Phenytek (phenytoin) Disease Interactions
There are 9 disease interactions with Phenytek (phenytoin):
Hydantoins (Includes Phenytek) ↔ Blood Dyscrasias
Severe Potential Hazard, Low plausibility
Applies to: Bone Marrow Depression/Low Blood Counts
Hematologic toxicities have been associated with the use of hydantoin anticonvulsants, particularly mephenytoin. Thrombocytopenia, leukopenia, neutropenia, agranulocytosis, pancytopenia and, rarely, hemolytic anemia, aplastic anemia and pure red cell aplasia have been reported. Therapy with hydantoin anticonvulsants should be administered cautiously in patients with preexisting blood dyscrasias and/or bone marrow depression. Complete blood counts, including platelets, should be performed prior to initiating therapy and regularly for several months thereafter. For mephenytoin, the manufacturer recommends performing counts after 2 weeks on a low dosage, after another 2 weeks when full dosage is reached, then monthly for a year, and every 3 months thereafter. Marked depression of blood counts may be indication for withdrawal of hydantoin therapy.
Hydantoins (Includes Phenytek) ↔ Liver Disease
Severe Potential Hazard, High plausibility
Applies to: Liver Disease
Hydantoin anticonvulsants are primarily metabolized by the liver. Both metabolic activity and plasma protein binding may be significantly altered in patients with liver disease, resulting in elevated drug levels (total and unbound fraction) and increased risk of toxicity. Therapy with hydantoin anticonvulsants should be administered cautiously in patients with impaired hepatic function. Reduced dosages and slower titration may be necessary. In addition, periodic monitoring of liver function is recommended, since the use of anticonvulsants, including hydantoins, has been associated with hepatotoxicity related to drug hypersensitivity. Hepatic failure and death have occurred. Hydantoin therapy should be discontinued and not readministered if evidence of liver damage is observed and felt to be drug-related.
Hydantoins (Includes Phenytek) ↔ Porphyria
Severe Potential Hazard, Moderate plausibility
Applies to: Porphyria
The use of phenytoin has rarely been associated with exacerbation of porphyria. Therapy with phenytoin should be administered cautiously in patients with porphyria. The same precaution should also be observed with other hydantoin anticonvulsants (i.e. ethotoin and mephenytoin) because of their structural and pharmacological similarities to phenytoin.
Phenytoin (Includes Phenytek) ↔ Renal Dysfunction
Severe Potential Hazard, High plausibility
Applies to: Renal Dysfunction
The plasma protein binding of phenytoin may be significantly decreased in patients with renal impairment, resulting in elevated free drug concentrations and increased risk of toxicity. This effect is proportional to the degree of renal impairment and stems from quantitative differences in serum albumin as well as qualitative differences in the ability to bind phenytoin. Therapy with phenytoin should be administered cautiously in patients with impaired renal function. Both the therapeutic and toxic plasma total phenytoin levels may be lower than normal in these patients and should be considered in dosing. Alternatively, the monitoring of unbound phenytoin concentrations may be appropriate.
Phenytoin Iv (Includes Phenytek) ↔ Cardiotoxicity
Severe Potential Hazard, High plausibility
Applies to: Heart Disease, Hypotension
The intravenous administration of phenytoin or its prodrug, fosphenytoin, is contraindicated in patients with sinus bradycardia, sino-atrial block, second and third degree AV block, and patients with Adam-Stokes syndrome. Severe cardiotoxic reactions related to depression of atrial and ventricular conduction and ventricular fibrillation have been reported with parenteral phenytoin, primarily in elderly or gravely ill patients. Hypotension and cardiovascular collapse have also been reported, usually when the drug was administered too rapidly. Therapy with intravenous phenytoin or fosphenytoin should be administered cautiously in patients with hypotension or severe myocardial insufficiency, particularly if they are elderly or seriously ill. The rate of injection should not exceed manufacturer recommendations and should be adjusted based on the patient's cardiovascular status.
Hydantoins (Includes Phenytek) ↔ Hyperglycemia
Moderate Potential Hazard, Moderate plausibility
Applies to: Diabetes Mellitus, Abnormal Glucose Tolerance
Phenytoin, particularly in high dosages, may cause hyperglycemia by inhibiting insulin release. The drug may also raise serum glucose levels in diabetic patients. Therapy with phenytoin should be administered cautiously in patients with diabetes mellitus, glucose intolerance, or a predisposition to hyperglycemia. Patients with diabetes mellitus should be monitored more closely during phenytoin therapy, and their antidiabetic regimen adjusted accordingly. The same precautions should also be observed with other hydantoin anticonvulsants (i.e. ethotoin and mephenytoin) because of their structural and pharmacological similarities to phenytoin.
Hydantoins (Includes Phenytek) ↔ Megaloblastic Anemia
Moderate Potential Hazard, Moderate plausibility
Applies to: Anemia Associated with Folate Deficiency, Folic Acid/Cyanocobalamin Deficiency
Hydantoin anticonvulsants may interfere with folate metabolism and precipitate macrocytosis and megaloblastic anemia, which usually respond to folic acid therapy. These reactions have been fairly uncommon but may be of concern in patients with megaloblastic anemia or folate deficiency receiving hydantoin therapy.
Hydantoins (Includes Phenytek) ↔ Osteomalacia
Moderate Potential Hazard, Moderate plausibility
Applies to: Vitamin D Deficiency
Phenytoin may interfere with vitamin D metabolism. Hypocalcemia and osteomalacia have been reported. Therapy with phenytoin should be administered cautiously in patients with preexisting vitamin D deficiency. The same precaution should also be observed with other hydantoin anticonvulsants (i.e. ethotoin and mephenytoin) because of their structural and pharmacological similarities to phenytoin.
Phenytoin (Includes Phenytek) ↔ Thyroid Function Tests
Moderate Potential Hazard, Moderate plausibility
Applies to: Thyroid Disease
Phenytoin may decrease serum PBI (protein-bound iodine) levels without associated thyroid disturbance. Free thyroxine concentrations may also be decreased, while resin or red cell T3 uptake values may be increased. Clinicians should be cognizant of these effects when prescribing or administering phenytoin therapy to patients with thyroid disorders.
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Phenytek (phenytoin) drug Interactions
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Phenytek (phenytoin) alcohol/food Interactions
There are 2 alcohol/food interactions with Phenytek (phenytoin)
See also...
Drug Interaction Classification
The classifications below are a general guideline only. It is difficult to determine the relevance of a particular drug interaction to any individual given the large number of variables.
| Major | Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit. |
| Moderate | Moderately clinically significant. Usually avoid combinations; use it only under special circumstances. |
| Minor | Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan. |
Do not stop taking any medications without consulting your healthcare provider.
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