22 - Weight related effects

Weight related effects

© SPMM Course Valproate can cause obesity, hyperandrogenism and PCOD associated with hirsutism. Anticonvulsant hypersensitivity syndrome is seen in 0.1% of patients taking anticonvulsants. Aromatic compounds (lamotrigine, carbamazepine, phenytoin and phenobarbitone) are especially risky. 5 to 20% of those taking aromatic anticonvulsants will experience a rash. Lamotrigine can cause a rash in 10% of patients. Risk factors for rash include rapid initial dose escalation, concurrent VPA, and age less than 16 years. As benign rashes cannot be distinguished from potentially serious ones, any rash requires discontinuation of the drug. Lamotrigine carries a significant risk of Steven Johnson Syndrome (SJS – risk of 1 in 3000) especially if administered together with Valproate as the enzyme inhibiting effects of Valproate may increase lamotrigine levels. SJS starts with a rash, pharyngitis and fever. Systemic involvement follows quickly if the drug is not stopped.

Drug Dose-related effects Idiosyncratic reactions Carbamazepine Visual disturbances, GI disturbances, cognitive impairment, vertigo and, dizziness. Hematological reactions including agranulocytosis or aplastic anemia, idiosyncratic Stevens-Johnson syndrome, fulminant hepatic damage, and pancreatitis. SIADH is more common in the elderly Valproate Hyperammonemia, Teratogenicity, Sedation, Thrombocytopenia Hepatotoxicity, pancreatitis, rash and rarely acute dermatitis.

Weight related effects Weight gain is common (70% of those taking valproate and 40% of those taking carbamazepine over 12 months will experience weight gain); valproate induced weight gain is considered to be due to impaired beta-oxidation of fatty acids, and thus independent of calorie intake. Lamotrigine is often weight neutral Topiramate is weight neutral and can even cause weight loss. Topiramate can be potentially used to counteract the weight gain caused by many psychotropic drugs.