Side Effects of Corzyna (Cycloserine)
Cycloserine (Corzyna) commonly causes neuropsychiatric side effects including anxiety, depression, and psychosis, which should be closely monitored monthly or more frequently if symptoms develop. 1
Neuropsychiatric Side Effects
Cycloserine crosses the blood-brain barrier effectively, with CSF concentrations approaching those in serum, which explains its significant neuropsychiatric effects 1:
- Anxiety
- Depression
- Psychosis
- Confusion
- Headaches
- Tremor
- Vertigo
- Dysarthria
- Seizures (increased risk in patients with alcohol-related hepatitis)
Other Common Side Effects
- Peripheral neuritis: May cause numbness or tingling in extremities 1
- Skin reactions: Allergic dermatitis may occur
- Gastrointestinal effects: Nausea, vomiting, and gastrointestinal disturbances
Monitoring Requirements
- Neuropsychiatric status should be assessed at least monthly and more frequently if symptoms develop 1
- Serum drug concentration measurements may be necessary until an appropriate dose is established
- For patients taking phenytoin, serum concentrations of phenytoin should be monitored due to potential interactions
Special Populations Considerations
Renal Impairment
- Cycloserine can accumulate in patients with impaired renal function 1
- Should not be used in patients with creatinine clearance <50 ml/minute unless they are receiving hemodialysis
- For hemodialysis patients, the dose should be 500 mg three times weekly or 250 mg daily
- Serum concentrations should be measured and dose adjusted accordingly
Hepatic Disease
- No specific dose adjustments needed except in patients with alcohol-related hepatitis who have an increased risk of seizures 1
Pregnancy
- Limited data on safety in pregnancy
- Should only be used when no suitable alternatives exist 1
Drug Interactions
- Patients taking phenytoin should have serum concentrations of phenytoin monitored
- Alcohol may worsen side effects and increase seizure risk
Practical Considerations
- Start with lower doses and titrate slowly to minimize neuropsychiatric side effects
- If severe neuropsychiatric symptoms develop, dose reduction or discontinuation may be necessary
- Patients should be educated about potential neuropsychiatric symptoms and advised to report them immediately
Pitfalls and Caveats
- Neuropsychiatric symptoms may be mistaken for worsening of underlying psychiatric conditions
- Failure to monitor patients regularly may lead to delayed recognition of serious adverse effects
- Patients with a history of psychiatric disorders may be at higher risk for neuropsychiatric side effects and require closer monitoring
Remember that cycloserine's neuropsychiatric effects are dose-dependent, and maintaining the lowest effective dose is important to minimize these adverse effects.