The average adult dosage of the laxative bisacodyl for constipation is 5 to 15 mg, or 1 to 3 tablets orally once a day, as needed. The average adult dose for constipation when inserted rectally is 10 mg, or one suppository per day as needed, explains Drugs.com.
When not in suppository form, bisacodyl is also available as a liquid that can be inserted rectally. The average adult dosage of bisacodyl for constipation as a liquid enema is also 10 mg, according to Drugs.com. Patients with impaired renal function are advised to use bisacodyl cautiously as the monobasic or dibasic sodium phosphate contained within can lead to further complications.