Senna is a stimulant laxative that retains water in the intestines, and docusate sodium is a stool softener that increases water in the stool, explains WebMD. The two products are taken orally to treat constipation. Side effects of senna and docusate sodium include nausea, abdominal pain and weakness.
Most products containing senna and docusate are taken with a full glass of water, and all directions included on the package should be followed, states WebMD. Dosage is based on treatment response, medical condition and age. It may take 6 to 12 hours for this medication to cause a bowel movement, and it is important to call a doctor if bleeding from the rectum occurs or the condition worsens. Senna with docusate typically is not taken for more than 7 days.