Psychiatric Drugs and Medications Q 28
When administering IV phenytoin (Dilantin), the nurse should:
A. Administer it at a rate 100 mg/min.
B. Protect the drug from light exposure.
C. Mix the drug in dextrose solution.
D. Mix the drug in saline solution.
Correct Answer: D. Mix the drug in saline solution.
Phenytoin must be mixed in saline solution only. It requires dilution with sodium chloride. Phenytoin is a hydantoin derivative, a first-generation anticonvulsant drug that is effective in the treatment of generalized tonic-clonic seizures, complex partial seizures, and status epilepticus without significantly impairing neurological function.
Option A: Phenytoin should be administered at a rate of 50 mg/min. The drug is slowly administered intravenously directly into a large central or peripheral vein through an IV catheter less than 20 gauge, not exceeding a rate of 50 mg/minute.
Option B: There is no need to protect phenytoin from light because it does not destabilize with light exposure. Knowledge of its pharmacokinetic properties is crucial for correct interpretation of total serum concentrations when protein binding becomes altered due to hypoalbuminemia, renal failure, or interaction with other protein-bound drugs such as valproate.
Option C: Phenytoin will precipitate when mixed with a dextrose solution. Crystals will form when diluted with dextrose solution. In therapeutic doses, phenytoin is absorbed entirely and reaches peak plasma concentration at 1.5 to 3 hours. However, in settings of acute ingestions, absorption tends to last longer than two weeks; this is potentially attributable to its effects on reducing gastrointestinal motility and poor water solubility.