Drug Interactions between disopyramide and HalfLytely and Bisacodyl

CONTRAINDICATED: The following interaction does not apply to all products containing potassium chloride, including split dose products used for colon preparation prior to colonoscopy. It is applicable to certain oral solid formulations of potassium chloride used primarily for potassium supplementation, and the prescriber should consult the individual product labeling for more specific information and guidance.

Concomitant use of agents with anticholinergic properties (e.g., antihistamines, antispasmodics, neuroleptics, phenothiazines, skeletal muscle relaxants, tricyclic antidepressants, the class IA antiarrhythmic disopyramide) may potentiate the risk of upper gastrointestinal injury associated with oral solid formulations of potassium chloride. The proposed mechanism involves increased gastrointestinal transit time due to reduction of stomach and intestinal motility by anticholinergic agents, thereby creating a high localized concentration of potassium ions in the region of a dissolving tablet or capsule and increasing the contact time with GI mucosa. Solid formulations of potassium chloride have been associated with upper GI bleeding and small bowel ulceration, stenosis, perforation, and obstruction. Deaths have been reported rarely. In clinical studies, short-term coadministration of wax-matrix or microencapsulated formulations of potassium chloride at high dosages in combination with an anticholinergic agent such as glycopyrrolate resulted in more frequent and more serious endoscopic lesions than potassium therapy alone. However, the lesions were not accompanied by bleeding or epigastric symptoms. Some investigators have suggested a higher risk of upper GI lesions with wax-matrix than microencapsulated formulations, although existing data are limited and conflicting.

MANAGEMENT: The use of certain oral solid formulations of potassium chloride is considered contraindicated in patients receiving agents with anticholinergic properties at sufficient doses to exert anticholinergic effects. A liquid formulation of potassium chloride should be considered. Patients prescribed a solid oral formulation should be advised to discontinue potassium therapy and contact their physician if they experience potential symptoms of upper GI injury such as severe vomiting, abdominal pain, distention, and gastrointestinal bleeding.

MONITOR: Bowel cleansing as well as overuse of certain laxatives may cause electrolyte loss and increase the risk of torsade de pointes ventricular arrhythmia in patients treated with drugs that prolong the QT interval. Electrolyte disturbances including hypokalemia and hypomagnesemia have been reported with laxative abuse and are known risk factors for torsade de pointes associated with QT interval prolongation.

MANAGEMENT: Patients treated with drugs that prolong the QT interval should exercise caution when self-medicating with laxatives. The recommended dosage and duration of use should not be exceeded. Patients treated with lactulose for more than six months should be monitored periodically for electrolyte imbalance. Patients should be advised to seek prompt medical attention if they experience symptoms that could indicate the occurrence of torsade de pointes such as dizziness, lightheadedness, fainting, palpitation, irregular heart rhythm, shortness of breath, or syncope.

MONITOR: Bowel cleansing as well as overuse of certain laxatives may cause electrolyte loss and increase the risk of torsade de pointes ventricular arrhythmia in patients treated with drugs that prolong the QT interval. Electrolyte disturbances including hypokalemia and hypomagnesemia have been reported with laxative abuse and are known risk factors for torsade de pointes associated with QT interval prolongation.

MANAGEMENT: Patients treated with drugs that prolong the QT interval should exercise caution when self-medicating with laxatives. The recommended dosage and duration of use should not be exceeded. Patients treated with lactulose for more than six months should be monitored periodically for electrolyte imbalance. Patients should be advised to seek prompt medical attention if they experience symptoms that could indicate the occurrence of torsade de pointes such as dizziness, lightheadedness, fainting, palpitation, irregular heart rhythm, shortness of breath, or syncope.

ADJUST DOSING INTERVAL: By increasing gastric pH, antacids may reduce the resistance of the enteric coating of bisacodyl tablets, resulting in earlier release of bisacodyl and gastric irritation and dyspepsia.

MANAGEMENT: The administration of antacids and bisacodyl should be separated by at least one hour.

GENERALLY AVOID: Concomitant use of stimulant laxatives (e.g., bisacodyl, sodium picosulfate) may increase the risk of serious gastrointestinal adverse effects associated with certain osmotic laxatives (e.g., polyethylene glycol (PEG), oral sulfate solution), such as colonic mucosal ulcerations or ischemic colitis. There have been isolated case reports of ischemic colitis occurring with the use of PEG-based bowel cleansing products in combination with higher dosages of bisacodyl (usually greater than 10 mg). Bisacodyl can cause colonic ischemia due to transient reduction in splanchnic blood flow. When administered in conjunction with an osmotic laxative such as PEG, increased intramural pressure secondary to increased peristalsis may lead to ischemic colitis and perforation.

MANAGEMENT: The manufacturers for some osmotic bowel cleansing products recommend avoiding the concurrent use of stimulant laxatives. However, stimulant laxatives, in particular bisacodyl and sodium picosulfate, are sometimes used with PEG in certain bowel cleansing regimens to help reduce dose volume and improve patient tolerability and acceptance. Please consult individual product labeling for specific recommendations and guidance. Patients using osmotic bowel cleansing products and stimulant laxatives who present with sudden abdominal pain, rectal bleeding, or other symptoms of ischemic colitis should be evaluated promptly.