Pediatric Dimenhydrinate (Gravol) Dosing
For children requiring dimenhydrinate, administer 1.25 mg/kg intramuscularly or intravenously every 6 hours, with a maximum daily dose of 300 mg, though this medication should be used cautiously given its limited benefit and potential to delay diagnosis of serious conditions. 1
Weight-Based Dosing
- Standard dose: 1.25 mg/kg per dose administered every 6 hours (four times daily) 1
- Alternative calculation: 37.5 mg/m² of body surface area four times daily 1
- Maximum daily dose: 300 mg regardless of weight 1
Route of Administration
- Intramuscular (IM): Each milliliter (50 mg) injected as needed 1
- Intravenous (IV): Each milliliter (50 mg) must be diluted in 10 mL of 0.9% Sodium Chloride and injected over 2 minutes 1
- Oral/rectal formulations: Available but specific pediatric dosing not detailed in FDA labeling 1
Dosing Interval
- Every 4-6 hours as needed for nausea and vomiting control 1
- Duration of action is approximately 4 hours per 50 mg adult dose 1
Age and Safety Considerations
Toxicity Thresholds
- Children under 6 years: Refer to emergency department if ingestion ≥7.5 mg/kg 2
- Children 6 years and older: Refer to emergency department if ingestion ≥7.5 mg/kg or 300 mg (whichever is less) 2
Important Clinical Caveats
Risk of diagnostic delay: Dimenhydrinate use is associated with delayed presentation (>12 hours after symptom onset) and can mask serious conditions including asthma, pelvic inflammatory disease, and urinary tract infection 3
Limited clinical benefit: While dimenhydrinate reduces vomiting frequency (69.6% vomiting-free vs 47.4% placebo), it does not improve oral rehydration success, weight gain, or clinical outcomes in children with gastroenteritis 4
Seizure risk with repeated dosing: Case reports document generalized tonic-clonic seizures in infants receiving repeated suppository doses (23 mg/kg over 2 days), particularly when defecation is intermittent and drug accumulates 5
Practical Dosing Examples
For a 20 kg child:
- Single dose = 1.25 mg/kg × 20 kg = 25 mg per dose
- Maximum frequency = every 6 hours
- Maximum daily = 300 mg (12 doses theoretically, but limited to 4 doses/day per FDA guidance) 1
For a 10 kg child:
- Single dose = 1.25 mg/kg × 10 kg = 12.5 mg per dose
- Every 6 hours as needed 1
When to Avoid or Use Cautiously
- Do not use in children with suicidal intent, intentional abuse, or suspected malicious intent 2
- Avoid when vomiting may indicate a treatable medical condition requiring prompt diagnosis 3
- Consider alternatives (such as ondansetron) given dimenhydrinate's modest efficacy and potential for diagnostic delay 4, 3
- Monitor closely if using rectal formulations repeatedly, as accumulation can occur 5
Monitoring After Administration
- Observe for 6 hours post-ingestion if therapeutic dosing; if asymptomatic at 6 hours, emergency referral not needed 2
- Watch for excessive drowsiness, agitation, seizures, or respiratory depression warranting immediate emergency department referral 2
- Assess whether vomiting cessation allows successful oral rehydration 4