The doctor may advise you to take laxatives if you have medical conditions that may be worsened by straining. These conditions include heart disease, hemorrhoids and hernia rupture. Laxatives are also used to evacuate your bowel before you undergo lower abdominal medical procedures such as colonoscopy. Oral laxatives should be taken one or two hours after meals. Different types of oral laxatives include bulk-forming laxatives, saline laxatives, lubricant laxatives and stimulant laxatives. Oral laxatives should be taken after meals with a full glass of cold water or juice, according to Drugs.com.