prochlorperazine
Meaning of prochlorperazine: Blocking dopamine in the brainstem area that triggers vomiting also explains the stiffness and restlessness this drug can cause.
Definition of prochlorperazine
Prochlorperazine is a phenothiazine medication used mainly to control nausea and vomiting. It blocks dopamine receptors in the brainstem region that triggers the vomiting reflex, quieting the signals that would otherwise produce sickness. At higher doses the same dopamine blockade acts more widely in the brain, and the drug is also approved for certain psychotic illnesses and short term anxiety.
What is it used for?
Nausea and vomiting are the main target, whatever the source: migraine, disorders of the inner ear such as vertigo, motion sickness, the hours after an operation, and sickness caused by chemotherapy or radiation. Because the drug also quiets signals coming from the balance organs, it eases the dizziness that usually travels with the nausea rather than treating the two separately. It can be swallowed, dissolved between the lip and gum, given as a suppository, or injected, a range that matters when vomiting makes a tablet pointless. At higher doses it has long been approved for schizophrenia and for severe anxiety over short periods, a legacy of the phenothiazine family it belongs to, although newer antipsychotic medicines have taken over most of that work.
Why can it cause movement problems?
Dopamine does far more than register nausea. The same receptors sit in the brain circuits that smooth and coordinate movement, and blocking them there produces effects familiar from antipsychotic treatment. Muscles of the neck, jaw, tongue or eyes can pull into a sustained spasm within hours of a first dose, a frightening but treatable reaction that is most common in younger patients. A relentless inner restlessness, called akathisia, is often mistaken for the anxiety of being unwell. Repetitive involuntary movements of the face and tongue can follow prolonged use and may persist. Drowsiness, dry mouth and blurred vision come instead from the drug's weaker effects on histamine and acetylcholine signaling.
How does it compare with other antinausea drugs?
| Class | Signal it blocks | Where it is usually chosen |
|---|---|---|
| Phenothiazines such as prochlorperazine | Dopamine | Migraine, vertigo, general nausea and vomiting |
| Serotonin blockers | Serotonin | Chemotherapy, radiation and the period after surgery |
| Antihistamines | Histamine | Motion sickness and inner ear causes |
| Substance P blockers | Substance P | Delayed sickness in the days after chemotherapy |
No single antiemetic suits every cause, because the vomiting reflex can be set off through several separate signaling routes. Drugs are matched to the likely trigger and combined when one alone is not enough, which is why prochlorperazine often appears alongside a second agent rather than on its own.
Also known as
Used in a sentence
Prochlorperazine was administered to control the patient's nausea and vomiting during the migraine episode.
Good to know
Prochlorperazine can produce movement related side effects similar to those seen with antipsychotic medications, a consequence of its dopamine blocking action that is sometimes overlooked when the drug is used only for nausea.