Final answer:
Cisapride is a drug that can treat opioid-induced gastric stasis by increasing gastrointestinal motility. It is not effective in the presence of anticholinergic substances like atropine, and it increases lower esophageal sphincter tone rather than decreasing it.
Step-by-step explanation:
Cisapride is a medication that has historically been used to increase gastrointestinal motility. In answering the question, regarding the effects of cisapride, option B is correct: cisapride can be used to treat opioid-induced gastric stasis. Opioids are known to reduce gastric motility, leading to constipation and gastric stasis. Cisapride works by enhancing the release of acetylcholine at the myenteric plexus, which in turn stimulates gastrointestinal motility and can counteract the effects of opioids.
Option A is incorrect because cisapride's prokinetic effect could be blunted in the presence of atropine, which is an anticholinergic substance that would inhibit the action of acetylcholine. Option C is also incorrect, as cisapride does not decrease but rather increases lower esophageal sphincter tone, which can help prevent gastroesophageal reflux. Regarding option D, cisapride does not reduce gastric pH; it rather promotes gastric emptying without significantly altering gastric secretions. Lastly, for option E, cisapride does not increase gastric volume; instead, it enhances motility and hastens gastric emptying.