Diazepam and Constipation
Yes, diazepam can cause constipation as a documented gastrointestinal adverse effect, though it is not among the most common side effects of this benzodiazepine. 1
Evidence for Diazepam-Induced Constipation
The FDA drug label for diazepam explicitly lists constipation under gastrointestinal adverse reactions, alongside nausea and other gastrointestinal disturbances 1. While the most commonly reported side effects are drowsiness, fatigue, muscle weakness, and ataxia, constipation represents a recognized secondary effect that clinicians should monitor.
Interestingly, one study examining diazepam's effects on gastrointestinal motility found that it actually enhanced gastric emptying and increased the amplitude of contractions during certain digestive phases 2. This seemingly contradictory finding highlights that benzodiazepines can have complex, variable effects on different segments of the GI tract—potentially slowing colonic transit while affecting gastric function differently.
Evaluation Steps
When a patient on diazepam presents with constipation:
1. Confirm Medication-Related Constipation
- Document temporal relationship: Did constipation begin or worsen after starting diazepam?
- Review all medications for constipating agents (opioids, anticholinergics, antidepressants, iron supplements, 5-HT3 antagonists) 3
- Assess for polypharmacy, especially in elderly patients who are five times more prone to constipation 3
2. Rule Out Secondary Causes
- Check for fecal impaction via digital rectal examination with assessment of pelvic floor motion during simulated evacuation 4
- Evaluate for alarm symptoms: blood in stool, unintentional weight loss, acute onset, anemia
- Laboratory testing: Complete blood count only (unless other symptoms warrant metabolic panel for calcium, glucose, thyroid-stimulating hormone) 4
- Do not perform colonoscopy unless alarm features present or age-appropriate screening overdue 4
3. Assess Constipation Severity
Look for Rome III criteria (≥2 of the following):
- Straining during >25% of bowel movements
- Lumpy or hard stools >25% of time
- Sensation of incomplete evacuation
- Sensation of anorectal blockage
- Manual maneuvers needed to defecate
- <3 spontaneous bowel movements per week 3
Management Algorithm
First-Line: Non-Pharmacological Measures
- Ensure privacy and comfortable toileting position (small footstool to assist)
- Increase fluid intake
- Increase activity/mobility within patient's limits
- Optimize timing: attempt defecation 30 minutes after meals, strain no more than 5 minutes 3
Second-Line: Laxative Therapy
Start with osmotic laxatives (preferred first choice):
- Polyethylene glycol (PEG) 17 g/day—excellent safety profile, especially for elderly 3
- Lactulose 30-60 mL daily 5
- Magnesium hydroxide 30-60 mL daily (avoid in renal impairment due to hypermagnesemia risk) 3
If inadequate response, add stimulant laxatives:
- Senna 2 tablets every morning (maximum 8-12 tablets/day) 5
- Bisacodyl 2-3 tablets PO daily 5
- Sodium picosulfate 3
Avoid bulk laxatives (psyllium, Metamucil) in patients with reduced mobility or low fluid intake—risk of mechanical obstruction 3
Third-Line: Rectal Interventions
If digital rectal exam identifies full rectum or fecal impaction:
Contraindications for enemas: neutropenia, thrombocytopenia, recent colorectal/gynecological surgery, recent pelvic radiotherapy, undiagnosed abdominal pain 3
Fourth-Line: Advanced Therapies
If constipation persists despite above measures:
- Lubiprostone (secretagogue)
- Linaclotide (secretagogue)
- Consider prokinetic agents (metoclopramide 10-20 mg PO TID) 5
Special Considerations
Elderly Patients on Diazepam
This population faces compounded risk due to:
- Diazepam's prolonged half-life (increases ~1 hour per year of age, starting at 20 hours at age 20) 1
- Increased volume of distribution and decreased clearance 1
- Polypharmacy effects
- Reduced mobility and hydration 3
Dosing caution: Limit to 2-2.5 mg once or twice daily initially in elderly to prevent oversedation and falls 1
Hepatic Impairment
Diazepam half-life increases 2-5 fold in cirrhosis (up to 500 hours reported), with decreased clearance by almost half 1. These patients require:
- Reduced diazepam dosing
- Cautious use of magnesium-containing laxatives (monitor for hypermagnesemia)
- Regular monitoring if on diuretics or cardiac glycosides (dehydration/electrolyte risk) 3
Clinical Pitfall
Do not assume diazepam is the sole culprit without comprehensive medication review—benzodiazepines cause constipation less frequently than opioids, anticholinergics, or certain antidepressants 3. However, when multiple constipating medications are present, consider whether diazepam can be tapered or substituted if clinically appropriate, rather than simply adding escalating laxative regimens.