Constipation is a frequently reported problem often associated with unsatisfactory treatment. Despite investigations on many agents, there exists limited data to support their use. The present systematic review assessed the efficacy and safety of traditional medical therapies for chronic constipation and made evidence-based recommendations.

It searched the English literature for drug trials evaluating the treatment of constipation using MEDLINE and PUBMED databases from 1966 to 2003. It included randomized studies conducted on adult subjects and published as full manuscripts. It assigned a quality score to the studies based on published methodology and used Standard forms to abstract data regarding study design, duration, outcome measures, and adverse events. The review used the cumulative evidence of published data for each agent and made recommendations regarding their use based on the United States Preventive Services Task Force guidelines.

The review found-

• Good evidence (Grade A) supporting the use of polyethylene glycol (PEG) and tegaserod.
• Moderate evidence (Grade B) supporting the use of psyllium and lactulose. 
• A lack of quality data regarding many commonly used agents, including milk of magnesia, senna, bisacodyl, and stool softeners.

This systemic review describes good evidence to support the use of PEG, tegaserod, lactulose, and psyllium. Surprisingly, it found a paucity of trials for many commonly used agents. Thus, these aspects should be considered when designing trials comparing new agents with traditional therapies because their use may need to be better validated.

Ramkumar D, Rao SS. Efficacy and safety of traditional medical therapies for chronic constipation: a systematic review. Am J Gastroenterol. 2005 Apr;100(4):936-71. doi: 10.1111/j.1572-0241.2005.40925.x. PMID: 15784043.