Somnicaps Side Effects
Generic name: diphenhydramine
Medically reviewed by Drugs.com. Last updated on Oct 4, 2021.
Note: This document contains side effect information about diphenhydramine. Some of the dosage forms listed on this page may not apply to the brand name Somnicaps.
For the Consumer
Applies to diphenhydramine: oral capsules and tablets, parenteral injection
Side effects include:
Sedation, sleepiness, dizziness, disturbed coordination, epigastric distress, thickening of bronchial secretions.
For Healthcare Professionals
Applies to diphenhydramine: compounding powder, injectable solution, oral capsule, oral disintegrating strip, oral liquid, oral tablet, oral tablet chewable, oral tablet disintegrating
The most commonly reported side effects included somnolence, dizziness, and incoordination.[Ref]
Common (1% to 10%): Sedation/somnolence/sleepiness, drowsiness, unsteadiness, dizziness, headache, attention disturbance
Rare (0.01% to 0.1%): Extrapyramidal effects, tremor, convulsions
Drowsiness usually diminishes after a few days.[Ref]
Common (1% to 10%): Dry mouth
Common (1% to 10%): Fatigue
Rare (0.01% to 0.1%): Confusion, depression, sleep disturbances
Rare (0.01% to 0.1%): Blood disorders
Rare (0.01% to 0.1%): Hypersensitivity reactions
Rare (0.01% to 0.1%): Liver dysfunction[Ref]
Frequency not reported: Blurred vision, dry eyes, diplopia[Ref]
Frequency not reported: Increased appetite, anorexia[Ref]
Frequency not reported: Muscle twitching/weakness[Ref]
Frequently asked questions
- How much Benadryl can I take? What is too much?
- What is the max dose of diphenhydramine for adults?
- Does diphenhydramine raise blood pressure?
- Can diphenhydramine be used as a sleep aid?
- Diphenhydramine Hydrochloride vs Citrate: What's the difference?
More about Somnicaps (diphenhydramine)
- Drug interactions
- Dosage information
- During pregnancy or Breastfeeding
- Drug class: anticholinergic antiemetics
- Latest FDA Alerts (2)
Related treatment guides
1. "Product Information. Benadryl (diphenhydramine)." Parke-Davis (2002):
2. "Product Information. Benadryl Children's Allergy Fastmelt (diphenhydrAMINE)." Pfizer U.S. Pharmaceuticals Group (2022):
3. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
4. Cerner Multum, Inc. "Australian Product Information." O 0
Some side effects may not be reported. You may report them to the FDA.