Debunking the Myth: Has Stemetil Really Been Discontinued?
The perception that Stemetil (prochlorperazine) has been completely taken off the market is a common misunderstanding stemming from several targeted regulatory actions and commercial decisions. The reality is that while some specific forms of the medication are no longer available, the drug itself, prochlorperazine, remains in use in many countries, including the UK, Australia, and Canada [1.4.1, 1.4.3]. The reasons for the confusion are multifaceted, involving specific product recalls, supply shortages, and a market shift towards generic alternatives.
The Real Reasons Behind Stemetil's Changing Availability
Several key events have fueled the belief that Stemetil is no longer available:
- Discontinuation of Stemetil Syrup: In October 2022, Sanofi discontinued Stemetil Syrup (5 mg/5 ml) in the UK after laboratory tests found excessive levels of an impurity called N-nitrosomethylphenylamine (NMPA) [1.2.1, 1.5.1]. The Medicines and Healthcare products Regulatory Agency (MHRA) issued a recall, classifying NMPA as a probable human carcinogen based on animal studies, making the risk-benefit profile unfavorable for the syrup formulation [1.3.1, 1.3.2]. It is important to note this recall was specific to the liquid form and did not affect Stemetil tablets or injections [1.3.1].
- Cancellation of Suppositories: In Australia, the Stemetil 25mg suppositories were cancelled from the Australian Register of Therapeutic Goods (TGA) in September 2021 by the sponsor, Sanofi-Aventis Australia Pty Ltd [1.2.5].
- Tablet Shortages and Discontinuations: The American Society of Health-System Pharmacists (ASHP) notes that various prochlorperazine maleate tablets have faced shortages due to increased demand or have been discontinued by manufacturers like Viatris [1.2.2, 1.5.4]. Similarly, the TGA in Australia reports current and anticipated shortages of the 5mg tablet blister packs for commercial reasons, though it notes that alternative generic products are available [1.2.7].
- Brand vs. Generic: In many regions, the patent for prochlorperazine has long expired. The brand name Stemetil (or Compazine in the US) is often replaced by cheaper, readily available generic prochlorperazine tablets [1.7.4]. This commercial shift can make the original brand name harder to find.
Understanding Stemetil's Pharmacology
Stemetil's active ingredient, prochlorperazine, is a type of medication known as a phenothiazine. It was originally developed as a 'typical' antipsychotic but is now primarily used at lower doses for its potent anti-nausea (antiemetic) effects [1.6.5, 1.7.4]. It is prescribed for various conditions, including severe nausea and vomiting, vertigo, labyrinthitis, Meniere's disease, and as a short-term treatment for anxiety [1.6.7].
Its primary mechanism of action involves blocking dopamine D2 receptors in a part of the brain called the chemoreceptor trigger zone (CTZ). The CTZ is highly sensitive to chemicals in the blood and, when stimulated, triggers the vomiting center. By blocking dopamine signals in this area, prochlorperazine effectively reduces the sensations of nausea and the urge to vomit [1.6.7]. This pharmacological action, while effective, is also the source of its most significant side effects.
The Significant Risks and Side Effects
The reason prochlorperazine is a prescription-only medicine in most countries lies in its extensive side effect profile [1.4.2]. As a dopamine antagonist, it can interfere with normal motor control, leading to a group of side effects known as extrapyramidal symptoms (EPS).
- Tardive Dyskinesia (TD): A serious, potentially irreversible movement disorder characterized by uncontrollable, repetitive movements of the face, tongue, lips, and limbs [1.6.4, 1.6.5]. The risk increases with long-term use and in older adults [1.6.4].
- Acute Dystonic Reactions: Sudden, involuntary muscle spasms, often affecting the neck, jaw, and eyes [1.6.6].
- Parkinsonism: Symptoms that mimic Parkinson's disease, such as tremor, rigidity, and shuffling walk [1.6.5].
- Neuroleptic Malignant Syndrome (NMS): A rare but life-threatening reaction causing high fever, severe muscle rigidity, altered mental status, and autonomic dysfunction [1.6.1, 1.6.2].
Other common side effects include drowsiness, dizziness, blurred vision, dry mouth, and low blood pressure [1.6.2, 1.6.7].
Comparison of Antiemetic Alternatives
Patients seeking alternatives to Stemetil have several options, each with a different mechanism of action and side effect profile.
| Medication | Drug Class | Primary Use | Key Side Effects |
|---|---|---|---|
| Prochlorperazine (Stemetil) | Phenothiazine / Dopamine Antagonist | Severe nausea, vertigo, psychosis [1.7.4] | Drowsiness, dizziness, movement disorders (EPS, TD) [1.7.4] |
| Ondansetron (Zofran) | Serotonin 5-HT3 Antagonist | Nausea from chemotherapy, radiation, or surgery [1.7.5] | Headache, constipation, diarrhea, potential for QT prolongation [1.7.4] |
| Metoclopramide (Reglan) | Dopamine Antagonist / Prokinetic | Nausea, gastroparesis [1.7.2] | Drowsiness, restlessness, risk of tardive dyskinesia [1.7.2] |
| Cyclizine/Meclizine | Antihistamine | Motion sickness, vertigo-related nausea [1.7.2, 1.7.5] | Drowsiness, dry mouth, blurred vision [1.7.2] |
| Dexamethasone | Corticosteroid | Chemotherapy-induced and postoperative nausea [1.7.5] | Insomnia, agitation, fluid retention (with prolonged use) [1.7.2] |
Conclusion
In conclusion, Stemetil has not been taken off the market on a global scale. The narrative of its disappearance is driven by the very real discontinuation and recall of specific formulations like the syrup and suppositories, ongoing supply chain issues, and a natural market evolution towards generic prochlorperazine [1.2.1, 1.2.5, 1.2.7]. Prochlorperazine remains a potent and clinically relevant medication for severe nausea and other conditions. However, its significant side effect profile, particularly the risk of movement disorders, necessitates careful medical supervision and has contributed to the development and preference for alternative antiemetics in many clinical situations [1.6.4].
For more information on the specific recall of Stemetil syrup, you can refer to the official UK government alert: https://www.gov.uk/drug-device-alerts/class-2-medicines-recall-aventis-pharma-limited-t-slash-a-sanofi-stemetil-5mg-slash-5ml-syrup-el-22-a-slash-41 [1.5.2].
