Diphenhydramine can interact negatively with several medications. Avoid combining it with alcohol or other central nervous system depressants like opioids (codeine, morphine), benzodiazepines (alprazolam, diazepam), or barbiturates. This combination significantly increases drowsiness and can impair coordination and judgment.
MAO inhibitors (used to treat depression) should also be avoided. Combining them with diphenhydramine elevates the risk of serious side effects. Consult your doctor before using diphenhydramine if you are taking MAO inhibitors.
Certain medications for allergies or colds can contain diphenhydramine, leading to accidental overdosing. Always check the labels of all over-the-counter medications to avoid combining products. This precaution is particularly relevant when using cough syrups or allergy medications.
Potential Interactions with Specific Medications
| Antihistamines | Cetirizine, Loratadine | Increased drowsiness, dry mouth |
| Muscle Relaxants | Cyclobenzaprine, Methocarbamol | Enhanced sedative effects |
| Antidepressants (certain types) | Tricyclic antidepressants | Increased risk of anticholinergic side effects (dry mouth, constipation, blurred vision) |
Precautions and Considerations
Diphenhydramine can cause significant drowsiness. Avoid driving or operating machinery after taking it. Be mindful of activities requiring alertness. It may worsen glaucoma or prostate problems. Inform your doctor about any pre-existing medical conditions before use.
Individuals with narrow-angle glaucoma, urinary retention, or a history of seizures should exercise particular caution and consult their doctor before using diphenhydramine. The medication can exacerbate these conditions.
Always follow the prescribed dosage carefully. Overdosing can lead to serious consequences. If an overdose is suspected, immediately contact your doctor or seek emergency medical assistance.
