Dimenhydrinate Injection Dosing in Children
For intramuscular administration in children, the dose is 1.25 mg/kg of body weight (or 37.5 mg/m² of body surface area) administered four times daily, with a maximum daily dose not exceeding 300 mg. 1
Converting to mL/kg for 50 mg/mL Concentration
Since dimenhydrinate injection is supplied as 50 mg/mL, the volume-based dosing is:
- 0.025 mL/kg per dose (1.25 mg/kg ÷ 50 mg/mL = 0.025 mL/kg)
- Given four times daily (every 6 hours)
- Maximum 300 mg/day total
Route-Specific Administration
Intramuscular (IM):
- Inject 0.025 mL/kg (1.25 mg/kg) directly as needed, up to four times daily 1
Intravenous (IV):
- Must dilute each 1 mL (50 mg) in 10 mL of 0.9% Sodium Chloride Injection
- Inject over a period of 2 minutes 1
- Calculate the child's dose in mg, then dilute accordingly
Important Clinical Considerations
Common pitfalls to avoid:
- Do not exceed 300 mg total daily dose regardless of weight 1
- IV administration requires mandatory dilution—never give undiluted IV
- The drug causes drowsiness, which should be anticipated 1
Practical example: A 20 kg child would receive:
- 1.25 mg/kg × 20 kg = 25 mg per dose
- Volume: 0.5 mL of the 50 mg/mL solution
- Can be given up to 4 times daily (total 100 mg/day, well below 300 mg maximum)
The FDA-approved labeling provides clear weight-based dosing that is straightforward to calculate and does not require complex allometric scaling for this antihistamine medication 1.