Simon asked
Can you list all of the potential side effects of Benadryl?
Answer
Benadryl (diphenhydramine) is a sedating "first-generation" antihistamine that is most commonly used for the treatment of seasonal allergies, allergic reactions and insomnia.
Side Effects Of Benadryl
Overall, Benadryl is well tolerated and side effects are generally mild in severity. If they do occur, they should subside 4 to 6 hours after dosing, although this can be extended in those with kidney disease and in the elderly. Below, we discuss the most common side effects associated with Benadryl.
Central Nervous System Effects
Benadryl is a central nervous system (CNS) depressant, which can commonly cause:
- Drowsiness
- Dizziness
- Sedation
- Somnolence
Other less frequently occurring CNS effects include:
- Weakness
- Confusion
- Slurred speech
- Muscular weakness
- Fatigue
- Headache
Rarely, Benadryl can cause paradoxical excitation, but is more likely to occur in children according to the prescribing information. In addition, certain individuals with genetic variations in the CYP2D6 metabolizing enzyme may be at a higher risk of excitation with Benadryl according to studies. Symptoms of Benadryl excitation include:
- Restlessness
- Anxiousness
- Agitation
- Insomnia
- Muscle spasms
- Nervousness
- Irritability
- Seizures
Symptoms of overdose of Benadryl often mirror symptoms of excitation and can include insomnia, nervousness or restlessness, irritability, and seizures.
Gastrointestinal System Effects
Benadryl has strong anticholinergic side effects, which include:
- Dry mouth (xerostomia)
- Constipation
- Abdominal pain
- Diarrhea
- Abdominal cramping
- Dry eyes
- Appetite changes
- Thickening of bronchial secretions
- Urinary retention
- Pupil dilation
- Blurred vision
Dermatologic Side Effects
Dermatological adverse effects of Benadryl are uncommon, but may include:
- Rash
- Ithcing
- Hives
- Photosensitivity
In addition, topical application of Benadryl can cause an allergic-type contact dermatitis, although this is thought to be rare.
Cardiovascular Effects
Cardiovascular effects of Benadryl do not typically occur at usual dosages and are more associated with an overdose. Potential symptoms include:
- Increased heart rate
- Palpitations
- Angina (chest pain)
- Heartbeat outside the normal rhythm
- Arrhythmias
- Hypotension and hypertension
Conclusion
As mentioned at the beginning of the article, most side effects of Benadryl are mild to moderate in severity. If they occur, they should subside relatively quickly. More severe side effects, such as cardiovascular reactions, are uncommon and typically occur only when high doses are taken.
