When Your Pharmacy Can't Fill Compro, You Still Have Options

If you rely on Compro (Prochlorperazine 25 mg suppositories) for severe nausea and vomiting and your pharmacy tells you it's out of stock, the frustration is real. But the good news is that there are several effective alternatives your doctor can consider switching you to — some in the same drug class, and others that work through different mechanisms.

This guide walks you through the most common alternatives to Compro, how they compare, and what to discuss with your healthcare provider.

What Is Compro and How Does It Work?

Compro contains Prochlorperazine, a first-generation antipsychotic in the phenothiazine drug class. It's FDA-approved for the control of severe nausea and vomiting in adults and is available as a 25 mg rectal suppository.

Prochlorperazine works by blocking D2 dopamine receptors in the brain's chemoreceptor trigger zone (CTZ) — the area responsible for triggering the vomiting reflex. By dampening signals in the CTZ, it helps reduce nausea and prevent vomiting. It also has some antihistaminic and anticholinergic activity, which contributes to its sedating and anti-nausea effects.

The suppository form is particularly useful for patients who can't keep oral medications down — which is often the whole reason they need an antiemetic in the first place. For more on how Compro works, see our detailed explainer on Compro's mechanism of action.

Alternative 1: Ondansetron (Zofran)

Ondansetron is one of the most widely prescribed antiemetics in the United States. It belongs to a different drug class — the 5-HT3 receptor antagonists — which means it works by blocking serotonin receptors rather than dopamine receptors.

Key facts about Ondansetron:

• Available forms: Oral tablets, orally disintegrating tablets (ODT), oral solution, and injectable
• Typical dose: 4 to 8 mg every 8 hours as needed
• Pros: Widely available, fewer sedation and movement-related side effects (no risk of tardive dyskinesia), comes in an ODT form that dissolves on the tongue (useful when vomiting)
• Cons: Can cause headache, constipation, and in rare cases QT prolongation; may not be as effective for some patients as dopamine-blocking antiemetics
• Cost: Generic ondansetron is very affordable — as low as $4 to $10 for 12 tablets with a coupon

Ondansetron is often a first-choice alternative because of its favorable side effect profile and wide availability. The orally disintegrating tablet is a practical option for patients who can't swallow pills due to nausea.

Alternative 2: Promethazine (Phenergan)

Promethazine is in the same phenothiazine class as Prochlorperazine. It works through similar mechanisms — blocking dopamine, histamine, and acetylcholine receptors — making it effective for nausea, vomiting, motion sickness, and as a sedative.

Key facts about Promethazine:

• Available forms: Oral tablets (12.5 mg, 25 mg, 50 mg), rectal suppositories (12.5 mg, 25 mg), injectable, and oral syrup
• Typical dose: 12.5 to 25 mg every 4 to 6 hours as needed
• Pros: Available as a suppository (good replacement if you specifically need a rectal formulation), widely stocked at pharmacies, inexpensive generic
• Cons: More sedating than Prochlorperazine, carries similar risks of extrapyramidal symptoms and tardive dyskinesia, boxed warning about tissue injury with IV use
• Cost: Generic promethazine tablets cost as low as $3 to $8 for 12 tablets with a coupon; suppositories around $15 to $40

If you specifically need a suppository formulation, Promethazine suppositories are often more readily available than Compro and are a close pharmacological match.

Alternative 3: Metoclopramide (Reglan)

Metoclopramide is a dopamine antagonist and prokinetic agent. It works by blocking dopamine receptors (similar to Prochlorperazine) and also enhances gastric motility — meaning it helps the stomach empty faster, which can reduce nausea.

Key facts about Metoclopramide:

• Available forms: Oral tablets (5 mg, 10 mg), oral solution, injectable
• Typical dose: 10 mg up to four times daily, 30 minutes before meals
• Pros: Dual mechanism (antiemetic + prokinetic), widely available, generic is inexpensive
• Cons: Carries an FDA boxed warning for tardive dyskinesia with prolonged use (more than 12 weeks), can cause drowsiness, restlessness, and diarrhea
• Cost: Generic metoclopramide is very affordable — around $4 to $12 for 30 tablets with a coupon

Metoclopramide is a good option for patients whose nausea is related to gastroparesis (delayed stomach emptying) or other gastric motility issues, since it addresses both the nausea and the underlying cause.

Alternative 4: Granisetron (Kytril)

Granisetron is another 5-HT3 receptor antagonist, similar to Ondansetron but sometimes preferred for specific situations like chemotherapy-induced nausea and vomiting (CINV).

Key facts about Granisetron:

• Available forms: Oral tablets (1 mg), injectable, and transdermal patch (Sancuso)
• Typical dose: 1 mg twice daily or 2 mg once daily for chemotherapy-related nausea
• Pros: Effective for chemotherapy- and radiation-induced nausea, transdermal patch option provides continuous delivery for up to 7 days
• Cons: More expensive than Ondansetron, primarily indicated for chemotherapy/radiation settings, may require prior authorization for insurance coverage
• Cost: Generic granisetron tablets around $15 to $40; transdermal patch significantly more expensive

Granisetron is most relevant if your nausea is related to cancer treatment. For general-purpose antiemetic use, Ondansetron is usually preferred due to lower cost and wider availability.

How to Switch: What to Tell Your Doctor

If you can't find Compro and need to switch to an alternative, here's what to discuss with your healthcare provider:

• Why you need the suppository form: If you can't tolerate oral medications due to vomiting, make sure your doctor knows this so they can prescribe an appropriate formulation (Promethazine suppositories, Ondansetron ODT, or injectable options).
• Your medical history: Some alternatives have specific risks. For example, Metoclopramide should be used cautiously if you have a history of movement disorders, and Ondansetron requires caution if you have cardiac rhythm issues.
• Duration of treatment: If you need ongoing antiemetic therapy, your doctor should consider long-term safety profiles. Metoclopramide, for instance, has limits on duration of use.
• Cost concerns: Let your doctor know if cost is a factor. Most alternatives are affordable generics, but some formulations (like the Granisetron patch) can be expensive.

Final Thoughts

Not being able to fill your Compro prescription is stressful, especially when you're dealing with severe nausea. But you're not stuck. Ondansetron, Promethazine, Metoclopramide, and Granisetron all offer effective nausea and vomiting relief, each with their own strengths.

Talk to your doctor about which alternative is best for your specific situation. And before switching, check whether Compro might be available at another pharmacy near you using Medfinder. For the latest on Compro availability, visit our Compro shortage update. And for information on reducing costs on any of these medications, see how to save money on Compro.