Is urinary retention a known side effect of lamotrigine?/nFor two years, a 17-year-old boy with Bec

Fråga: Is urinary retention a known side effect of lamotrigine?

For two years, a 17-year-old boy with Becker´s muscular dystrophy and seizures has been treated with lamotrigine. During this period of time he has experienced difficulties passing urine. The problems resolved when lamotrigine was temporarily withdrawn.

Sammanfattning: Theoretically, lamotrigine could interfere with neuronal control of bladder function by its inhibitory effects on excitatory amino acid release and there are a few case reports of urinary retention in lamotrigine treated patients.

Svar: We found no reports of lamotrigine-induced urinary retention in Drugline, Medline or standard pharmacological literature.

In the Swedish adverse drug reactions register (Swedis) there is one report of urine retention with a possible connection to lamotrigine treatment. One week after commencing lamotrigine medication, a 44-year-old epileptic experienced urinary incontinence and was diagnosed with urinary retention (residual urine volume 650 mL). Lamotrigine was withdrawn but the outcome of this dechallenge is unknown. In the register, there are two additional cases of enuresis in children treated with lamotrigine, with a possible causal relationship to the drug. However, the possibility of urinary retention with over-flow incontinence is not mentioned in these reports. (1)

In the WHO adverse drug reaction register (Vigibase), there are 11 reports of urinary retention in patients treated with lamotrigine, and another 40 cases of incontinence, nocturia and micturition disorders. However, due to differences in the reporting systems a causal relationship to lamotrigine medication cannot be established. (2)

Lamotrigine exerts its anti-epileptic effect by inhibiting neural release of excitatory amino acids, predominantly glutamate (3). Glutamate injections into the periaqueductal gray evokes bladder contraction in rats (4), and intrathecal administration of a broad-spectrum excitatory amino acid antagonist inhibits bladder contraction in cats (5). Hence, it is theoretically possible that lamotrigine could have an inhibitory effect on urinary bladder emptying by modulating excitatory neurotransmission.

We found no indications of urinary retention being a symptom of Becker´s muscular dystrophy per se and suggest this case be reported to the regional adverse drug reaction monitoring centre. Swedis (The Swedish Drug Information System) (cited 2005-04-07) Vigibase (The WHO adverse drug reactions database) (cited 2005-04-21) Lamictal. Summary of product characteristics (SPC) (GlaxoSmithKline AB) Matsuura S, Downie JW, Allen GV. Micturition evoked by glutamate microinjection in the ventrolateral periaqueductal gray is mediated through barrington´s nucleus in the rat. Neuroscience 2000;101;1053-61. Iwabuchi N. Sacral glutamatergic transmission in the descending limb of the micturition reflex in the cat. Fukuoka Igaku Zasshi 1997;88(2):30-8. (abstract)