Benztropine injection for acute dystonic reactions

Treatment of acute dystonic reactions

The treatment of acute dystonia, including those induced by medicines such as antipsychotics or antiemetics, is a medical emergency (see the Royal College of Emergency Medicine (RCEM) guidance on acute dystonia).

The RCEM and National Poisons Information Service (NPIS) provide guidelines on antidote availability (see under toxicology and poisons section). Products should be immediately available in emergencies for treating dystonic reactions. The RCEM/NPIS joint guidance on antidote availability for emergency departments will be updated by mid 2026.

Procyclidine injection

Procyclidine 10mg/2ml solution for injection has been discontinued from the UK market.

NHS staff can find information on this discontinuation using the SPS Medicines supply tool Archived: Discontinuation of Procyclidine 10mg/2ml solution for injection ampoules (SPS page) (NHS email registration required).  

Benztropine injection

The Medicine Supply Notification on the discontinuation of procyclidine injection advised that benztropine mesylate injection is an injectable anticholinergic used to manage acute dystonic reactions. Further information is available on the SPS Medicines supply tool Archived: Discontinuation of Procyclidine 10mg/2ml solution for injection ampoules (SPS page) (NHS email registration required). Benztropine is also known as benzatropine (as per dm+d).

Benztropine licensing

Benztropine injection is unlicensed in the UK. Unlicensed imports of benztropine 2mg/2mL injection vials are available.

See our article on understanding unlicensed medicines Understanding unlicensed medicines (SPS page) for further information.

Dose of benztropine injection

Dose information can be found in product data sheets, Toxbase and the Royal College of Emergency Medicine guidance on acute dystonia.

There is no available information on dose equivalence with procyclidine.

Adults

• Administer 1-2mg intramuscularly (IM) or intravenously (IV)
• Administer a repeat dose if there has been no response after 30 minutes (IM) or 10 minutes (IV)

Maximum daily doses of 4-6mg have been reported

Children

Use is contraindicated in children under 3 years of age.

Children 3 years and over

• Administer 20-50 micrograms per kg (maximum 2mg) intramuscularly (IM) or intravenously (IV)
• Administer a repeat dose if there has been no response after 30 minutes (IM) or 10 minutes (IV)

Pharmacokinetics

The IM injection is reported to have a similar onset of action as the IV injection so intravenous administration is rarely necessary.

The duration of action of benztropine may persist for up to 24 to 48 hours following a single 2mg IM injection.

Caution

Consider the cumulative anticholinergic dosing, side effects and maximum doses in people prescribed regular oral procyclidine or trihexyphenidyl who subsequently need ‘as required’ injectable benztropine.

Consent to Treatment (Mental Health Act)

The Mental Health Act 1983 includes requirements for consent to treatment forms (T2/T3/S62) to include medicines used to alleviate the parkinsonian and other motor side effects of antipsychotic agents.

As benztropine is an unlicensed medicine, the Approved Clinician is responsible for making the choice on its use.

Benztropine injection must be listed on the form by name, along with the specific dosage, route and purpose for which it is to be administered. If a repeat dose may be appropriate, the form must reflect this and the daily maximum dose adjusted to allow for that.

For example: ‘Benztropine injection 1-2mg intramuscularly, repeated once, when required, up to a maximum dose of 4mg in 24hours for the treatment of acute dystonic reactions’

During the period when there may be overlap with the availability of procyclidine injection and benztropine injection, both options can be listed on the form with a statement to prescribe one or the other. This should only occur if it is appropriate for the individual patient.  Second Opinion Appointed Doctors (SOADs) have been made aware of this advice by the CQC.

The intravenous route is unlikely to be possible on a psychiatric ward but Approved Clinicians and SOADs might wish to consider whether the intravenous route should be specified as well.

The CQC have advised that any current forms that include procyclidine injection and require the inclusion of benztropine injection should be returned to the CQC to be amended. Please coordinate these updates locally with the pharmacy teams to determine when the procyclidine injection supplies will run out and when benztropine injection will be available.

Please contact your local Mental Health Act Officer for further advice.

Actions

Managing the use of a new medicine when a historical product is discontinued requires a coordinated response. NHS provider trust pharmacy procurement teams should work with clinical teams and local Medication Safety Officers (MSOs) to:

• review local stock holding for appropriateness
• engage early with specialist importers
• review and update local clinical guidelines
• communicate the change in practice to all impacted clinical areas
• ensure new products are prescribable on electronic prescribing and administration systems where appropriate

Holding unlicensed medicines as stock in clinical areas can present logistical governance challenges.

Consider how to locally manage supply of benztropine as an unlicensed medicine in an emergency situation, see Governance principles for unlicensed medicines (SPS page)

• Consider if risk assessment is needed to hold unlicensed stock within clinical areas.
• Ensure robust record‑keeping arrangements are in place, for example on patient medication charts or in local stock logs.
• Ensure there is organisational oversight of these records, including regular audit.

See the links below for further information:

• Advice related to making, purchasing and using unlicensed medicines – Unlicensed medicines (SPS page)
• The supply of unlicensed medicinal products ‘specials’, MHRA guidance note 14, Medicines and Healthcare products Regulatory Agency (MHRA)
• Prescribing unlicensed medicines, General Medical Council (GMC)

This page was developed with colleagues from other organisations including the College of Mental Health Pharmacy (CMHP), the Medication Safety Officer (MSO) Network and the Care Quality Commission (CQC).

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