Antipsychotic Depot injections

• Flupenthixol decanoate¹
• Fluphenazine decanoate²
• Haloperidol decanoate³
• Zuclopenthixol decanoate⁴
• Pipothiazine palmitate⁵
• Risperidone - the only atypical antipsychotic available as a depot preparation⁶

Depot antipsychotic agents were developed in the 1960s.⁷ Antipsychotic depot injections are an ester formulation of high-potency antipsychotics which when given intramuscularly provide slow release of the medicine, usually over 1-4 weeks. They are a good choice in patients with adherence problems towards oral antipsychotics.

Also see: Antipsychotics and Atypical Antipsychotics.

Specific points on antipsychotic medication also applies to the depot forms, including CSM advice.

• Schizophrenia - especially during maintenance therapy, occasionally in acute states. May be used to improve compliance or as a result of patient choice.⁸
• Schizoaffective disorder
• Psychotic states⁹

It is being increasingly recognised that depot preparations may have some use in the maintenance phase of bipolar disorder. However, they should be avoided in those patients with predominantly depressive symptoms.^10,11

Advantages

• Increased compliance - no need for daily tablets
• Long duration of therapy - ranges from 1-6 weeks
• Clopixol can be used in acute psychotic/manic states and may be useful in aggressive patients.
• Possibly reduced relapse rate
• Consistent delivery
• Not dependent on first-pass metabolism

Disadvantages

• Pain, erythema, swelling and nodule formation at site of injection
• Unable to terminate therapy if side effects occur - need to wait for it to wear off, therefore, always start with a test dose.
• Takes many weeks to reach steady state plasma levels

Contraindicated in children.

See individual drug monographs for full list of contraindications.

• Use lower doses in the elderly, such as, 25 - 50% of the recommended doses.
• Flupenthixol elevates mood but may worsen agitation.
• Fluphenazine - avoid in depression and is associated with a high incidence of extra-pyramidal side effects.
• Haloperidol is also associated with a high incidence of extra-pyramidal side effects.

One meta-analysis in 2001 reported the following¹³

• Relapse rates were significantly less in the group of patients taking depot medication in comparison to placebo or oral antipsychotics. However, data is limited in this area.
• Furthermore, side effect frequency was similar to oral antipsychotics - including the occurrence of tardive dyskinesias.
• Higher doses do not produce any further benefits compared with lower doses - in fact they can be more harmful due to increased risk of side effects.¹⁴

• Not suitable for children.
• There is no clear advantage of one depot over another.
• Should be under specialist guidance as there is a risk of relapse when oral antipsychotics are reduced.
• Need to tail off oral antipsychotics gradually when starting the patient on depot antipsychotics. Do not abruptly stop oral antipsychotics.
• Administer by deep intramuscular injection and rotate sites to avoid reactions.
• Start with a test dose - using lowest dose possible.
• Wait 4-10 days after the test dose before starting to titrate the dose.
• It can take several weeks to achieve steady state levels with depot antipsychotics.
• Flupenthixol can cause agitation in already agitated patients - Zuclopenthixol may be a better choice.
• Increased doses of depot medication do not lead to better outcome.
• With risperidone can get orthostatic hypotension - although, extrapyramidal reactions are less, compared with typical antipsychotics.

Patients should have a named community psychiatric nurse (CPN) who they can contact. Some general practitioners who have a special interest in psychiatry are specially trained and can help CPNs with their caseload.

Monitor the patient, both their physical health, and any symptoms or side effects.
Monitor for drug side effects
This should include regular review looking for the following:

• Abnormal movements (it is good to ask the patient if anyone else has commented on this)
• Any difficulty mobilising or writing (look for bradykinesia)
• Orthostatic hypotension - particularly a problem with chlorpromazine and risperidone
• Blackouts
• Side effects such as weight gain, oligomenorrhoea, sexual dysfunction and itching

EPSEs - extra pyramidal side-effects.

Of course if any abnormality is detected then a full examination should follow with possible referral for investigations and to a specialist for example, arrhythmias require cardiac follow-up.

Monitor for potential drug interactions

• Antipsychotics pose a potential problem for drug interactions. Some examples are antibiotics such as, ciprofloxacin and erythromycin which increase the levels of antipsychotics and carbamazepine which reduces the level. Other interactions occur with antivirals, betablockers, diuretics and sibutramine.
• Sedation will be increased with other sedatives for example, alcohol, and similarly there is increased risk of hypotension with concomitant administration of anti-hypertensives.