Medications Contraindicated with Dimenhydrinate
Dimenhydrinate is contraindicated with medications that may cause additive central nervous system depression, anticholinergic effects, or ototoxicity masking, including alcohol, other CNS depressants, anticholinergic drugs, and certain antibiotics.
Mechanism of Action and Composition
Dimenhydrinate (Dramamine) is composed of diphenhydramine and 8-chlorotheophylline. Its primary mechanism of action is H1-histamine receptor antagonism, with significant anticholinergic properties 1. Understanding this helps explain the potential drug interactions.
Specific Contraindications and Drug Interactions
1. CNS Depressants
- Alcohol and other CNS depressants: Concomitant use can have an additive sedative effect, significantly impairing mental and physical abilities 1
- Benzodiazepines: May enhance CNS depression, increasing risk of excessive sedation
- Opioids: Combined use may increase risk of sedation and respiratory depression
2. Anticholinergic Medications
- Other antihistamines: Additive anticholinergic effects
- Tricyclic antidepressants: Increased risk of anticholinergic side effects
- Antipsychotics: May enhance anticholinergic effects and increase risk of adverse reactions
3. Medications with Ototoxic Potential
- Certain antibiotics: Dimenhydrinate can mask symptoms of ototoxicity from antibiotics, potentially allowing progression to irreversible damage 1
4. Cardiac Medications
- Class I and Class III antiarrhythmics: Increased risk of QT prolongation
- Amiodarone, flecainide, propafenone, quinidine: Contraindicated due to risk of cardiac arrhythmias 2
5. Other Important Interactions
- Monoamine oxidase inhibitors (MAOIs): Can potentiate anticholinergic effects 2
- CYP3A inhibitors or inducers: May affect metabolism of dimenhydrinate
- Drugs with narrow therapeutic indices: Caution due to potential for altered metabolism
Special Populations and Considerations
Pediatric Patients
- Dimenhydrinate should be used with caution in children due to risk of paradoxical excitation 1
- Contraindicated in neonates due to benzyl alcohol content in some formulations 1
Elderly Patients
- Increased risk of dizziness and falls in elderly patients 3
- Second-generation antihistamines may be safer alternatives 3
Patients with Specific Conditions
Dimenhydrinate should be used with caution in patients with:
- Prostatic hypertrophy
- Stenosing peptic ulcer
- Pyloroduodenal obstruction
- Bladder neck obstruction
- Narrow-angle glaucoma
- Bronchial asthma
- Cardiac arrhythmias 1
Overdose Risk and Abuse Potential
Dimenhydrinate has abuse potential due to its ability to cause euphoria, hallucinations, and anxiolytic effects in high doses 4, 5. This risk increases when combined with other substances. Severe overdose can lead to status epilepticus, ventricular dysrhythmias, and potentially death 6.
Clinical Recommendations
- Always obtain a complete medication history before prescribing dimenhydrinate
- Consider alternative antiemetics in patients taking contraindicated medications
- Second-generation antihistamines may be preferable for patients at risk of CNS effects 3
- Monitor patients on multiple medications for signs of excessive sedation or anticholinergic effects
- Educate patients about avoiding alcohol and other CNS depressants while taking dimenhydrinate
By carefully screening for contraindications and monitoring for potential drug interactions, clinicians can minimize the risk of adverse effects associated with dimenhydrinate use.