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Industry: Email Alert RSS FeedDilantin® Jeopardy: Avoiding The Dangers of Phenytoin
MedSurg Nursing, Dec, 1998 by Michael L. Schlicher
Phenytoin sodium (Dilantin[R]), is a widely known anticonvulsant medication that can cause serious side effects and interactions with numerous other medications. Nurses should thoroughly familiarize themselves with this medication's properties in order to practice safely.
Phenytoin sodium (Dilantin[R]), is a widely known anticonvulsant medication that is commonly used in many emergency departments (EDs) and hospitals throughout the United States for treating status epilepticus and other psychomotor seizures resulting from head injury. In fact, 1 out of 10 people who experience seizures in their life will be prescribed phenytoin (Shantz & Spitz, 1993). Despite its popularity, phenytoin can be problematic due to its numerous catastrophic drug complications and its dangerous and even fatal side effects. Many health care providers are simply not familiar with phenytoin prior to administering it. This lack of familiarity may contribute to a lack of knowledge regarding proper administration techniques as well as inadequate patient education prior to discharge. Having a proper knowledge of phenytoin, including its effects, pharmacokinetics, potential drug interactions, and administration techniques are paramount for any nurse who will administer it.
Setting the Scene
John B., a 27-year-old male, arrives to a busy ED having an active seizure. His wife states he has a history of seizures and takes 200 mg of P.O. phenytoin to help control his disorder. He is also a diabetic which is currently controlled by using 5 mg of P.O. Micronase[R] daily. The EMT who responded to John's call for help started an IV of D5W and drew a D-stick which indicated John's blood glucose was 125. The physician instructs the nurse to draw a CBC and a lab panel to include a serum phenytoin level. He orders 2 mg of Ativan[R] to be given IV. Shortly after giving the Ativan IV, John's seizures dissipate and he goes into a post-ictal state. John's vital signs are currently stable with a BP of 128/76, a heart rate of 80, respirations at 18, and a rectal temperature of 99.9 F.
Upon review of the lab results, the nurse notifies the doctor of John's phenytoin level which is 3 mcg/ml, greatly below the desired plasma concentration of 10 to 20 mcg/ml (BeDell et al., 1996). The doctor orders 250 mg of phenytoin IV "now," followed by an IV drip of 1 gram phenytoin to be infused over the next 2 hours. The nurse has never instituted a phenytoin drip before, but proceeds. The 250 mg of phenytoin is given IV push over 1 minute in the patient's IV, with the D5W running wide open. The nurse then leaves to go prepare the drip as ordered. As the nurse prepares the drip by mixing 1 gram of phenytoin in a 500 cc bag of normal saline, she suddenly notices that John's blood pressure has dropped to 60/40, his heart rate has increased to 155 beats per minute, and his respirations have decreased to 6 breaths per minute. A few seconds later, John goes into ventricular fibrillation and then cardiac arrest.
Sadly, what appeared to be a routine seizure disorder treatment evolved into a serious disaster. John's demise was a direct result of the nurse making a critical error in administrating phenytoin and from not knowing the possible complications associated with this drug. Giving phenytoin improperly can place the patient and the nurse in grave jeopardy. To prevent this scenario in their institutions, adult health nurses must be aware of some of the special considerations associated with administrating phenytoin.
Pharmacokinetics
Phenytoin falls under the classification of hydantoins, one of the four major classes of anticonvulsants. It has been useful in treating status epilepticus for both generalized tonic-clonic seizure (formerly called a grand mal seizure), and partial seizures (Keltner, Schwecke, & Bostrom, 1991). Phenytoin also has a secondary classification as an anti-arrhythmic, and can be used for arrhythmias associated with cardiac glycoside toxicity by improving AV conduction (Phillips & Kuhn, 1996). Related to the barbiturates in chemical structure, phenytoin appears to work on the motor cortex to inhibit spreading of seizure activity (Shannon, Wilson, & Stang, 1995). Its plasma half-life in humans after intravenous administration ranges from 10 to 22 hours (BeDell et al., 1996). The half-life influences how often the patient needs the drug and how soon the drug reaches what is called a "steady state." This is when the level of phenytoin in the body equals the amount being removed by the body.
Phenytoin is mostly metabolized through oxidation in the liver to an inactive metabolite known as 5p-hydroxyphenyl-5phenylhydantoin or HPPH (Olin, Hebel, & Cada, 1996). Because the enzyme that converts phenytoin to HPPH is quickly saturated, plasma levels of phenytoin can double or triple resulting in toxicity. Therefore, nurses must keep a careful eye on their patients' phenytoin levels during the immediate crisis and later during drug adjustments. The therapeutic serum level is usually between 10 to 20 mcg/ml. Toxic levels are considered to be anything greater than 20 mcg/ml (Vallerand & Deglin, 1994). Due to phenytoin's rather long plasma half-life, it may take a patient 7 to 10 days to reach his therapeutic serum level (steady state) when starting on this drug.
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