Does Compazine Cause Drowsiness?
Yes, Compazine (prochlorperazine) does cause drowsiness as a recognized adverse effect, though it occurs less frequently than other side effects like extrapyramidal symptoms.
Documented Drowsiness Rates
The FDA drug label explicitly warns that prochlorperazine may impair mental and/or physical abilities, especially during the first few days of therapy, and cautions patients about activities requiring alertness such as operating vehicles or machinery 1. This is a clear acknowledgment that sedation and drowsiness are expected effects.
In clinical studies, drowsiness occurs with the following frequency:
- Multiple-dose regimens: Drowsiness affects approximately 10% (95% CI 5-21%) of patients 2
- High-dose studies: In one study using 30-40 mg doses for chemotherapy-induced nausea, drowsiness occurred in 12 out of 82 treatment cycles 3
- Comparative studies: Drowsiness was reported as a side effect in 11% of patients receiving prochlorperazine, which was statistically less than the 23% seen with cinnarizine 4
Clinical Context and Severity
Drowsiness from prochlorperazine is generally moderate and less problematic than its extrapyramidal side effects, which are the more concerning adverse reactions 5. The American Family Physician guidelines list multiple serious adverse effects of prochlorperazine including hypotension, tachycardia, akathisia, pseudo-parkinsonism, tardive dyskinesia, and dystonia, with drowsiness mentioned alongside these 5.
Important Safety Considerations
- Falls risk: The FDA label specifically warns that prochlorperazine may cause somnolence, postural hypotension, and motor instability, which may lead to falls and consequently fractures or other injuries 1
- Drug interactions: Phenothiazines like prochlorperazine may intensify or prolong the action of central nervous system depressants including alcohol, anesthetics, and narcotics 1
- Timing: Drowsiness is particularly prominent during the first few days of therapy 1
Practical Implications
When prescribing prochlorperazine, counsel patients that:
- Drowsiness is expected in approximately 1 in 10 patients receiving standard doses 2
- Avoid driving or operating machinery until they know how the medication affects them 1
- Avoid alcohol and other CNS depressants which can potentiate sedation 1
- Fall precautions should be implemented, especially in elderly patients or those with mobility issues 1
The sedating properties of prochlorperazine are sometimes therapeutically useful—for example, the NCCN Palliative Care Guidelines note that chlorpromazine (a related phenothiazine) can be used for refractory insomnia in dying patients, suggesting the sedative effects of this drug class can be beneficial in certain contexts 5.