Does Clonidine Cause Constipation?
Yes, clonidine does cause constipation as a documented adverse effect, occurring in approximately 10% of patients according to FDA labeling data. 1
Constipation as a Recognized Side Effect
Constipation is explicitly listed in the FDA drug label for clonidine as one of the most frequent dose-related adverse effects, affecting about 10 in 100 patients (10%). 1
The FDA label categorizes constipation among the common adverse reactions alongside dry mouth (40%), drowsiness (33%), dizziness (16%), and sedation (10%). 1
More severe gastrointestinal effects have also been reported, including pseudo-obstruction (including colonic pseudo-obstruction), though these are less frequent complications. 1
Mechanism and Clinical Context
Clonidine's constipating effect is consistent with its mechanism as a central alpha-2 adrenergic agonist, which reduces sympathetic tone and affects gastrointestinal motility. 2
The European Society of Cardiology guidelines specifically note that non-dihydropyridine calcium channel blockers like verapamil are contraindicated in patients ≥75 years with chronic constipation, and recommend treating constipation when it occurs—this same vigilance should apply to clonidine given its constipating properties. 3
Interestingly, clonidine has been used therapeutically to reduce diarrhea in specific clinical contexts (diabetic diarrhea, short bowel syndrome, fecal incontinence) by slowing intestinal transit and reducing intestinal secretions, which demonstrates its capacity to affect bowel function in the direction of constipation. 3, 4, 5, 6
Clinical Implications
When prescribing clonidine for hypertension or other indications, patients should be counseled about the 10% risk of developing constipation. 1
The American College of Cardiology positions clonidine as a last-line antihypertensive agent due to significant CNS adverse effects, and constipation adds to its unfavorable side effect profile. 2
In elderly patients (≥75 years), who are already at higher risk for constipation and its complications, the constipating effect of clonidine should be factored into prescribing decisions, particularly given this population's increased vulnerability to orthostatic hypotension and falls with clonidine use. 3, 2
Important Caveat
- While constipation is a recognized side effect, the FDA label notes that "in many cases patients were receiving concomitant medication and a causal relationship has not been established" for some less frequent adverse effects—however, constipation is listed among the most frequent dose-related effects where causality is more clearly established. 1