Which of the following medications, excluding syp. lactulose (lactulose), can cause constipation in a patient taking pantoprazole (proton pump inhibitor)?

Pantoprazole Can Cause Constipation

Pantoprazole (a proton pump inhibitor) is the medication that can cause constipation in this scenario. While constipation is not the most common side effect of PPIs, it is a recognized adverse effect of this drug class, whereas lactulose is specifically used to treat constipation rather than cause it.

Mechanism and Evidence

Proton Pump Inhibitors and Constipation

• PPIs like pantoprazole are documented to cause constipation as an adverse effect 1.
• The mechanism involves alteration of gastrointestinal motility and changes in the gut microbiome secondary to acid suppression 2, 3.
• Constipation is listed among the reported side effects of omeprazole (another PPI in the same class as pantoprazole), along with nausea, vomiting, and diarrhea 4.

Clinical Context

• When assessing persistent constipation in patients, providers should evaluate all medications with the potential to cause constipation, including PPIs 1.
• Multiple drug classes beyond opioids can induce constipation, and PPIs are among the commonly prescribed medications that may contribute to this problem 2, 3.

Important Distinction: Lactulose Does NOT Cause Constipation

• Lactulose is an osmotic laxative specifically used to TREAT constipation, not cause it 1.
• Lactulose is a semi-synthetic disaccharide that produces osmotic diarrhea and is not absorbed from the gastrointestinal tract 1.
• Clinical studies demonstrate that lactulose produces statistically significant increases in stool frequency, weight, volume, and water content compared to placebo 5.
• Lactulose is recommended as a first-line treatment option for constipation in multiple clinical guidelines 1.

Clinical Pitfall to Avoid

• Do not confuse the adverse effects of acid-suppressing medications (like pantoprazole) with the therapeutic effects of laxatives (like lactulose) 1.
• When patients on PPIs develop constipation, consider whether the PPI itself may be contributing to the problem, especially if other constipating medications (such as opioids) are also present 1.