Side Effects of Gravol (Dimenhydrinate)
The most frequent side effect of Gravol is drowsiness, followed by dizziness, with additional anticholinergic effects including dry mouth, blurred vision, and urinary difficulties that patients should be counseled about before use. 1
Common Side Effects
The FDA-approved drug label identifies the following adverse reactions in order of frequency:
- Drowsiness is the most common side effect and occurs frequently enough that patients should be warned about operating machinery or driving 1
- Dizziness is the second most common adverse reaction 1
- Anticholinergic symptoms including dry mouth, nose and throat, blurred vision, and difficult or painful urination are characteristic of this H1 antihistamine 1
- Gastrointestinal effects such as epigastric distress, anorexia, and paradoxically nausea can occur 1
- Respiratory symptoms including thickening of bronchial secretions may develop 1
Neuropsychiatric Effects
- Headache, nervousness, restlessness, or insomnia occur particularly in pediatric patients 1
- Lassitude and excitation represent paradoxical CNS effects 1
- Euphoria, anxiolysis, and hallucinations can occur with supratherapeutic doses due to anticholinergic properties, creating abuse potential 2, 3
Cardiovascular Effects
- Tachycardia (rapid heart rate) is listed as a potential adverse reaction 1
Dermatologic Effects
- Skin rash may develop in some patients 1
Serious Adverse Events (Overdose Context)
While rare at therapeutic doses, massive overdoses have resulted in:
- Status epilepticus and ventricular dysrhythmias can occur rapidly, with death possible within two hours of massive ingestion 4
- Severe CNS stimulation including seizures represents the most dangerous complication of overdose 4
Clinical Context for Safe Use
The American Gastroenterology Association recommends dimenhydrinate as a safe first-line antiemetic option for nausea and vomiting of pregnancy at 25-50 mg three times daily. 5 This guideline context confirms its safety profile when used appropriately, though the anticholinergic side effects remain relevant even at therapeutic doses 1.
Common Pitfall to Avoid
Do not dismiss patient reports of drowsiness or dizziness as trivial—these are the most frequent adverse effects and warrant counseling about avoiding activities requiring alertness 1. Additionally, screen for potential abuse in patients with psychiatric histories, as the medication has documented abuse liability for its euphoric and anxiolytic effects at high doses 2, 3.