Is Seroquel (quetiapine) suitable as a pro re nata (PRN) medication?

Quetiapine (Seroquel) as PRN Medication

Quetiapine can be used as a PRN medication for acute agitation and delirium, with a recommended starting dose of 25 mg orally as needed, though it is not a first-line choice compared to lorazepam or haloperidol for acute agitation. 1, 2

Clinical Context and Positioning

Quetiapine is listed in established guidelines as an option for PRN use, but with important caveats about its role in the treatment hierarchy:

• For acute agitation and psychosis, lorazepam (1-2 mg) is the preferred first-line PRN agent due to its rapid onset and favorable safety profile, with haloperidol (0.5-5 mg IM) or olanzapine (2.5-10 mg) as alternative first-line antipsychotic options 2
• Quetiapine is positioned as a second-generation antipsychotic option for PRN use specifically in delirium management in cancer patients, but not as the primary choice 1

PRN Dosing Protocol

When quetiapine is selected for PRN use:

• Starting dose: 25 mg orally (immediate release) as needed 1
• Scheduled dosing if required: 25 mg every 12 hours 1
• Reduce dose in older patients and those with hepatic impairment 1
• Oral route only - quetiapine cannot be given intramuscularly or intravenously, which limits its utility in severely agitated patients who cannot take oral medications 1

Key Advantages of Quetiapine

• Sedating properties make it useful for agitation with insomnia 1
• Lower risk of extrapyramidal symptoms (EPS) compared to typical antipsychotics and some other atypical agents 1, 3, 4, 5
• Does not elevate prolactin levels at therapeutic doses 4, 5
• Placebo-level incidence of EPS across entire dose range 5

Critical Limitations and Safety Concerns

Route restriction: Quetiapine's oral-only administration is a major limitation for PRN use in severely agitated or uncooperative patients who cannot safely take oral medications 1

Adverse effects to monitor:

• Sedation (can be excessive) 1
• Orthostatic hypotension and dizziness 1
• Increased fall risk, particularly in elderly or frail patients 2
• Metabolic effects with long-term use 6

Abuse potential: Case reports document quetiapine abuse and dependence, particularly in prisoners and patients with substance use disorders, where it is sometimes used intranasally or intravenously (off-label routes) or combined with other substances for sedative effects 7

Clinical Decision Algorithm for PRN Antipsychotic Selection

For cooperative patients with mild-moderate agitation:

• First choice: Oral lorazepam 1 mg PRN 2
• Alternative: Oral quetiapine 25 mg PRN (if sedation desired and patient can tolerate oral route) 1

For uncooperative or severe agitation:

• First choice: IM/IV lorazepam 1-2 mg or IM haloperidol 2-5 mg 2
• Quetiapine is NOT appropriate (no parenteral formulation) 1

For delirium in cancer patients with perceptual disturbances:

• Consider quetiapine 25 mg PO PRN as one option among several antipsychotics 1
• Use lowest effective dose for shortest duration 1

For patients requiring both agitation control and treatment of underlying psychosis:

• Olanzapine 2.5-5 mg PO/SC/IM PRN is preferred over quetiapine due to multiple route options 2, 6

Common Pitfalls to Avoid

• Do not use quetiapine as first-line PRN when faster-acting agents with parenteral options are available 2
• Do not prescribe quetiapine PRN for patients who may become unable to take oral medications during agitation episodes 1
• Avoid in patients with substance use disorders given abuse potential 7
• Use extreme caution in elderly patients - start with lower doses and monitor closely for falls and orthostatic hypotension 1, 2