Screen for respiratory disease, seizure history, glaucoma, and urinary obstruction before recommending dimenhydrinate.
Absolute contraindications include hypersensitivity to dimenhydrinate or diphenhydramine. Use caution in asthma, COPD, seizure disorders, angle-closure glaucoma, gastrointestinal or urinary obstruction, and hepatic dysfunction due to heightened anticholinergic and sedative effects.
Cross-reactivity with other ethanolamine antihistamines can provoke anaphylaxis or severe rash.
Combination may cause severe anticholinergic and CNS adverse effects.
Increased risk of paradoxical excitation and respiratory depression—require specialist guidance.
Anticholinergic drying can thicken secretions; use only with clinician oversight.
Anticholinergic effects may precipitate acute glaucoma attack.
CNS excitation or lowered seizure threshold possible; monitor closely if use is necessary.
May worsen difficulty urinating; consider alternatives.
Discuss risks and benefits; dimenhydrinate is generally considered low risk short term but may cause infant sedation during breastfeeding.