Hi, Cremaffin-plus is an osmotic laxative commonly used for the symptomatic relief of constipation. Its common side effects include habit forming, loose motions, abdominal discomfort, muscle weakness, and on prolonged use it may cause deficiency of fat soluble vitamins and aspiration pneumonia. It is not associated with weight gain. Weight gain could be due to lack of exercise, hormonal diseases or other conditions for which you need to consult your doctor. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Mohammed Taher Ali, General & Family Physician