Dose-related side effects
The most common side effects are neurotoxic and dose-related. They include:

• drowsiness
• diplopia
• headache
• ataxia
• nausea
• vomiting
• dizziness

These side effects tend to occur within a week of initiation or dosage increase. In chronic therapy, they typically are noticeable 3-4 hours after a dose (associated with peak serum concentrations).

They can be lessened by:

• reducing the total daily dosage
• splitting the total daily dosage into more frequent doses
• shifting more of the total daily dosage to bedtime, especially for patients with nocturnal or early-morning seizures
• switching to an extended-release form of carbamazepine, like Tegretol-XR or Carbatrol

Other systemic side effects include:

• abdominal pain
• constipation
• diarrhea
• loss of appetite

Hyponatremia is generally asymptomatic, though fluid retention, confusion, and increased seizures may signal symptomatic hyponatremia. In such cases, fluid restriction may be helpful. If symptomatic hyponatremia persists, discontinuation is warranted. Elderly patients and others with heart disease appear to be at particular risk for hyponatremia. Serum sodium should be checked before treatment and within the first month of treatment.

Adverse effects on cognition, memory, or mood generally are not commonly associated with carbamazepine.

To avoid possible bone loss associated with long-term use, patients should be advised to meet recommended requirements for vitamin D and calcium, expose their skin to sunlight in moderation, and engage in antigravity exercises.

Idiosyncratic reactions
Idiosyncratic reactions include a morbilliform rash in approximately 5-10% of patients. More serious rashes, such as Stevens-Johnson syndrome, photosensitivity, exfoliative dermatitis, and erythema multiforme, occur rarely.