As your mom has tested positive for stress test
she has a certain amount of blockage in vessels of her heart;presently she does not have any chest pain
so its ok;but also keep in mind diabetic patient sometimes do not have chest pain even if they have heart attack
due to neuropathy(that is decrease in sensation as a result of nerve damage
due to diabetes
).Calf muscle pain
is a sign of deep vein thrombosis
(DVT).So in both situations your mom requires blood thinner & better dosage according to the doctor may be 150 mg clopitab as he has seen your mother so he will decide better.As for your question on how long to take clopitab;the answer is as long as it is fet necessary by the treating doctor or even life long.Remember cardiac ;diabetic medicines are to be taken life long if they do not require discontinuation due to any cause so you can continue.Only precaution to be taken for your mom till she is on clopitab is that she should avoid any work where there is a chance that she may get injured & starts bleeding.If any problem occurs you can take her to a hospital & tell them what medicine she is taking.