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Increased clearance of phenytoin as the presenting feature of infectious mononucleosis
Therapeutic Drug Monitoring
|January 1, 1980
Abstract:
A 19-year-old man with posttraumatic seizures under good control with phenytoin, 500 mg/day, presented with three seizures. His blood level of phenytoin, previously in a therapeutic range, was 4.2 microgram/ml. No systemic or laboratory evidence of infectious mononucleosis was found. Ten days later, the blood picture became compatible with infectious mononucleosis, at which time his phenytoin clearance returned to normal.
Insights
A patient experienced uncontrolled seizures due to low phenytoin levels, which normalized after recovering from infectious mononucleosis. This highlights how infections can affect drug metabolism and seizure control.
Area of Science:
- Pharmacology
- Neurology
- Infectious Diseases
Background:
- Antiepileptic drug (AED) efficacy can be influenced by various physiological factors.
- Phenytoin is a commonly prescribed AED for seizure management.
- Drug-drug and drug-disease interactions require careful consideration in clinical practice.
Observation:
- A 19-year-old male with posttraumatic seizures, previously well-controlled on phenytoin, experienced breakthrough seizures.
- The patient's serum phenytoin level dropped significantly from a therapeutic range to 4.2 microgram/ml.
- Initial investigations ruled out infectious mononucleosis.
Findings:
- The patient later developed laboratory-confirmed infectious mononucleosis.
- Concurrently, phenytoin clearance normalized, and drug levels returned to the therapeutic range.
- This suggests infectious mononucleosis temporarily impaired phenytoin metabolism.
Implications:
- Infectious illnesses can precipitate subtherapeutic drug levels of certain medications.
- Clinicians should consider potential drug metabolism alterations during acute infections in patients on AEDs.
- Monitoring drug levels and adjusting dosages may be necessary during intercurrent illnesses.