Answer
The selected products advise avoiding other diphenhydramine-containing preparations because combined exposure can increase toxicity and overdose risk.
Sources for this answer
- Diphenhydramine Hydrochloride 25 mg Tablets 20's (P) (PL 43461/0065) — Current selected SmPCemc · Summary of Product Characteristics
- Histergan Cream — Current selected SmPCemc · Summary of Product Characteristics
General medicine information. Follow the instructions for your own medicine and speak to a pharmacist or clinician about your individual circumstances.