Promethazine
Also known as: Phenergan, Phenadoz, Promethegan
Promethazine is used to help control nausea and vomiting, or occasionally to treat allergic reactions. * **Dry Mouth**: This medication can cause a dry mouth. You can relieve this by applying small amounts of water to your pet's tongue for 10-15 minutes. * **Sedation**: It may cause drowsiness, sedation, or mild behavior changes. Contact your veterinarian if these effects are severe or concerning. * **When to Call the Vet**: Protracted vomiting or diarrhea can be serious; contact your veterinarian if your pet's clinical signs do not improve. * **Warning Signs**: Immediately contact your veterinarian if your animal exhibits abnormal, jerky movements, tremors, or becomes rigid.
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
What it is used for
- As an antiemetic
- As an antihistamine
- As an antihistamine
- As an antiemetic
- As an antihistamine
- As an antihistamine
How it is given
Possible side effects
- Sedation or lethargy
- Anticholinergic effects (dry mouth, urinary retention, decreased GI motility)
- Hypotension (especially with rapid IV administration or in hypovolemic patients)
- Extrapyramidal signs (tremors, rigidity, torticollis) - rare but possible
- Sedation / Lethargy
- Dry mucous membranes (anticholinergic effect)
- Tachycardia
- Hypotension
- Paradoxical excitation (especially in cats)
- Gastrointestinal disturbances
Cautions & contraindications
- Hypovolemia or shock (due to hypotensive effects)
- Tetanus or strychnine intoxication (due to extrapyramidal effects)
- Human label black box warning: Contraindicated in children < 2 years old (fatal respiratory depression)
- Known hypersensitivity to phenothiazines
- Severe central nervous system depression
- Comatose patients
- Use with caution in patients with seizure disorders
- Use with caution in patients with severe hepatic or cardiovascular disease
- Use cautiously and at smaller doses in animals with **hepatic dysfunction**, **cardiac disease**, or general debilitation. Animals may require lower dosages of general anesthetics following phenothiazine administration. Use with extreme caution in very young or severely debilitated animals. Promethazine can cause false-positive results for salicylates in urine and false-positive/negative results for chorionic gonadotropin in urine.
Drug interactions
- Antacids: May cause reduced GI absorption of oral phenothiazines.
- Antidiarrheal mixtures (e.g., Kaolin/pectin, bismuth subsalicylate): May cause reduced GI absorption of oral phenothiazines.
- Atropine & other anticholinergics: May have additive anticholinergic effects when used with promethazine.
- CNS Depressant Agents (barbiturates, narcotics, anesthetics): May cause additive CNS depression if used with phenothiazines.
- Epinephrine: Phenothiazines block alpha-adrenergic receptors; concomitant epinephrine can lead to unopposed beta-activity causing vasodilation and increased cardiac rate (epinephrine reversal).
- Metoclopramide: Phenothiazines may potentiate the extrapyramidal effects of metoclopramide.
- Monoamine Oxidase Inhibitors (MAOIs): May potentiate extrapyramidal effects.
- Opiates: May enhance the hypotensive effects of phenothiazines; dosages may need to be reduced.
- Organophosphate Agents: Phenothiazines should not be given within one month of worming with these agents as their toxic effects may be potentiated.
- CNS Depressants (e.g., opioids, barbiturates, anesthetics): Additive central nervous system depression and sedation.
Frequently asked questions
What is Promethazine used for in pets?
Promethazine is used to help control nausea and vomiting, or occasionally to treat allergic reactions. * **Dry Mouth**: This medication can cause a dry mouth. You can relieve this by applying small amounts of water to your pet's tongue for 10-15 minutes. * **Sedation**: It may cause drowsiness, sedation, or mild behavior changes. Contact your veterinarian if these effects are severe or concerning. * **When to Call the Vet**: Protracted vomiting or diarrhea can be serious; contact your veterinarian if your pet's clinical signs do not improve. * **Warning Signs**: Immediately contact your veterinarian if your animal exhibits abnormal, jerky movements, tremors, or becomes rigid.
Is Promethazine safe for my pet?
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
This article is for general education and is not a substitute for professional veterinary advice. If your pet is unwell, please consult a veterinarian.
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