Respected user, hi I evaluated your query thoroughly. * Side effect of capsule effexor include diarrhea not loss of control on bowel movements , so this is an entity not related to effexor * She needs to get evaluated by thorough clinical examination with per rectal examination of anal sphincter tone, Proctoscopy & if required Colonoscopy in selected cases. * Unless the reason is found, treatment can not be figured out . Hope this helps you. Welcome for any further queries. Thanks for using Health care magics and giving me an opportunity to assist Wishing fine recovery from the same. Regards dear take care.