Carbamazepine - Adverse Effects

Adverse Effects

Common adverse effects may include drowsiness, headaches and migraines, motor coordination impairment, and/or upset stomach. Carbamazepine preparations typically greatly decrease a person's alcohol tolerance.

Less common side-effects may include cardiac arrhythmias, blurry or double vision and/or the temporary loss of blood cells or platelets and in rare cases can cause aplastic anemia. With normal use, small reductions in white cell count and serum sodium are common; however, in rare cases, the loss of platelets may become life-threatening. In this case a doctor may recommend frequent blood tests during the first few months of use, followed by three to four tests per year for established patients. Additionally, carbamazepine may possibly exacerbate preexisting cases of hypothyroidism, so yearly thyroid function tests are advisable for persons taking the drug.

There are also rare reports of an auditory side-effect for carbamazepine use, whereby patients perceive sounds about a semitone lower than previously. Thus, middle C would be heard as the note B₃ just below it, and so on. The inverse effect (that is, notes sounding higher) has also been recorded. This unusual side-effect is usually not noticed by most people, and quickly disappears after the person stops taking carbamazepine.

Carbamazepine increases the risk of developing lupus by 88% (odds ratio of 1.88), with the effect possibly restricted to women.

Oxcarbazepine, a derivative of carbamazepine, reportedly has fewer and less serious side-effects.

Carbamazepine may cause syndrome of inappropriate antidiuretic hormone (SIADH), since it both increases the release and potentiates the action of ADH (vasopressin).

Carbamazepine may aggravate juvenile myoclonic epilepsy, so it is important to uncover any history of jerking, especially in the morning, before starting the drug. It may also aggravate other types of generalized seizure disorder, particularly absence seizures.

In addition, carbamazepine has been linked to serious adverse cognitive anomalies, including EEG slowing and apoptosis of cultured cerebellar neurons.

The FDA informed health care professionals that dangerous or even fatal skin reactions (Stevens–Johnson syndrome and toxic epidermal necrolysis), that can be caused by carbamazepine therapy, are significantly more common in patients with a particular human leukocyte antigen (HLA) allele, HLA-B*1502. This allele occurs almost exclusively in patients with ancestry across broad areas of Asia, including South Asian Indians. In Europeans a large proportion of sensitivity is associated with HLA-B58. Researchers have also identified another genetic variant, HLA-A*3101 which has been shown to be a strong predictor of both mild and severe adverse reactions to carbamazepine among Japanese and Europeans.