Chemical Name : Phenytoin
Dilantin Information : PHENYTOIN is an anticonvulsant drug which can be useful in the treatment of epilepsy. The primary site of action appears to be the motor cortex where spread of seizure activity is inhibited. Possibly by promoting sodium efflux from neurons, PHENYTOIN tends to stabilize the threshold against hyperexcitability caused by excessive stimulation or environmental changes capable of reducing membrane sodium gradient. This includes the reduction of posttetanic potentiation at synapses. Loss of posttetanic potentiation prevents cortical seizure foci from detonating adjacent cortical areas. PHENYTOIN reduces the maximal activity of brain stem centers responsible for the tonic phase of tonic-clonic (grand mal) seizures.
Dilantin Side Effects : CNS:
The most common PHENYTOIN side effects include nystagmus, ataxia, slurred speech, decreased coordination and mental confusion.Other PHENYTOIN side effects like Dizziness, insomnia, transient nervousness, motor twitchings, and headaches have also been observed. There have also been rare reports of PHENYTOIN side effects like phenytoin induced dyskinesias, including chorea, dystonia, tremor and asterixis, similar to those induced by phenothiazine and other neuroleptic drugs.
PHENYTOIN side effects like predominantly sensory peripheral polyneuropathy have been observed in patients receiving long-term dosage of this medicine
PHENYTOIN side effects like:Nausea, vomiting, and constipation.
PHENYTOIN side effects like Dermatological manifestations sometimes accompanied by fever have included scarlatiniform or morbilliform rashes. A morbilliform rash (measles-like) is the most common; other types of dermatitis are seen more rarely. Other more serious forms of PHENYTOIN side effects which may be fatal have included bullous, exfoliative or purpuric dermatitis, lupus erythematosus, Stevens-Johnson syndrome and toxic epidermal necrolysis (see Precautions).
PHENYTOIN side effects like Hemopoietic complications, some fatal, have occasionally been reported in association with administration of phenytoin. These have included thrombocytopenia, leukopenia, granulocytopenia, agranulocytosis, and pancytopenia with or without bone marrow suppression. While macrocytosis and megaloblastic anemia have occurred, these conditions usually respond to folic acid therapy. Lymphadenopathy including benign lymph node hyperplasia, pseudolymphoma, lymphoma, and Hodgkins's Disease have been reported (see Warnings).
PHENYTOIN side effects like Coarsening of the facial features, enlargement of the lips, gingival hyperplasia, hypertrichosis and Peyronie's Disease.
PHENYTOIN side effects like Systemic lupus erythematosus, periarteritis nodosa, toxic hepatitis, liver damage, and immunoglobulin abnormalities may occur.
The liver is the chief site of biotransformation of PHENYTOIN ; patients with impaired liver function, elderly patients, or those who are gravely ill may show early signs of toxicity.
A small percentage of individuals who have been treated with phenytoin have been shown to metabolize the drug slowly. Slow metabolism may be due to limited enzyme availability and lack of induction; it appears to be genetically determined.
PHENYTOIN should be discontinued if a skin rash appears (see Warnings regarding drug discontinuation). If the rash is exfoliative, purpuric, or bullous or if lupus erythematosus, Stevens-Johnson syndrome or toxic epidermal necrolysis is suspected, use of this drug should not be resumed and alternative therapy should be considered (see Adverse Effects). If the rash is of a milder type (measles-like or scarlatiniform), therapy may be resumed after the rash has completely disappeared. If the rash recurs upon reinstitution of therapy, further phenytoin medication is contraindicated.
Hyperglycemia, resulting from the drug's inhibitory effects on insulin release, has been reported. Phenytoin may also raise the serum glucose level in diabetic patients.
Osteomalacia has been associated with PHENYTOIN therapy and is considered to be due to phenytoin's interference with vitamin D metabolism.
PHENYTOIN is not indicated for seizures due to hypoglycemic or other metabolic causes. Appropriate diagnostic procedures should be performed as indicated.
PHENYTOIN is not effective for absence (petit mal) seizures. If tonic-clonic (grand mal) and absence (petit mal) seizures are present, combined drug therapy is needed.
Serum levels of PHENYTOIN sustained above the optimal range may produce confusional states referred to as delirium, psychosis, or encephalopathy, or rarely, irreversible cerebellar dysfunction. Accordingly, at the first sign of acute toxicity, plasma level determinations are recommended. Dose reduction of PHENYTOIN therapy is indicated if plasma levels are excessive; if symptoms persist, termination is recommended (see Warnings).
Information for the Patient:
Patients taking phenytoin should be advised of the importance of adhering strictly to the prescribed dosage regimen, and of informing the physician of any clinical condition in which it is not possible to take the drug orally as prescribed, e.g. surgery, etc.
Patients should also be cautioned on the use of other drugs or alcoholic beverages without first seeking the physician's advice.
Patients should be instructed to call their physician if skin rash develops.
The importance of good dental hygiene should be stressed in order to minimize the development of gingival hyperplasia and its complications.
Do not use capsules which are discolored.
PHENYTOIN serum level determinations may be necessary to achieve optimal dosage adjustments.
There are many drugs which may increase or decrease PHENYTOIN levels or which PHENYTOIN may affect. The most commonly occurring drug interactions are listed below.
Drugs which may increase PHENYTOIN serum levels include: chloramphenicol, dicumarol, disulfiram, tolbutamide, isoniazid, phenylbutazone, acute alcohol intake, salicylates, chlordiazepoxide, phenothiazines, diazepam, estrogens, ethosuximide, halothane, methylphenidate, sulfonamides, cimetidine, trazodone.
Drugs which may decrease PHENYTOIN levels include: carbamazepine, chronic alcohol abuse, reserpine. Moban brand of molindone HCl contains calcium ions which interfere with the absorption of phenytoin. Ingestion times of phenytoin and antacid preparations containing calcium should be staggered in patients with low serum phenytoin levels to prevent absorption problems.
Drugs which may either increase or decrease PHENYTOIN serum levels include: phenobarbital, valproic acid, and sodium valproate. Similarly, the effect of phenytoin on phenobarbital, valproic acid and sodium valproate serum levels is unpredictable.
Although not a true drug interaction, tricyclic antidepressants may precipitate seizures in susceptible patients and phenytoin dosage may need to be adjusted.
Drugs whose efficacy is impaired by phenytoin include: corticosteroids, coumarin anticoagulants, oral contraceptives, quinidine, vitamin D, digitoxin, rifampin, doxycycline, estrogens, furosemide.
Serum level determinations are especially helpful when possible drug interactions are suspected.
Drug/Laboratory Test Interactions:
PHENYTOIN may cause decreased serum levels of protein-bound iodine (PBI). It may also produce lower than normal values for dexamethasone or metyrapone tests. PHENYTOIN may cause increased serum levels of glucose, alkaline phosphatase, and gamma glutamyl transpeptidase (GGT).
Infant breast-feeding is not recommended for women taking this drug because PHENYTOIN appears to be secreted in low concentrations in human milk.
The generic alternative is not manufatured by the company that makes the brand product.
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