Thread: Which of the following drugs best crosses the blood-brain barrier?- Comprehension Questions

Comprehension Questions

[6.1] Which of the following drugs best crosses the blood-brain barrier?

A. Diphenoxylate
B. Kaolin
C. Loperamide
D. Methylcellulose

[6.2] Which of the following drugs inhibits the release of acetylcholine from cholinergic nerves in the submucosa and myenteric complex?

A. Cholestyramine
B. Docusate
C. Loperamide
D. Pectin

[6.3] Which of the following drugs shows an allergic cross reaction with an antibiotic?

A. Diphenoxylate
B. Octreotide
C. Psyllium
D. Sulfasalazine

Answers / Explanations:

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[6.1] A. Diphenoxylate can cross the blood-brain barrier and cause dependence. Methylcellulose and kaolin are not absorbed from the GI tract. Loperamide does not cross the blood-brain barrier.
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[6.2] C. The opioid loperamide inhibits release of acetylcholine from cholinergic nerves in the submucosa and myenteric complex to disrupt coordinated colonic motility and to increase water absorption and transit time through the GI tract. Pectin absorbs fluids in the gastrointestinal tract. Stool softeners like docusate increase the penetration of water and lipids into compacted fecal material.
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[6.3] D. Sulfasalazine is composed of 5-ASA and sulfapyridine. Sulfapyridine, which does not appear to play an active role in the reduction of inflammation in the colon, mediates an allergic cross reaction with sulfonamide drugs.
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PHARMACOLOGY PEARLS

• Antidiarrheal agents should not be used be used to treat patients experiencing bloody stools or high fever because of the increased risk of aggravating the underlying condition.
  
• Cholestyramine and colestipol bind excess diarrhea-causing bile salts.
  
• Many laxatives are commonly overused by the lay public.

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