Benzatropine

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Indication

Benzatropine (previously known as benztropine) is an unlicensed medicine indicated for use as an alternative treatment of hypersalivation secondary to clozapine treatment in patients for whom adequate trials of hyoscine hydrobromide (both tablets and transdermal patches), trihexiphenidyl and pirenzepine have been ineffective either due to lack of efficacy or side effects.

It must not be used first line due to the unlicensed status.

Benzatropine was previously licensed for the management of extrapyramidal side effects (EPSE) secondary to antipsychotic treatment. This protocol does not cover the use of benzatropine for this indication due to other licensed preparations being available.

Informed consent and documentation

Informed consent

Due to its unlicensed status, informed consent and explanation for the rationale of treatment choice must be obtained prior to treatment initiation.1 Patient information explaining unlicensed medication in general terms is available via Choice and Medication, as is a specific benzatropine leaflet. Where there is a lack of capacity, adherence to the principles contained in the Adults with Incapacity (Scotland) Act, 2000 is mandatory.

Documentation

The consultant psychiatrist must make a clear record of the rationale for prescribing an unlicensed medication within the patient’s case notes and document the discussion regarding consent.1

Prescribing

Inpatient:

  • Nursing staff in the ward must be informed of the medicine’s unlicensed status by the prescriber and ward clinical pharmacists must ensure that staff are aware of the unlicensed status.
  • When ordering benzatropine, the patient’s initials and CHI should be included on the requisition as well as the phrase "as per protocol" for the order to be processed.
  • A record of administration of unlicensed medication must be kept (as per unlicensed medication policy).2
  • This must include drug batch numbers, patient name and CHI number. The comments section of the recording sheet may be used for the purpose of documenting the batch number.
  • It is the responsibility of the nurse in charge to ensure this occurs.
  • When supplying benzatropine from pharmacy, pharmacy staff must ensure that batch numbers are documented on the prescription or requisition.

Outpatient:

The clozapine dispensary at Leverndale will supply benzatropine prescriptions after discharge to outpatients.

The standard clozapine out-patient prescription form will be used to prescribe benzatropine in addition to the patient’s regular clozapine dose.

Review:

Need for ongoing prescription of an unlicensed medicine should be assessed on a 6 monthly basis

Monitoring

There is no requirement for any specific monitoring.

Close monitoring of bowel function is mandatory with the combination of clozapine and benzatropine and should be reflected within the clozapine side effect monitoring care plan

Refer to the Guidelines for assessment and management of clozapine induced constipation for further information.

Dose range

Up to 2mg daily for hypersalivation.3,4

Benzatropine was licensed up to 6mg in divided doses for the management of EPSE.

Adverse effects

Adverse effects (frequency unknown):5,6

Tachycardia

Paralytic ileus

Constipation

Vomiting and nausea

Dry mouth

Confusion and memory impairment

Visual hallucinations

Nervousness

Depression

Numbness of fingers

Blurred vision

Dilated pupils

Urinary retention and dysuria

Skin rash

Heat stroke, hyperthermia and fever

Contraindications and cautions

Contraindications6:

• Hypersensitivity to benzatropine or any excipients

• Narrow angle glaucoma

• Tardive dyskinesia

• Pregnancy

Cautions6:

• Renal impairment

• Tachycardia

• Prostatic hypertrophy

• Glaucoma

Interactions:

May exacerbate the anticholinergic effects of other drugs including clozapine, especially constipation.

Alcohol can increase the sedative effects of benzatropine.

References

1. GMC Good practice in prescribing and managing medicines and devices. Updated Dec14 

2. NHS Greater Glasgow and Clyde Area Drug and Therapeutics Committee Policies Relating to the Management of Medicines Section 9.1 Acute Unlicensed Medicines Policy (ULM Policy)

3. Taylor D, Paton C, Kapur S. The Maudsley Prescribing Guidelines in Psychiatry; 13th edition: Wiley Blackwell

4. UKMi Medicines Q&A. Drug-induced hypersalivation- what treatment options are available? May17

5. Martindale. The Complete Drug Reference. Accessed 7/8/17

6. Prescribing Information. Benztropine 2mg. Pendopharm. Nov 2014 (obtained from Mawdsleys Brooks & Co)

Editorial Information

Last reviewed: 08 October 2020

Next review: 01 October 2023

Author(s): PMG-MH

Version: 1

Approved By: PMG-MH

Reviewer Name(s): Andrew Walker, Suzanne Burke