Phenytoin sodium prompt

[FEN-ih-toyn] Pregnancy Category: C

Diphenylan Sodium [Rx] Classification: Anticonvulsant, hydantoin type; antiarrhythmic (type I)_

See also Anticonvulsants. Action/Kinetics: Acts in the motor cortex of the brain to reduce the spread of electrical discharges from the rapidly firing epileptic foci in this area. Phenytoin extended is designed for once-a-day dosage. It has a slow dissolution rateā€”no more than 35% in 30 min, 30%-70% in 60 min, and less than 85% in 120 min. Absorption is variable following PO dosage. Peak serum levels: PO, 4-8 hr. Since the rate and extent of absorption depend on the particular preparation, the same product should be used for a particular client. Peak serum levels (following IM): 24 hr (wide variation). Therapeutic serum levels: 5-20 mcg/mL. tvi: 8-60 hr (average: 20-30 hr). Steady state: 7-10 days after initiation. Bio-transformed in the liver. Both inactive metabolites and unchanged drug are excreted in the urine.

As an antiarrhythmic, phenytoin increases the electrical stimulation threshold of heart muscle, although it is less effective than quinidine, procai-namide, or lidocaine. Onset: 30-60 min. Duration: 24 hr or more. tVi: 22-36 hr. Therapeutic serum level: 10-20 mcg/mL.

Uses: Chronic epilepsy, especially of the tonic-clonic, psychomotor type. Not effective against absence seizures and may even increase the frequency of seizures in this disorder. Parenteral phenytoin is sometimes used to treat status epilepticus and to control seizures during neuro-surgery.

PO for certain PVCs and IV for PVCs and tachycardia. Particularly useful for arrhythmias produced by digitalis overdosage.

Non-FDA Approved Uses: Paroxysmal choreoathetosis; to treat blistering and erosions in clients with recessive dystrophic epidermolysis bullosa; episodic dyscontrol; trigeminal neuralgia; as a muscle relaxant in neuromyo-tonia, myotonia congenita, or myoton-ic muscular dystrophy; to treat cardiac symptoms in overdosage of tricyclic antidepressants. Severe preeclamp-sia.

Contraindications: Hypersensitiv-ity to hydantoins, exfoliative dermatitis, sinus bradycardia, second- and third-degree AV block, clients with Adams-Stokes syndrome, SA block. Lactation.

Special Concerns: Use with caution in acute, intermittent porphyria. Administer with extreme caution to clients with a history of asthma or other allergies, impaired renal or hepatic function, and heart disease (hypotension, severe myocardial insufficiency). Abrupt withdrawal may cause status epilepticus. Combined drug therapy is required if petit mal seizures are also present. Side Effects: CNS: Most commonly, drowsiness, ataxia, dysarthria, confusion, insomnia, nervousness, irritability, depression, tremor, numbness, headache, psychoses, increased seizures. Choreoathetosis following IV use. Oral: Gingival hyperplasia, oral ulceration, loss of taste. GI: N&V, either diarrhea or constipation. Dermatologic: Various dermatoses including a measles-like rash (common), scarlatiniform, maculopapu-lar, and urticarial rashes. Rarely, drug-induced lupus erythematosus, Stevens-Johnson syndrome, exfoliative or purpuric dermatitis, and toxic epidermal necrolysis. Alopecia, hirsut-ism. Skin reactions may necessitate withdrawal of therapy. Hematopoiet-ic: Leukopenia, granulocytopenia, thrombocytopenia, pancytopenia, agranulocytosis, macrocytosis, megalo-blastic anemia, leukocytosis, monocy-tosis, eosinophilia, simple anemia, aplastic anemia, hemolytic anemia. Hepatic: Liver damage, toxic hepatitis, hypersensitivity reactions involving the liver including hepato-cellular degeneration and fatal hepatocellular necrosis. Ophthalmic: Diplopia, nystagmus, conjunctivitis. Miscellaneous: Hyperglycemia, chest pain, edema, fever, photophobia, weight gain, pulmonary fibrosis, lymph node hyperplasia, gyneco-mastia, periarteritis nodosa, depression of IgA, soft tissue injury at injection site, coarsening of facial features, Peyronie's disease, enlarged lips.

Rapid parenteral administration may cause serious CV effects, including hypotension, arrhythmias, CV collapse, and heart block, as well as CNS depression.

Many clients have a partial deficiency in the ability of the liver to degrade phenytoin, and as a result, toxicity may develop after a small PO dose. Liver and kidney function tests and hematopoietic studies are indicated prior to and periodically during drug therapy.

Drug Interactions Acetaminophen / i Effect of acetaminophen due to T breakdown by liver; however, hepatotoxicity may be T

Alcohol, ethyl / In alcoholics, i effect of phenytoin due to T breakdown by liver

Antacids / i Effect of phenytoin due to i GI absorption Antidepressants, tricyclic / May T incidence of epileptic seizures or T effect of phenytoin by i plasma protein binding

Barbiturates / Effect of phenytoin may be T , i , or not changed; possible T effect of barbiturates Benzodiazepines / T Effect of phen-ytoin due to i breakdown by liver

Carbamazepins / i Effect of phenytoin or carbamazepine due to T breakdown by liver Cimetidine / T Effect of phenytoin due to i breakdown by liver Clonazepam / i Plasma levels of clonazepam or phenytoin; or, T risk of phenytoin toxicity Corticosteroids / Effect of corticos-teroids i due to T breakdown by liver; also, corticosteroids may mask hypersensitivity reactions due to phenytoin

Doxycycline / i Effect of doxycy-cline due to T breakdown by liver Fluconazole / T Effect of phenytoin due to i breakdown by liver Ibuprofen / T Effect of phenytoin Meperidine / i Effect of meperidine due to T breakdown by liver; toxic effects of meperidine may T due to accumulation of active metabolite (normeperidine)

Metronidazole / T Effect of pheny-toin due to i breakdown by liver Miconazole / T Effect of phenytoin due to i breakdown by liver Phenothiazines / T Effect of pheny-toin due to i breakdown by liver Phenylbutazone / T Effect of phenytoin due to i breakdown by liver and i plasma protein binding Salicylates / T Effect of phenytoin by i plasma protein binding Sucralfate / i Effect of phenytoin due to i absorption from GI tract Sulfonamides / T Effect of pheny-toin due to i breakdown in liver Trimethoprim / T Effect of pheny-toin due to i breakdown by liver How Supplied: Phenytoin: Chew tablet: 50 mg; Suspension: 100 mg/4 mL, 125 mg/5 mL. Phenytoin sodium, extended: Capsule, extended release: 30 mg, 100 mg. Phenytoin sodium, parenteral: Injection: 50 mg/mL. Phenytoin sodium prompt: Capsule: 100 mg

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