5-step plan to treat constipation in psychiatric patients
Algorithm can individualize treatment when drugs or other factors are binding.
- older tricyclic antidepressants (such as amitriptyline)
- antipsychotics.
Outlet obstruction, caused by inappropriately contracting posterior pelvic floor muscles during defecatory effort, is the cause of 5% to 10% of constipation cases.1 Patients are not aware of this pelvic floor incoordination. Often, they will give a history of straining even for soft or liquid stool.
Consider outlet obstruction in women with history of multiple vaginal childbirths or pelvic or gynecologic surgery, particularly if they fail to respond to usual measures to treat constipation. For adequate relief, these patients often require anorectal biofeedback, which teaches them to relax the posterior pelvic floor.11,12
Habitually suppressing the gastrocolic reflex—the urge to defecate after eating—causes some patients difficulty moving their bowels. Counsel these patients to sit on the toilet for several minutes after the morning meal to relearn this behavior. Some may need several weeks of daily enema or glycerine suppository use to retrain themselves to have bowel movements after the morning meal.
Other psychiatric-related causes. Patients with depression may experience decreased stool output because of a lack of food intake or physical activity. These causes may be effectively addressed by treating the depression.
Give special consideration to patients with eating disorders and those who routinely use laxatives. A patient who is not eating will not produce the same amount of stool as one who eats regularly.
Constipated patients may require escalating doses of laxatives to obtain symptom relief; this does not constitute laxative abuse but rather tachyphylaxis. Chronic laxative use has not been shown to permanently decrease colonic motility,14 but patients who use laxatives chronically may have altered expectations of what is normal.
CASE CONTINUED: Recurring symptoms
After discontinuing Mr. W’s olanzapine and duloxetine, the psychiatrist prescribes polyethylene glycol solution (MiraLax) and instructs Mr. W to increase his daily fluid and fiber intake. Although the solution works well, Mr. W complains of the cost. He then resumes methyl cellulose and starts taking magnesium hydroxide chewable tablets (Milk of Magnesia) every 2 to 4 days as needed for constipation.
The psychiatrist prescribes mirtazapine for OCD symptoms, but soon stops this regimen because Mr. W complains of worsening constipation. Next Mr. W is started on fluvoxamine, which he had tried briefly many years before. The dosage is gradually titrated to 150 mg/d. Although Mr. W’s OCD improves somewhat, he complains of agitation and once again of worsening constipation.
Treatment algorithm
To minimize trial and error, we use a stepwise approach to treating constipation (Algorithm).8,11,15 Although many standard recommendations have not been evaluated in large randomized controlled trials, they are supported by decades of observed actions among clinicians and thus remain valuable.
Multiple nonprescription agents are available to treat constipation, including:
- bulking agents (fiber supplements)
- lubricating agents
- stool softening agents
- stimulant and osmotic laxatives (Table 2).8
Steps 1 & 2. When initial attempts at increasing physical activity, fluid, and dietary fiber fail to yield a response, fiber supplements are commonly used as a second step in managing constipation. We advocate beginning with a supplement that contains psyllium—such as Fiber-all or Metamucil—because psyllium has been shown to increase stool frequency. Supplements that contain methylcellulose (Citrucel), polycarbophil (such as Equalactin and Mitrolan), or bran have either not shown efficacy or have not been studied rigorously enough to merit recommendation.10 Some patients respond to other fiber products, but start a fibernaïve patient with a psyllium-containing supplement.
Fiber supplements may cause increased gas and bloating, so start at a low dose and gradually increase over several weeks to mitigate these side effects.
