Summary
Highlights
Phenytoin is an anticonvulsant used for long-term seizure protection in conditions like epilepsy. It has a narrow therapeutic range of 10-20 mcg/mL. Levels below 10 indicate seizure risk, and levels above 20 indicate toxicity, requiring immediate reporting to a healthcare provider (HCP) and holding the medication. Routine blood tests are crucial to monitor therapeutic levels and liver function due to the risk of toxicity. The medication should be taken at the same time daily due to its narrow therapeutic index.
Early signs of phenytoin toxicity include ataxia (unsteady gait), hand tremors, and slurred speech. Critical adverse effects to report immediately are new and painful skin rashes, which could indicate Stevens-Johnson syndrome, and suicidal ideations. Expected side effects include bradycardia, hypotension (due to its CNS depressant effect), and gingival hyperplasia (overgrowth of gum tissue). For gingival hyperplasia, patients should practice good dental hygiene with a soft-bristle toothbrush and have regular dental visits. It's crucial not to stop the medication for gingival hyperplasia as it's an expected side effect.
Patient teaching for phenytoin includes avoiding oral contraceptives as the drug deactivates them, necessitating alternative birth control. The medication should never be stopped abruptly; it must be tapered off under medical supervision. Patients should supplement with folic acid, calcium, and vitamin D, as phenytoin decreases their absorption and bone density. When administering via tube feedings, stop feedings 1-2 hours before and after administration to ensure proper absorption. Flush the tube with 30-50 mL of tap water before and after giving the drug. For IV administration, flush with normal saline before and after. Common misconceptions to avoid are that phenytoin causes facial bleeding (only gums), metallic taste, or photosensitivity.
Levetiracetam (Keppra) is another anticonvulsant used to prevent and treat seizures, especially in high-risk patients (e.g., after brain surgery). It is often preferred over phenytoin due to minimal drug-to-drug interactions. Common side effects include drowsiness and fatigue, as it is a CNS depressant. Major adverse effects, similar to phenytoin, include suicidal thoughts and Stevens-Johnson syndrome; any new anxiety, agitation, depression, mood changes, rash, blistering, muscle/joint pain, or conjunctivitis should be reported to the HCP. Patient teaching emphasizes obtaining permission from the HCP regarding driving due to potential drowsiness and fatigue, especially during the initial 4-6 weeks of treatment.