Aurantin Drug Interactions

Drug Interactions: No drugs are known to interfere with the conversion of fosphenytoin to phenytoin. Conversion could be affected by alterations in the level of phosphatase activity, but given the abundance and wide distribution of phosphatases in the body, it is unlikely that drugs would affect this activity enough to affect conversion of fosphenytoin to phenytoin.
Drugs highly bound to albumin could increase the unbound fraction of fosphenytoin sodium (Aurantin). Although it is unknown whether this could result in clinically significant effects, caution is advised when administering fosphenytoin sodium (Aurantin) with other drugs that significantly bind to serum albumin.
The pharmacokinetics and protein binding of fosphenytoin, phenytoin, and diazepam were not altered when diazepam and fosphenytoin were concurrently administered in single submaximal doses.
The most significant drug interactions following administration of fosphenytoin sodium (Aurantin) are expected to occur with drugs that interact with phenytoin.
Phenytoin is extensively bound to plasma proteins and is prone to competitive displacement. Phenytoin is metabolized by hepatic cytochrome P450 (CYP) enzymes CYP2C9 and CYP2C19, and is particularly susceptible to inhibitory drug interactions because it is subject to saturable metabolism. Inhibition of metabolism may produce significant increases in circulating phenytoin concentrations and enhance the risk of drug toxicity.
Phenytoin is a potent inducer of hepatic drug-metabolizing enzymes and may reduce the levels of drugs metabolized by these enzymes.
There are many drugs that may increase or decrease serum phenytoin levels or that phenytoin may affect. Serum level determinations for phenytoin are especially helpful when possible drug interactions are suspected.
The most commonly occurring drug interactions are listed as follows.
Drugs That May Increase Phenytoin Serum Levels: Table 6 summarizes the drug classes that may potentially increase phenytoin serum levels. (See Table 6.)

Click on icon to see table/diagram/image

Drugs That May Decrease Phenytoin Plasma Levels: Table 7 summarizes the drug classes that may potentially decrease phenytoin plasma levels. (See Table 7.)

Click on icon to see table/diagram/image

Drugs That May Increase or Decrease Phenytoin Serum Levels: Table 8 summarizes the drug classes that may either increase or decrease phenytoin serum levels. (See Table 8.)

Click on icon to see table/diagram/image

Drugs Whose Serum Levels and/or Effects May be Altered by Phenytoin: Table 9 summarizes the drug classes whose serum levels and/or effects may be altered by phenytoin. (See Table 9.)

Click on icon to see table/diagram/image

Although not a true drug interaction, tricyclic antidepressants may precipitate seizures in susceptible patients and phenytoin dosage may need to be adjusted.
Drug-Laboratory Test Interactions: Phenytoin may cause decreased serum levels of protein-bound iodine (PBI). It also may 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). Phenytoin may affect blood calcium and blood sugar metabolism tests.
Monitoring of plasma phenytoin concentrations may be helpful when possible drug interactions are suspected.