# 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.