What is the recommended PRN (as needed) dose of Nozinan (methotrimeprazine) for an elderly patient with a psychiatric condition or dementia?

Nozinan (Methotrimeprazine) PRN Dosing for Elderly Patients

For elderly patients with delirium who are unable to swallow, levomepromazine (Nozinan/methotrimeprazine) should be initiated at 6.25-12.5 mg subcutaneously as a starting dose, then hourly as required, with maintenance via subcutaneous infusion of 50-200 mg over 24 hours. 1

Initial PRN Dosing Strategy

For elderly or debilitated patients specifically:

• Starting dose: 6.25-12.5 mg subcutaneously (half the standard adult dose) 1
• Frequency: Hourly as required for acute agitation or delirium 1
• Standard adult dose: 12.5-25 mg subcutaneously for comparison 1

The reduced starting dose for elderly patients is critical because this population experiences substantially higher rates of adverse effects including hypotension, sedation, and extrapyramidal symptoms with phenothiazines. 1

Maintenance Dosing

If PRN dosing is needed frequently (more than twice daily):

• Transition to continuous subcutaneous infusion: 50-200 mg over 24 hours 1
• Doses exceeding 100 mg over 24 hours require specialist supervision 1
• Titrate according to response while monitoring for excessive sedation and cardiovascular effects 1

Clinical Context and Appropriate Use

Levomepromazine is specifically indicated for:

• Delirium with agitation in patients unable to swallow 1
• Severe agitation when benzodiazepines alone are insufficient 1
• Can be combined with midazolam if anxiety is also present 1

This medication should NOT be used for:

• Nonpsychotic depression, anxiety disorders, or simple irritability without a major psychiatric syndrome 2
• First-line treatment of agitated dementia without psychotic features 1, 2

Critical Safety Considerations

Before initiating levomepromazine, address reversible causes:

• Hypoxia, urinary retention, constipation, pain 1
• Medication-induced delirium (anticholinergics, benzodiazepines) 1
• Metabolic disturbances 1

Monitoring requirements:

• Blood pressure (risk of orthostatic hypotension, especially with initial doses) 1
• Level of sedation (levomepromazine is highly sedating) 1
• Extrapyramidal symptoms, though less common than with high-potency antipsychotics 1
• QTc prolongation risk 2

Duration of Treatment

For delirium: Taper within 1 week after resolution of acute symptoms 2

For agitated dementia: If antipsychotic is necessary, attempt to taper within 3-6 months to determine the lowest effective maintenance dose, as prolonged use increases risk of cerebrovascular events and mortality in elderly patients with dementia 1, 2

Common Pitfalls to Avoid

• Do not use standing doses without attempting PRN dosing first - PRN administration allows assessment of actual need and minimizes cumulative exposure 3
• Do not prescribe without specific behavioral targets - orders must include definitive descriptions of target behaviors (e.g., "physical aggression toward staff," not simply "agitation") 3
• Do not exceed maximum daily doses - cumulative PRN doses should not exceed 200 mg/24 hours without specialist input 1
• Do not combine with other QTc-prolonging medications without careful monitoring 2
• Avoid in patients with Parkinson's disease - use quetiapine instead if antipsychotic is absolutely necessary 2

Alternative Approaches

If levomepromazine is unavailable or contraindicated, consider:

• Haloperidol 0.5-1 mg subcutaneously for delirium in elderly patients (maximum 5 mg daily) 1
• Quetiapine 12.5-25 mg orally if patient can swallow (more sedating, lower EPS risk) 1
• Risperidone 0.25-0.5 mg for agitated dementia with psychotic features 1, 2