Side effects from drugs often manifest themselves in the gastrointestinal system. If suffering from diarrhoea or constipation, the three-day rule applies: although these side effects can be unpleasant, you should avoid taking a remedy within three days. Drink liquids to replace fluid lost through diarrhoea. If it lasts more than three days, or is accompanied by a fever or by blood, pus or mucus, call your Pegasus doctor. 

Constipation is a more common and less serious side effect. This happens when a drug slows down the activity of the bowel. Drugs may also take moisture from the bowel, resulting in a more solid stool. Don't take laxatives within the first three days. Rather, drink up to 10 glasses of  water a day. Adding fibre to your diet and increasing exercise can also help.