Diphenhydramine and Haloperidol interaction
Diphenhydramine and Haloperidol: both prescribing labels describe an interaction that usually calls for monitoring, a dose change, or spacing the doses.
Usually manageable with monitoring or a dose change. Tell your pharmacist you take both.
What the FDA labels say
From the Diphenhydramine label · effective 2026-03-05
Drug Interactions Diphenhydramine hydrochloride has additive effects with alcohol and other CNS depressants (hypnotics, sedatives, tranquilizers, etc).
From the Haloperidol (Haldol Decanoate) label · effective 2025-11-11
CYP3A4 and/or CYP2D6 Inhibitors Clinical Impact CYP3A4 and/or CYP2D6 inhibitors increase haloperidol exposure (haloperidol is a CYP3A4 and CYP2D6 substrate) [see Clinical Pharmacology (12.3) ].
Concomitant use of HALDOL DECANOATE and CYP3A4 and/or CYP2D6 inhibitors may increase the risk of haloperidol-associated adverse reactions.
Anticholinergic Drugs Clinical Impact The healthcare provider should keep in mind the possible increase in intraocular pressure when anticholinergic drugs are administered concomitantly with HALDOL DECANOATE.
Table 3: Other Clinically Significant Drugs Interactions See www.fda.gov/CYPandTransporterInteractingDrugs for examples of CYP3A4 and/or CYP2D6 inhibitors, CYP3A4 inducers, and CYP2D6 substrates.
CYP2D6 Substrates Clinical Impact Haloperidol is a CYP2D6 inhibitor.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.