HI Well come to HCM I really appreciate your concern, if this is the constipation and your taking senna and other medication for that so I would advise you to stop these and try to eat more fiber containing diet, drink more water, keep the regular habit of going for defecation even in absent of need of this, no matter if you do not pass the stool still be inside and sit for while, no need to be over conscious if you do not pass the stool. Purgative and laxative may not cause the melanosis, but it is better to avoid if the constipation is due to lack of water and less fiber diet taken hope this information helps.