Carcinoid Syndrome & VIPomas

Peripheral Treatments

Peripheral treatments, though they do not address the causes of hormonal hypersecretion, may provide beneficial relief of the symptoms of carcinoid syndrome.

• Antidiarrheal Agents
  • Antimotility Agents
  • Adsorbent Agents
  • Antisecretory Agents
  • Bacterial Replacement Agents
• Other Peripheral Treatments
  • Experimental Drugs

Antidiarrheal Agents

A variety of different pharmacologic agents have been used to treat diarrhea. Antidiarrheals can be divided into three main categories, depending on their mode of action: antimotility agents, adsorbent agents, and antisecretory agents.

Antimotility Agents

• Atropine
• Diphenoxylate (e.g., Lomotil®, GD Searle & Co)
• Loperamide (Imodium®, Janssen Pharmaceutical Inc)
• Paregoric (e.g., Paregoric USP, Barre-National Inc)
• Opium tincture, "DTO" (deodorized tincture of opium) (Parepectolin®, Rhône-Poulenc Rorer Pharmaceuticals Inc.)

Characteristics:

• Reduce propulsive activity of the gut and thus reduce stool frequency and volume in most patients (2).
• Slow transit time (contact between intraluminal contents and the intestinal mucosa increases), thereby enhancing the potential for absorption (2).
• Potential risk of addiction if diarrhea is chronic and the agent must be used for prolonged periods (1).

Adsorbent Agents (1)

• Kaolin-pectin mixture (e.g., Kaopectate®, The Upjohn Company
• Kaolin-Pectin Suspension, Roxane Laboratories, Inc)
• Polycarbophil (e.g., Mitrolan® Tablets, AH Robins Company)

Characteristics:

• Nonspecific agents that act by binding intraluminal contents through surface adhesion.
• Generally, do not require a prescription.
• Indicated for symptomatic relief and may have limited value in chronic diarrhea.
• Bind intraluminal contents indiscriminately - toxins, digestive secretions, nutrients, and drugs.

Antisecretory Agents (1)

• Bismuth subsalicylate (Pepto-Bismol®, Procter & Gamble)

Characteristics:

• Contain ingredients that are toxic at high doses.
• Excipients such as salicylates can cause nausea, vomiting, and tinnitus, and can interfere with blood coagulation.
• Bismuth also poses a risk for toxicity at high doses.

Bacterial Replacement Agents

• Lactobacillus acidophilus (Bacid® Capsules, Fisons Corporation)
• Lactobacillus bulgaricus and L. acidophilus (Lactinex® Tablets and Granules, Hynson, Westcott & Dunning Products)

Other Peripheral Treatments

Agents such as diuretics, selective bronchodilators, and serotonin receptor blockers may be used to control the symptoms of carcinoid syndrome.

Experimental Drugs (1)

• Alpha-adrenergic agonists that promote absorption or prevent secretion.
• Beta-blockers
• Calcium channel blockers
• Phenothiazines
• Anti-inflammatory agents
• Enkephalin analogues (i.e., nifalatide, enkephalinase inhibitors)
• Vaccines (i.e., cholera, shigellosis)