Stemetil (Prochlorperazine) Injection Dosing
For adults with severe nausea, vomiting, or vertigo when oral therapy is not possible, administer prochlorperazine 12.5 mg intramuscularly or intravenously every 8 hours, or 10 mg intravenously every 4-6 hours as needed.
Standard Dosing Regimens
Intramuscular/Intravenous Administration
- Standard dose: 12.5 mg IM/IV every 8 hours 1
- Alternative dosing: 10 mg IV every 4-6 hours as needed 2, 3
- Intravenous push: 2.5-10 mg IV over 1-2 minutes 4, 5
The evidence supports flexible dosing based on severity. For breakthrough nausea/vomiting in the emergency department, 2.5 mg IV push over 1 minute is highly effective, with mean time to cessation of vomiting of 8.5 minutes 4. This can be repeated after 20 minutes if no response, up to a total of 5 mg 4.
Route-Specific Considerations
Intravenous administration is preferred when rapid symptom control is needed:
- Can be given as slow IV push (1-2 minutes) or diluted for infusion
- No difference in akathisia rates between 2-minute bolus versus 15-minute infusion 6
- Faster onset than intramuscular route (8.5 minutes IV vs 35 minutes IM) 4
Intramuscular administration is appropriate when IV access is unavailable:
- Deep IM injection into large muscle mass
- 12.5-25 mg IM every 6-8 hours 1
Clinical Context-Specific Dosing
For Chemotherapy-Induced Nausea/Vomiting
- Low/minimal emetic risk: 10 mg PO or IV pretreatment, then every 4-6 hours PRN 2
- Breakthrough treatment: 10 mg PO or IV every 4-6 hours, or 25 mg suppository every 12 hours 2
For Pregnancy-Related Nausea (Hyperemesis Gravidarum)
- First-line: 5-10 mg every 6-8 hours PO; 12.5 mg every 8 hours IM/IV; or 25 mg rectally daily 1
- Use lower doses initially and titrate as needed
For Acute Vertigo
- Standard: 5 mg three times daily (oral or IM) 7, 8
- Intramuscular: 85.5% showed clinical improvement with IM administration 7
Special Populations
Elderly or Frail Patients
- Start with lower doses: Use doses in the lower range (e.g., 2.5-5 mg) 9
- Titrate gradually to minimize risk of extrapyramidal symptoms and orthostatic hypotension
Renal/Hepatic Impairment
- Use with caution in renal and hepatic impairment 9
- Consider dose reduction and extended dosing intervals
Critical Safety Considerations
Extrapyramidal Symptoms (EPS)
The most significant concern with prochlorperazine is akathisia and other extrapyramidal reactions:
- Incidence: 14-26% in some studies 6, 10
- Typically occurs within the first week of treatment 10
- Monitor closely for restlessness, agitation, involuntary movements
- Have diphenhydramine 25-50 mg IV/IM available for dystonic reactions 2
Other Adverse Effects
- Sedation and anticholinergic effects are common 9
- Orthostatic hypotension: Monitor blood pressure, especially in elderly 9
- QTc prolongation: Use caution in patients with cardiac risk factors 9
- Parenteral use may cause local irritation at injection site 9
Comparative Effectiveness
Prochlorperazine demonstrates superior efficacy compared to promethazine for uncomplicated nausea/vomiting, with significantly better symptom relief at 30 and 60 minutes (p=0.004 and p<0.001) and fewer treatment failures (9.5% vs 31%) 11. However, it causes significantly less sedation than promethazine (38% vs 71%, p=0.002) 11.
For vertigo specifically, promethazine may be more effective at reducing vertigo symptoms, though prochlorperazine causes fewer side effects overall 12.
Administration Technique
- IV push: Administer slowly over 1-2 minutes to minimize adverse effects
- IM injection: Deep injection into large muscle mass (upper outer quadrant of gluteus maximus or lateral thigh)
- Avoid intra-arterial administration
- Can be diluted in 50 mL normal saline for 15-minute infusion if preferred, though this does not reduce akathisia risk 6
Duration of Therapy
Continue treatment for 2 days after signs and symptoms of nausea/vomiting have resolved, though longer therapy may be required in complicated cases. For acute vertigo, typical treatment duration is 5-7 days 7, 8.