Apomorphine Drug Interactions: What to Avoid and What to Tell Your Doctor

Apomorphine has some of the most clinically significant drug interactions in all of Parkinson's medicine. One combination—apomorphine with ondansetron (Zofran)—is absolutely contraindicated and has caused deaths. Every patient on apomorphine, and every caregiver, needs to understand these interactions before starting treatment and every time a new medication is added to the regimen.

CONTRAINDICATED (Never Combine): 5-HT3 Antagonists

This is the most important drug interaction for every apomorphine patient to know.

5-HT3 antagonists are a class of anti-nausea medications commonly given in hospitals, chemotherapy clinics, and surgical settings. They include:

Ondansetron (Zofran) — the most commonly encountered

Granisetron (Kytril)

Dolasetron (Anzemet)

Palonosetron (Aloxi)

Alosetron (Lotronex)

Taking any of these with apomorphine can cause profound hypotension (dangerously low blood pressure) and sudden loss of consciousness. This interaction is not merely a caution—it is a hard contraindication. If you are given ondansetron during a hospital stay, surgical procedure, or chemotherapy, tell the medical team immediately that you take apomorphine.

The reason for this interaction is not fully understood, but it may involve an interaction between the serotonin system and apomorphine's vascular effects. Whatever the mechanism, the clinical consequence is severe and the combination should never be used.

MAJOR Interactions: Drugs That Significantly Increase Risk

The following interactions are serious and require careful physician oversight:

Antihypertensives and vasodilators: Apomorphine already lowers blood pressure. Combining it with blood pressure-lowering drugs (ACE inhibitors, calcium channel blockers, alpha-blockers, diuretics) can cause severe, symptomatic hypotension. Your doctor may need to adjust your blood pressure medications when starting apomorphine.

Antipsychotics and dopamine antagonists: Haloperidol, chlorpromazine, metoclopramide, and other dopamine-blocking drugs directly antagonize apomorphine's mechanism of action—reducing its effectiveness. They can also worsen Parkinson's symptoms. Many antipsychotics are inappropriate for Parkinson's patients and should be avoided entirely.

QTc-prolonging drugs: Apomorphine prolongs the heart's QTc interval, increasing the risk of a dangerous arrhythmia called Torsades de pointes. Many common drugs also prolong QTc—including some antibiotics (azithromycin, fluoroquinolones), antidepressants (tricyclics, some SSRIs), and antiarrhythmics. Combining these with apomorphine increases arrhythmia risk. Your doctor should review your full medication list for QTc risk.

MODERATE Interactions: Use With Caution

CNS depressants and alcohol: Sedatives, opioids, antihistamines, muscle relaxants, benzodiazepines, and alcohol can all add to apomorphine's sedating effects. This increases the risk of falls, sleep attacks, and poor coordination. Avoid alcohol entirely while on apomorphine.

Other dopamine agonists: Adding apomorphine to existing dopamine agonists (pramipexole, ropinirole, rotigotine) requires careful dose management. Combined dopaminergic effects can worsen dyskinesia, impulse control problems, and hypotension.

Foods and Substances to Avoid

Alcohol: Do not drink alcohol while taking apomorphine. It worsens dizziness, hypotension, sedation, and fall risk.

Sulfite sensitivity: Apomorphine injection contains sodium metabisulfite, a sulfite preservative. Patients with sulfite sensitivity or asthma may experience allergic reactions or bronchospasm.

What to Tell Your Doctor and Pharmacist Before Starting Apomorphine

Provide a complete medication list, including:

All prescription medications, including OTC drugs and supplements

Any history of anti-nausea medications prescribed in the past (especially 5-HT3 antagonists)

Heart conditions or a known history of QT prolongation

Asthma or sulfite allergy

Blood pressure medications

Always carry a card in your wallet stating that you take apomorphine and cannot receive 5-HT3 antagonists. This is critical for emergency situations where you may not be able to communicate this information yourself.

See also our guide on apomorphine side effects to understand the full clinical profile of this medication.

Need help locating apomorphine? medfinder calls pharmacies near you to check which ones have your medication in stock.