Dimenhydrinate Dosage for Motion Sickness
For motion sickness prevention and treatment, dimenhydrinate is recommended at a dose of 50-100 mg every 4-6 hours for adults, not to exceed 400 mg in 24 hours, and for children, 1.25 mg/kg or 37.5 mg/m² four times daily, not to exceed 300 mg daily. 1
Adult Dosing
Oral Administration
- Standard dose: 50-100 mg every 4-6 hours
- Timing: Take 30-60 minutes before travel or exposure to motion
- Maximum daily dose: 400 mg
Injectable Form (when oral form is impractical)
- Intramuscular: 50 mg (1 mL) as needed
- Intravenous: 50 mg (1 mL) diluted in 10 mL of 0.9% Sodium Chloride Injection, administered over 2 minutes
Pediatric Dosing
- Intramuscular: 1.25 mg/kg or 37.5 mg/m² four times daily
- Maximum daily dose: 300 mg
- Note: Not recommended for children under certain conditions (see contraindications)
Clinical Efficacy
Dimenhydrinate is probably more effective than placebo at preventing motion sickness symptoms under natural conditions, with a 40% prevention rate compared to 25% with placebo 2. As a first-generation antihistamine, it works by blocking histamine H1 receptors and has anticholinergic properties that help reduce vestibular stimulation.
Research shows that dimenhydrinate (100 mg) significantly reduces motion sickness symptoms compared to placebo, with an average symptom score 5.9 points lower 3. It may work by:
- Depressing central nervous system activity
- Suppressing abnormal gastric myoelectric activity (tachyarrhythmia)
Side Effects and Precautions
Common Side Effects
- Drowsiness: Significantly higher after dimenhydrinate administration compared to placebo 3
- Sedation: First-generation antihistamines like dimenhydrinate are more likely to cause sedation (66% vs 44% with placebo) 2
Precautions
- Avoid alcohol and other CNS depressants while taking dimenhydrinate
- Use caution when operating machinery or driving due to sedative effects
- May have abuse potential, particularly when combined with other substances 4
Clinical Pearls
- Dimenhydrinate is most effective when taken preventively, before motion exposure
- The sedating properties may be beneficial for long journeys where sleep is desirable
- Behavioral strategies should be used alongside medication:
- Positioning in the most stable part of the vehicle
- Watching the true visual horizon
- Minimizing head movements
- Lying down with eyes closed if symptoms worsen
Alternative Options
When dimenhydrinate is not suitable, consider:
- Scopolamine transdermal patch (first-line alternative)
- Other first-generation antihistamines
Note that nonsedating antihistamines, ondansetron, and ginger root have not shown effectiveness for motion sickness prevention or treatment 5, 6.