Hi Every drug has some side effects and not all people will get all the side effects. Glimestar produces following side effects : Sore throat, muscle pain, weight gain, or tooth problems may occur. If any of these effects persist or worsen, notify your doctor or pharmacist promptly.Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.Tell your doctor right away if either of these serious side effects occurs: new/worsening vision problems (such as blurred vision), bone fracture.Pioglitazone may rarely cause liver disease. Tell your doctor right away if you develop symptoms of liver disease, including: dark urine, yellowing of eyes/skin, persistent nausea/vomiting, stomach/abdominal pain.Pioglitazone does not usually cause low blood sugar (hypoglycemia). Low blood sugar may occur if this drug is prescribed with other anti-diabetic medications (such as insulin or a sulfonylurea). But more important in your case is whether a biopsy was taken from the rectal thickening and what was the final report. You please try to find it out before proceeding. All the best. Dr. Mohammed Ibrahim Surgical Oncologist mdibrahimdr@yahoo.co.in