Lamotrigine-Induced Rash After Sun Exposure
To the Editor: Lamotrigine is an antiglutamatergic agent that promises treatment of bipolar disorder (1), especially in cases of bipolar depression (2). The main adverse effect of lamotrigine is skin eruption, which occurs in about 5% of treated patients and can in rare instances be severe (3). There are sparse reports in the literature of the occurrence of Stevens-Johnson syndrome (3) and toxic epidermal necrolysis (4). We present two cases of rashes appearing some time after the onset of lamotrigine administration.
Mr. A, a 42-year-old man with a diagnosis of schizoaffective disorder, bipolar type, was hospitalized in our clinic after a recurrence of his disorder that was induced by discontinuing his drug therapy. He received lamotrigine, 25 mg t.i.d., coadministrated with haloperidol, 20 mg b.i.d. His dose of lamotrigine was titrated gradually within a month. One year later, during Mr. A’s last hospitalization, his dose of lamotrigine was raised to 100 mg b.i.d., whereas his dose of haloperidol stayed the same. He showed a marked regulation of his mood fluctuations after his discharge, and he also experienced a relatively satisfying vocational and social adjustment. Three months later, an acute maculopapular rash with itching appeared, which subsided after his lamotrigine treatment was interrupted. The day before the rash appeared, he had been exposed to sunlight while doing agricultural work.
Ms. B, a 30-year-old woman with a diagnosis of bipolar disorder type I (her most recent episode was manic), received lamotrigine as a prophylactic therapy. Her lamotrigine dose was titrated gradually within 1 month up to 100 mg b.i.d.. Six months later, while her mood had a normal fluctuation, she developed an acute maculopapular rash with itching. The day before the rash appeared, she had been exposed to the light of a solarium. The rash subsided after her treatment with lamotrigine was discontinued.
In these cases, the absence of a history of skin disease and the subsidence of the rash after the discontinuation of lamotrigine lead to the conclusion that the rash was a side effect of the drug. In the first case, we presume that it was probably related to insolation because of Mr. A’s vocational activities. (He was a farmer.) In the second case, we conclude that it was related to exposure to the intense light of a solarium. The appearance of the rash, therefore, could be considered a delayed reaction to lamotrigine therapy, in combination with a stimulating factor (insolation). These findings lead us to propose that patients who receive lamotrigine should avoid prolonged exposure to sunlight.
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