihistamines can cause constipation due to their drying effects. In addition, these medications cross the blood-brain barrier and have CNS effects like drowsiness and dizziness.
The first generation antihistamines are also listed as medications to avoid in elderly adults by the Beers Criteria due to the increased risk of confusion, dry mouth, and drowsiness.
Second Generation Antihistamines - Constipation
Second generation antihistamines include Claritin (loratadine), Cetirizine (Zyrtec), and Allegra (fexofenadine) and are much less sedating. Antihistamines are widely used for self-care of allergy symptoms including runny nose, watery eyes, sneezing, and itching of the nose, throat, or eyes. Benadryl may also be used for symptoms of the common cold, allergic reactions, occasional insomnia, and more.
Other Constipation Causing Medications
Other medications that can cause constipation include the following:
- Opioids like oxycodone, hydrocodone, morphine, codeine, and hydromorphone
- Antidepressants like paroxetine (Paxil), duloxetine (Cymbalta), and venlafaxine (Effexor)
- Blood pressure/heart medications like verapamil (Calan) and diltiazem (Cardizem)
- Supplements containing iron
- Other anticholinergics like oxybutynin (Ditropan)
Treatment of Benadryl Induced Constipation
Discontinuing the offending medication is usually the best treatment for constipation caused by medications. Other treatments for constipation include:
- Stool softeners like docusate (Colace)
- Osmotic agents like polyethylene glycol (Miralax)
- Stimulant laxatives like Bisacodyl (Dulcolax) and senna (Senokot)
- Fiber sources (Metamucil)
Summary
Benadryl (diphenhydramine) can have significant anticholinergic effects in individuals, which includes constipation. While many times medications like Benadryl can be to blame for constipation, other causes should also be considered. Aside from medications some other constipation causes lack of water intake, lack of dietary fiber, stress, and physical inactivity.
