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Phenergan (Promethazine) for Dogs
Promethazine (Phenergan) is a phenothiazine antihistamine with antiemetic + significant sedation.
Dose
0.5-1 mg/kg PO every 8-12 hours
Dose Reference Table
| Weight | Range |
|---|---|
| 5 kg | 2.5-5 mg |
| 10 kg | 5-10 mg |
| 20 kg | 10-20 mg |
| 30 kg | 15-30 mg |
| 40 kg | 20-40 mg |
Tablets: 12.5, 25, 50 mg. Suppositories + injectable available.
Indications (Limited Modern Use)
- Motion sickness (30-60 min before travel)
- Mild sedation pre-procedure
- Nausea/vomiting (Cerenia better)
- Allergic reactions
Modern Alternatives Preferred
| Use | Preferred |
|---|---|
| Vomiting | Cerenia (maropitant) 1-2 mg/kg q24h |
| Motion sickness | Dimenhydrinate 4-8 mg/kg q8h; meclizine 4-8 mg/kg q24h |
| Sedation | Acepromazine 0.5-2 mg/kg |
| Anxiety | Trazodone 4-12 mg/kg; gabapentin |
Side Effects
- Significant sedation (expected)
- Hypotension (phenothiazine)
- Anticholinergic (dry mouth, urinary retention)
- Constipation
- Mild lowered seizure threshold
⚠ Avoid
- Glaucoma
- Seizure disorder (caution)
- Severe hypotension
- Severe cardiac disease
- Concurrent MAOI
Frequently Asked Questions
How much Phenergan for my dog?
DOSE: 0.5-1 mg/kg PO every 8-12 hours. EXAMPLES: 1) 5 kg = 2.5-5 mg; 2) 10 kg = 5-10 mg; 3) 20 kg = 10-20 mg; 4) 30 kg = 15-30 mg; 5) 40 kg = 20-40 mg. TABLETS 12.5, 25, 50 mg; SUPPOSITORIES; INJECTABLE 25, 50 mg/mL. For motion sickness, give 30-60 min BEFORE travel. CERENIA (maropitant) PREFERRED for most vomiting in modern practice. Significant sedation expected. AVOID in glaucoma.
Can I give my dog Phenergan for motion sickness?
YES but BETTER ALTERNATIVES exist. Phenergan works but has significant sedation + side effects. BETTER MOTION SICKNESS options: 1) CERENIA (maropitant) 1-2 mg/kg PO q24h – superior anti-nausea, less sedation; FDA-approved for motion sickness in dogs; 2) DIMENHYDRINATE (Dramamine) 4-8 mg/kg q8h – traditional, OTC; 3) MECLIZINE (Bonine) 4-8 mg/kg q24h – longer-acting; 4) BENADRYL 1-2 mg/kg q8-12h – mild antiemetic, more sedating; 5) Phenergan adjunct if others fail. PROTOCOL: 1) Give 30-60 min before travel; 2) Withhold food 2-4 hours before; 3) Cool environment; 4) Familiarize dog with car gradually; 5) Anti-anxiety adjunct (trazodone) if needed; 6) Short trips first to acclimate. SIGNS of motion sickness: drooling, lip-licking, vomiting, restlessness, lethargy. Cerenia generally preferred over Phenergan due to better efficacy + safety + targeted action.
Is Phenergan safe for my dog long-term?
SHORT-TERM ACUTE use generally safe; LONG-TERM use NOT recommended. CONCERNS with chronic Phenergan: 1) Cumulative SEDATION; 2) Anticholinergic effects long-term; 3) Hepatic enzyme elevation possible; 4) Behavioral changes; 5) Constipation chronic; 6) Limited efficacy long-term. SHORT-TERM situations (acceptable): 1) Single travel events; 2) Pre-procedure sedation; 3) Acute motion sickness; 4) Acute allergic reaction; 5) Limited duration <7 days. CHRONIC use considerations – use alternatives: 1) Chronic atopy – Apoquel, Cytopoint; 2) Chronic anxiety – SSRIs (fluoxetine), trazodone, gabapentin; 3) Chronic nausea – Cerenia (maropitant) can be used long-term; 4) Chronic motion sickness – investigate underlying cause; consider behavioral modification + Cerenia. WHEN PHENERGAN STILL HAS PLACE: 1) Patient does well on it short-term; 2) Cost considerations; 3) Specific indication; 4) Vet preference; 5) Combined with other treatments. CONTRAINDICATIONS chronic: 1) Glaucoma; 2) Seizure disorder; 3) Cardiac disease; 4) Senior with multiple comorbidities. Discuss with vet for appropriate use + duration.
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References & Further Reading
The dosing ranges and safety information on this page are drawn from the following veterinary references. Always defer to your own veterinarian and the manufacturer’s label for your specific product.
- Plumb DC. Promethazine.
- Rangel-Lopez A et al. Anti-emetic options in veterinary medicine.
- Boscan P et al. Maropitant superior to other anti-emetics.
- PuppaDogs. Cerenia Calculator, Dimenhydrinate Calculator, Meclizine Calculator. puppadogs.com.
⚕️ Medical Disclaimer
The information on this page is intended for educational purposes only and does not replace a hands-on veterinary examination. Drug doses depend on your dog’s complete clinical picture, concurrent medications, and the exact product formulation. Always confirm dosing with your veterinarian before administering any medication, and contact a 24-hour veterinary emergency service or animal poison control immediately if you suspect a medication overdose or adverse reaction. Editorial standards: every drug dose published on PuppaDogs is cross-checked against multiple authoritative veterinary references and reviewed by PuppaDogs Veterinary Editorial Team before publication.
