Compro Drug Interactions: A Complete Guide

Compro (Prochlorperazine) is effective at treating severe nausea and vomiting, but it interacts with a significant number of other medications. Some of these interactions can be dangerous.

Whether you've just been prescribed Compro or you're already taking it and starting a new medication, this guide covers the interactions you need to know about — and what to tell your doctor to stay safe.

How Drug Interactions Work with Compro

Compro is a phenothiazine that blocks multiple types of receptors in the brain: dopamine, histamine, cholinergic, and noradrenergic. This broad activity is what makes it effective — but it's also why it interacts with so many other drugs.

Drug interactions with Compro generally happen in three ways:

1. Additive effects — Another drug does something similar to Compro, and the combined effect becomes too strong (e.g., two sedating medications causing excessive drowsiness).
2. Opposing effects — Another drug works in the opposite direction, making one or both medications less effective (e.g., dopamine agonists vs. Compro's dopamine blocking).
3. Metabolism changes — A drug affects how your liver processes Compro, leading to higher or lower levels in your blood than expected.

Major Drug Interactions

These interactions carry the highest risk and may require your doctor to choose a different medication or closely monitor you:

CNS Depressants

Opioids (Oxycodone, Hydrocodone, Morphine, Fentanyl, Tramadol), benzodiazepines (Xanax/Alprazolam, Ativan/Lorazepam, Valium/Diazepam, Klonopin/Clonazepam), and barbiturates (Phenobarbital) all increase sedation when combined with Compro. This combination can cause:

• Excessive drowsiness and difficulty staying awake
• Slowed breathing (respiratory depression)
• Dangerously low blood pressure
• Impaired coordination and increased fall risk

This is one of the most important interactions because opioids are commonly prescribed for pain, and many patients on opioids also need an antiemetic for opioid-induced nausea.

Anticholinergic Medications

Drugs with anticholinergic properties — Scopolamine, Atropine, Diphenhydramine (Benadryl), Oxybutynin (Ditropan), and many older antihistamines — can cause additive anticholinergic effects when combined with Compro:

• Severe dry mouth
• Urinary retention
• Severe constipation
• Confusion and delirium (especially in elderly patients)
• Overheating (impaired sweating)

Propranolol (Inderal)

Taking Propranolol with Prochlorperazine can increase the blood levels of both drugs, potentially leading to excessive blood pressure lowering, increased sedation, and higher risk of side effects from each medication.

Anticonvulsants

Prochlorperazine lowers the seizure threshold, which can counteract seizure medications like Phenytoin (Dilantin), Carbamazepine (Tegretol), Valproic Acid (Depakote), and Levetiracetam (Keppra). Your doctor may need to adjust your anticonvulsant dose. Additionally, Phenytoin metabolism can be altered by Prochlorperazine, potentially leading to Phenytoin toxicity.

QT-Prolonging Drugs

Compro can prolong the QTc interval on an EKG, which increases the risk of dangerous heart rhythm abnormalities. Other medications that also prolong QT include:

• Antiarrhythmics: Amiodarone, Sotalol, Dofetilide
• Antibiotics: Azithromycin (Z-Pack), Fluoroquinolones (Levofloxacin, Ciprofloxacin)
• Antifungals: Fluconazole
• Antipsychotics: Haloperidol, Ziprasidone
• Antidepressants: Citalopram, Escitalopram

Combining two or more QT-prolonging drugs significantly increases the risk of a potentially fatal arrhythmia called Torsades de Pointes.

Moderate Drug Interactions

These interactions are less immediately dangerous but still important:

• Guanethidine and related antihypertensives — Compro may counteract their blood-pressure-lowering effects, making your blood pressure harder to control.
• Thiazide diuretics (Hydrochlorothiazide) — May worsen orthostatic hypotension (dizziness when standing) when combined with Compro.
• Oral anticoagulants (Warfarin/Coumadin) — Phenothiazines like Compro can reduce the effectiveness of blood thinners. Your doctor may need to monitor your INR more closely.
• Levodopa and dopamine agonists (Carbidopa-Levodopa/Sinemet, Pramipexole/Mirapex, Ropinirole/Requip) — Since Compro blocks dopamine receptors, it directly opposes these Parkinson's disease medications. This combination should generally be avoided.

Supplements and OTC Medications to Watch

Don't forget about over-the-counter products and supplements:

• Diphenhydramine (Benadryl) — Anticholinergic and sedative effects add to Compro's. Avoid using them together without asking your doctor.
• Doxylamine (Unisom) — Another sedating antihistamine that increases drowsiness.
• Sleep aids containing antihistamines (ZzzQuil, Tylenol PM) — These contain Diphenhydramine and can cause excessive sedation with Compro.
• Melatonin — Generally safe, but may add to drowsiness.
• St. John's Wort — Can affect the metabolism of many drugs. Discuss with your doctor.
• Kava and Valerian root — Both have sedative properties that may be enhanced by Compro.

Food and Drink Interactions

• Alcohol — This is a major one. Alcohol combined with Compro causes enhanced CNS depression, leading to excessive sedation, impaired judgment, slowed breathing, and dangerous drops in blood pressure. Avoid alcohol completely while taking Compro.
• Grapefruit juice — May affect how your liver metabolizes Prochlorperazine through CYP enzyme pathways. Avoid grapefruit juice or discuss with your doctor.

What to Tell Your Doctor

Before starting Compro, give your doctor a complete picture:

1. A full medication list — Include all prescription drugs, OTC medications, and supplements. Don't forget things you take occasionally (sleep aids, allergy pills, pain relievers).
2. Your medical history — Especially any history of seizures, heart rhythm problems, liver disease, Parkinson's disease, or glaucoma.
3. Alcohol use — Be honest about how much you drink. This matters for safety.
4. Other prescribers — If you see multiple doctors (e.g., a psychiatrist and a primary care doctor), make sure each one knows what the others have prescribed.
5. Pharmacy — Using one pharmacy for all your medications helps the pharmacist catch potential interactions.

If you're ever unsure about whether a new medication is safe to take with Compro, call your pharmacist. They are drug interaction experts and can give you a quick answer.

Final Thoughts

Compro is an effective antiemetic, but its broad receptor activity means it interacts with a wide range of medications. The most critical interactions involve CNS depressants (opioids, benzodiazepines), QT-prolonging drugs, and medications that oppose its dopamine-blocking mechanism.

Always keep your healthcare team informed about everything you're taking, and don't hesitate to ask questions. For more on Compro, check out our guides on side effects and uses and dosage.