Trihexyphenidyl (Artane) for antipsychotic side effects

Trihexyphenidyl was first synthesised in the late 1940s and was originally used for Parkinson's disease, before levodopa and dopamine agonists transformed that field. In modern psychiatry it survives as an alternative to benztropine for managing antipsychotic-induced extrapyramidal symptoms (EPS). It is sold under many brand names worldwide, but in the US the original brand was Artane.

What it is used for

The FDA-approved indications for trihexyphenidyl include:

• All forms of parkinsonism, including drug-induced
• Adjunctive control of extrapyramidal disorders caused by antipsychotic medications such as phenothiazines, haloperidol, and thiothixene

In practice, that means it is used for the same problems as benztropine: tremor, rigidity, slowed movement (parkinsonism), and acute dystonia. Like other anticholinergics, it does not help — and may worsen — tardive dyskinesia.

How it differs from benztropine

The two drugs are pharmacologically very similar, but there are some practical differences:

• Onset and duration: Trihexyphenidyl has a relatively short half-life and is usually given two to four times a day. Benztropine has a longer half-life and is often dosed once or twice daily.
• Stimulating effect: Trihexyphenidyl tends to feel mildly stimulating. Some people prefer this; others find it makes anxiety or insomnia worse.
• Form: Trihexyphenidyl is widely available as tablets and an oral elixir. Benztropine is also available as an injection, which is why benztropine is often the emergency-room drug of choice for acute dystonia.
• Misuse risk: Trihexyphenidyl has historically been more associated with recreational misuse because of its euphoric and hallucinogenic effects at higher doses.

Typical dosing

For drug-induced EPS, dosing usually starts at 1 mg once or twice daily, increasing as needed. Most patients are managed with 5 to 15 mg/day in divided doses, although the exact range varies by indication and tolerance. Doses should be discussed with the prescriber, not adjusted independently.

Side effects to expect

Because trihexyphenidyl shares the same mechanism as other anticholinergics, the side effect profile will look familiar:

• Dry mouth, often pronounced
• Constipation
• Blurred vision and difficulty focusing on close-up tasks
• Urinary hesitancy or retention
• Tachycardia
• Heat intolerance — anticholinergics reduce sweating, which raises the risk of overheating in summer or during exercise
• Confusion, especially in older adults or at higher doses
• Memory and attention impairment

The recreational misuse problem

Trihexyphenidyl is sometimes diverted and used recreationally, particularly in settings where stimulants are scarce. At low doses some people report a mild stimulating or euphoric feeling; at higher doses it can produce frank delirium with vivid hallucinations. This is one reason responsible prescribing involves limited supplies and clear counselling. People with substance use histories should discuss this openly with their prescriber.

The cognitive question, revisited

Several studies have looked at the cognitive effects of long-term anticholinergic use in people with schizophrenia, and the picture is consistent: chronic use is associated with measurably worse memory and processing speed. The Schizophrenia Patient Outcomes Research Team (PORT) recommendations and many international guidelines (including NICE CG178) discourage routine, indefinite use of anticholinergics. They are best understood as bridging medications while the antipsychotic regimen is sorted out.

Practical principles

• Use the lowest effective dose for the shortest practical time.
• Reassess every few months whether it is still needed.
• If symptoms have settled, taper rather than stop abruptly.
• If you and your prescriber are reaching for an anticholinergic on an ongoing basis, that is a signal to consider switching the antipsychotic itself. See when to switch antipsychotics.

If trihexyphenidyl isn't working

Other options to discuss with your prescriber include benztropine, amantadine (for parkinsonism), and beta-blockers like propranolol (for akathisia). For acute dystonia, intramuscular benztropine or diphenhydramine is generally faster than oral trihexyphenidyl.

This article is for educational purposes only and is not medical advice, diagnosis, or treatment. Always consult a qualified mental health professional. If you or someone you know is in crisis, call or text 988 in the US, or your local emergency number.