Phenytoin blood testing is ordered because phenytoin blood levels must be maintained within a narrow therapeutic range. If levels are too low, the affected person may experience seizures; if they are too high, the person may experience symptoms associated with phenytoin toxicity.
.
Likewise, people ask, why would phenytoin levels be low?
Patients with unusually low levels may be noncompliant or hypermetabolizers of phenytoin. Unusually high levels result from liver disease, congenital enzyme deficiency or drug interactions which result in metabolic interference.
what are the indications of an abnormal Phenytoin serum level? Total phenytoin levels (mcg/mL) and typical corresponding signs and symptoms are as follows:
- Lower than 10 - Rare.
- Between 10 and 20 - Occasional mild nystagmus.
- Between 20 and 30 - Nystagmus.
- Between 30 and 40 - Ataxia, slurred speech, nausea, and vomiting.
- Between 40 and 50 - Lethargy and confusion.
People also ask, what can cause low Dilantin levels?
Drugs which may decrease phenytoin levels include: carbamazepine, chronic alcohol abuse, reserpine, and sucralfate. Moban® brand of molindone hydrochloride contains calcium ions which interfere with the absorption of phenytoin.
What is the normal phenytoin level?
Although the reference range is between 10 and 20 µg/mL, about half of patients' seizures are controlled at values lower and higher than the therapeutic range. Some adverse effects of phenytoin are related to specific serum levels. Nystagmus is frequently observed at levels greater than 20 µg/mL.
Related Question AnswersWhat happens if phenytoin is low?
Phenytoin blood testing is ordered because phenytoin blood levels must be maintained within a narrow therapeutic range. If levels are too low, the affected person may experience seizures; if they are too high, the person may experience symptoms associated with phenytoin toxicity.How do I raise my phenytoin level?
If the phenytoin concentration is < 7 mcg/mL, the dose may be increased by 100 mg/day. If the phenytoin concentration is 7-12 mcg/mL, the dose may be increased by 50 mg/day. If the phenytoin concentration is >12 mcg/mL, the dose may be increased by 30 mg/day.How often should phenytoin levels be checked?
A level can be taken 2-4 hours following an IV loading or top-up dose (12-24 hours for oral doses) and levels should then be monitored every 24 hours until control is achieved and concentration has stabilised.How do you check phenytoin levels?
After a patient has received a loading dose of intravenous phenytoin, levels can be checked one hour after the dose. If loading is achieved by oral dosing, phenytoin levels can be checked 24 hours after the last dose10. This level can aid in determining maintenance dose or need to reload.What can affect phenytoin levels?
Drugs which may increase phenytoin serum levels include: acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, cimetidine, diazepam, dicumarol, disulfiram, estrogens, ethosuximide, fluoxetine, H2-antagonists, halothane, isoniazid, methylphenidate, phenothiazines, phenylbutazone, salicylates, succinimidesDoes phenytoin cause weight gain?
Weight gain or loss is not an integral part of epilepsy although a sedentary lifestyle can contribute to weight gain. AEDs associated with weight gain are gabapentin, pregabalin, valproic acid, and vigabatrin and possibly, carbamazepine. Weight neutral AEDs are lamotrigine, levetiracetam, and phenytoin.What are the long term side effects of phenytoin?
Side effects of phenytoin include sedation, a cerebellar syndrome, phenytoin encephalopathy, psychosis, locomotor dysfunction, hyperkinesia, megaloblastic anemia, decreased serum folate level, decreased bone mineral content, liver disease, IgA deficiency, gingival hyperplasia, and a lupus-like hypersensitivity syndromeWhat drugs decrease effectiveness of phenytoin?
Drugs that may decrease phenytoin levels and reduce effectiveness include carbamazepine, chronic alcohol abuse, reserpine, and sucralfate (Carafate).Does Dilantin show up as a barbiturate?
Phenytoin sodium is an antiepileptic drug. Phenytoin sodium is related to the barbiturates in chemical structure, but has a five-membered ring. Each Dilantin— 100 mg Extended Oral Capsule—contains 100 mg phenytoin sodium.How does phenytoin cause folate deficiency?
Folate is present in food in a polyglutamate form, which is then converted into monoglutamates by intestinal conjugase to be absorbed by the jejunum. Phenytoin acts by inhibiting this enzyme, thereby causing folate deficiency, and thus megaloblastic anemia.What is a seizure?
A seizure is a sudden, uncontrolled electrical disturbance in the brain. It can cause changes in your behavior, movements or feelings, and in levels of consciousness. Most seizures last from 30 seconds to two minutes. A seizure that lasts longer than five minutes is a medical emergency.What drugs interact with phenytoin?
Drugs That Affect Phenytoin Concentrations| Interacting Agent | Examples |
|---|---|
| Drugs that may increase phenytoin serum levels | |
| Antiepileptic drugs | Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate |
| Azoles | Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole |
| Antineoplastic agents | Capecitabine, fluorouracil |
