Phenytoin Sodium
Also known as: Dilantin, Phenytek
- **Strict Schedule**: Give this medication exactly as prescribed. Missing doses can lead to breakthrough seizures or dangerous heart rhythms. - **Administration**: Giving the medication with food may enhance absorption and decrease stomach upset. - **Watch for Side Effects**: Notify your veterinarian immediately if your pet becomes extremely lethargic, loses their appetite, vomits, or appears wobbly/drunk (ataxic). - **Dental Health**: In dogs, this drug can cause overgrowth of the gums (gingival hyperplasia). Regular dental check-ups and good oral hygiene are important. - > **Safety Warning**: Never share human medications with your pet. The way animals process this drug is vastly different from humans, and incorrect dosing can be fatal.
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
- Treatment of ventricular arrhythmias
- Treatment of seizures
- Seizures
- Digoxin induced arrhythmias
- Treatment of ventricular dysrhythmias
- Treatment of seizures
- Treatment of seizures
- Treatment of seizures
- Treatment of ventricular arrhythmias
- Treatment of ventricular arrhythmias
- Treatment (or prophylaxis) of digitalis intoxication
- Treatment of hypoglycemia secondary to tumor
How it is given
Possible side effects
- Dogs: Anorexia, vomiting, ataxia, sedation, gingival hyperplasia, hepatotoxicity (elevated ALT, decreased albumin, hepatic lipidosis)
- Cats: Ataxia, sedation, anorexia, dermal atrophy syndrome, thrombocytopenia
- Horses: Excitement, recumbency (at high plasma concentrations)
Cautions & contraindications
- Hypersensitivity to phenytoin or other hydantoins
- Intravenous use is contraindicated in 2nd or 3rd degree heart block
- Sinoatrial block
- Adams-Stokes syndrome
- Sinus bradycardia
- > **Hepatotoxicity Warning**: Chronic therapy in dogs requires regular monitoring of liver function due to the risk of hepatocellular hypertrophy, necrosis, and hepatic lipidosis. - **Pregnancy**: Potentially teratogenic (FDA Category D / Papich Class C). It readily crosses the placenta and is excreted in maternal milk. Use only when benefits clearly outweigh risks. - **Feline Sensitivity**: Cats metabolize phenytoin extremely slowly. Use is highly controversial and requires diligent monitoring to prevent severe toxicity. - **IV Administration**: Must be given slowly. Rapid IV injection can cause severe hypotension and cardiac arrhythmias.
Drug interactions
- Chloramphenicol: Significantly increases the serum half-life of phenytoin (e.g., from 3 to 15 hours in dogs) by inhibiting its hepatic metabolism.
- Lithium: The toxicity of lithium may be enhanced.
- Meperidine: Phenytoin may decrease the analgesic properties of meperidine but enhance its toxic effects.
- Phenobarbital / Primidone: Altered pharmacologic effects; potential for additive hepatotoxicity. Weigh risks vs. benefits before combining.
- Allopurinol, Cimetidine, Diazepam, Isoniazid, Salicylates, Sulfonamides, Trimethoprim, Valproic Acid: May increase the pharmacologic effects and toxicity of phenytoin.
- Antacids, Barbiturates, Calcium, Folic Acid, Theophylline: May decrease the pharmacologic activity of phenytoin.
- Corticosteroids, Doxycycline, Estrogens, Furosemide, Quinidine: Phenytoin may decrease the pharmacologic activity of these agents via hepatic enzyme induction.
Frequently asked questions
What is Phenytoin Sodium used for in pets?
- **Strict Schedule**: Give this medication exactly as prescribed. Missing doses can lead to breakthrough seizures or dangerous heart rhythms. - **Administration**: Giving the medication with food may enhance absorption and decrease stomach upset. - **Watch for Side Effects**: Notify your veterinarian immediately if your pet becomes extremely lethargic, loses their appetite, vomits, or appears wobbly/drunk (ataxic). - **Dental Health**: In dogs, this drug can cause overgrowth of the gums (gingival hyperplasia). Regular dental check-ups and good oral hygiene are important. - > **Safety Warning**: Never share human medications with your pet. The way animals process this drug is vastly different from humans, and incorrect dosing can be fatal.
Is Phenytoin Sodium 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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