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Phenytoin
Brand Name: Dilantin
Overview
Dilantin, the brand name for phenytoin, is an anticonvulsant that acts on the
motor cortex to inhibit seizure activity. It seems to work by making neurons less
hyper-excitable: neurons cannot begin electrical signals or transmit signals to
other neurons as easily.
It takes at least 7-10 days, and may take up to three weeks or more to achieve
therapeutic levels and determine if Dilantin is helping to control seizures.
Sometimes Dilantin is combined with the drug Phenobarbital to control seizures
in patients who require both drugs. It is not recommended that patients be given the
combination Dilantin with Phenobarbital until these drugs have both been tried
separately.
Dilantin is also available as Dilantin suspensions and Dilantin Infatabs.
Why
is this drug prescribed?
Dilantin is used to treat:
- Tonic-clonic (grand mal) seizures
- Complex-partial (psychomotor, temporal lobe) seizures
- Seizures occurring during or after brain surgery
Note: Dilantin has not been found effective against absence (petit mal) seizures.
Other drugs must be used to treat this type of seizure.
Warnings
and Precautions
Phenobarbital (found in Dilantin with Phenobarbital) may be habit forming.
Abruptly discontinuing Dilantin may cause an increased number and/or severity of
seizures. Dosage should be gradually tapered when it is discontinued, except in the
case of an allergy or other serious adverse reaction to the medication.
Dilantin has been associated with lymphadenopathy (swollen lymph nodes), though
it has not been proven to cause it. Symptoms that may indicate lymph nodes are
affected include fever, rash, and liver problems. If a patient on Dilantin develops
lymph node problems, another drug should be used.
For Pregnant or Nursing Mothers: Some reports show an association between use of
Dilantin during pregnancy and an increased incidence of birth defects, however
Dilantin is not proven to be a direct cause, and nearly all babies born to mothers
on anti-epileptic medication are normal. Also, the relative risks of using
anti-epileptics and the danger of seizures to the fetus should be considered.
Drug serum levels should be monitored closely in pregnancy, when there is
frequently an increase in seizures.
Contraindications
Dilantin should Not be used for people with the following medical conditions:
- Allergy or hypersensitivity to phenytoin or other hydantoins
- Porphyria (abnormal pigment metabolism), including latent porphyria
- Patients who develop a serious rash while taking Dilantin
Precautions
Dilantin may be used with caution in people with the following conditions:
- Kidney disease
- Liver disease
- Acidosis (acidic blood)
- Obesity
- Diabetes or hyperglycemia – Dilantin may inhibit insulin release and may increase glucose levels in diabetics.
- Seizures due to hypoglycemia or other metabolic problems
Adverse
Reactions
Dilantin may cause the following reactions:
- Ataxia (unsteady or shaky movements)
- Drowsiness or sleepiness
- Confusion
- Nystagmus (rapid and involuntary eye movements)
- Headache
- Nervousness
- Insomnia
- Reduced blood calcium levels
- High blood sugar (hyperglycemia)
- Seizures
- Decreased libido
- Rash (if severe, indicating that Dilantin should not be used)
- Osteomalacia (softening of bones from insufficient vitamin D metabolism)
Interactions
with Drugs and Other Substances
Drugs or substances that may interact with Dilantin include:
- Birth control pills: Dilantin may decrease the effectiveness of oral contraceptives.
- Tylenol (acetaminophen), Wellbutrin (bupropion), Atromid-S (clofibrate), Premarin (conjugated estrogens), cortisone steriods, Sandimmune (cyclosporine), Norpace (disopyramide), Vibramycin (doxycycline), Sporanox (itraconazole), Sinemet (levodopa), Synthroid (levothyroxine), Demerol (meperidine), methadone, Mexitil (mexiletine), Micatin (miconazole), oral antidiabetic drugs, Paxil (paroxetine), Quinaglute (quinidine), and Norvir (ritonavir): Dilantin may reduce the effectiveness of these medications
- Codarone (amiodarone), Chloromycetin (chloramphenicol), Tagamet (cimetidine), Bactrim (cotrimoxazole), Cardizem (diltiazem), Antabuse (disulfiram), Felbatol (felbamate), Diflucan (fluconazole), Prozac (fluoxetine), Luvox (fluvoxamine), Neurontin (gabapentin), ibuprofen, INH (isoniazid), Adalat (nifedipine), Prilosec (omeprazole), Phenurone (phenacemide), sulfonamides, tricyclic antidepressants (TCAs), Trimpex (trimethoprim), Depakene (valproic acid), Effexor (venlafaxine), Tegretol (carbamezapine): These medications may increase Dilantin’s effects.
- Blenoxane (bleomycin), BiCNU (carmustine), Platinol (cisplatin), Hyperstat (diazoxide), folic acid, Mexate (methotrexate), Rifadin (rifampin), and Velban (vinblastine): These medications may decrease Dilantin’s effects.
- Alcohol – large amounts of alcohol may increase the levels of Dilantin in the short term, while long-term/chronic alcohol abuse may decrease Dilantin’s effects.
Sources
http://www2.health-center.com/db/PageReq?SessionID=109352388.1033442345315&TopicID=344&PageID=1578&Action=view
http://www.mentalhealth.com
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