Quetiapine and Trihexyphenidyl interaction
Quetiapine and Trihexyphenidyl: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Trihexyphenidyl (Trihexyphenidyl Hydrochloride) label · effective 2025-07-02
Neuroleptic Malignant Syndrome A potentially fatal symptom complex sometimes referred to as Neuroleptic Malignant Syndrome (NMS) has been reported in association with dose reduction or Discontinuation of trihexyphenidyl.
Prophylactic administration of anticholinergic agents, such as trihexyphenidyl, as a prevention of drug-induced parkinsonism during neuroleptic therapy is not recommended.
Concurrent use of alcohol or other CNS depressants with trihexyphenidyl HCl may cause increased sedative effects.
There may be an increased risk for the development of tardive dyskinesia during concomitant administration of anticholinergics and neuroleptics ( see PRECAUTIONS , General ).
From the Quetiapine (SEROQUEL XR) label · effective 2026-04-10
• Anticholinergic (antimuscarinic) Effects: Use with caution with other anticholinergic drugs and in patients with urinary retention, prostatic hypertrophy, or constipation (5.20)
Other important considerations in the differential diagnosis include central anticholinergic toxicity, heat stroke, drug fever, and primary central nervous system (CNS) pathology.
This contributes to anticholinergic adverse reactions when SEROQUEL XR is used at therapeutic doses, taken concomitantly with other anticholinergic medications, or taken in overdose.
SEROQUEL XR should be used with caution in patients receiving medications having anticholinergic (antimuscarinic) effects [see Drug Interactions (7.1) , Overdosage (10.1) , and Clinical Pharmacology (12.1) ] .
Anticholinergic Drugs: Concomitant treatment with quetiapine and other drugs with anticholinergic activity can increase the risk for severe gastrointestinal adverse reactions related to hypomotility.
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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.