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Drug Interactions between HalfLytely and Bisacodyl and Synthroid

This report displays the potential drug interactions for the following 2 drugs:

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Interactions between your drugs

Moderate

sodium bicarbonate bisacodyl

Applies to: HalfLytely and Bisacodyl (bisacodyl / polyethylene glycol 3350 / potassium chloride / sodium bicarbonate / sodium chloride) and HalfLytely and Bisacodyl (bisacodyl / polyethylene glycol 3350 / potassium chloride / sodium bicarbonate / sodium chloride)

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.

References (1)
  1. Cerner Multum, Inc. "UK Summary of Product Characteristics."
Moderate

bisacodyl polyethylene glycol 3350

Applies to: HalfLytely and Bisacodyl (bisacodyl / polyethylene glycol 3350 / potassium chloride / sodium bicarbonate / sodium chloride) and HalfLytely and Bisacodyl (bisacodyl / polyethylene glycol 3350 / potassium chloride / sodium bicarbonate / sodium chloride)

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.

References (15)
  1. Cerner Multum, Inc. "UK Summary of Product Characteristics."
  2. Cerner Multum, Inc. "Australian Product Information."
  3. Baudet JS, Castro V, Redondo I (2010) "Recurrent ischemic colitis induced by colonoscopy bowel lavage." Am J Gastroenterol, 105, p. 700-1
  4. (2010) "Product Information. Suprep Bowel Prep Kit (magnesium/potassium/sodium sulfates)." Braintree Laboratories
  5. Ajani S, Hurt RT, Teeters DA, Bellmore LR (2012) "Ischaemic colitis associated with oral contraceptive and bisacodyl use." BMJ Case Rep, 2012
  6. (2016) "Product Information. MoviPrep (polyethylene glycol 3350 with electrolytes)." Physicians Total Care
  7. (2020) "Product Information. Plenvu (polyethylene glycol 3350 with electrolytes)." Bausch Health US (formerly Valeant Pharmaceuticals)
  8. (2022) "Product Information. GaviLyte-H and Bisacodyl with Flavor Packs (bisacodyl-PEG 3350 with electrolytes)." Gavis Pharmaceuticals
  9. "Product Information. Bi-Peglyte (bisacodyl-PEG 3350 with electrolytes)." Pendopharm
  10. Vaizman K, Li J, Iswara K, Tenner S (2007) "Ischemic colitis induced by the combination of Bisacodyl and polyethylene glycol in preparation for colonoscopy." Am J Gastroenterol, 102, S267
  11. Belsey J, Epstein O, heresbach D (2009) "Systematic review: adverse event reports for oral sodium phosphate and polyethylene glycol." Aliment Pharmacol Ther, 29, p. 15-28
  12. Hung SY, Chen HC, Chen WT (2020) "A randomized trial comparing the bowel cleansing efficacy of sodium picosulfate/magnesium citrate and polyethylene glycol/Bisacodyl (The Bowklean Study)" Sci Rep, 10, p. 5604
  13. Adamcewicz M, Bearelly D, Porat G, Friedenberg FK (2011) "Mechanism of action and toxicities of purgatives used for colonoscopy preparation." Expert Opin Drug Metab Toxicol, 7, p. 89-101
  14. Anastassopoulos K, Farraye FA, Knight T, Colman S, Cleveland MvB, Pelham RW (2016) "A comparative study of treatment-emergent adverse events following use of common bowel preparations among a colonoscopy screening population: results from a post-marketing observational study." Dig Dis Sci, 61, p. 2993-3006
  15. Barbeau P, Wolfe D, Yazdi F, et al. (2018) "Comparative safety of bowel cleansers: protocol for a systematic review and network meta-analysis." BMJ Open, 8, e021892

Drug and food interactions

Moderate

levothyroxine food

Applies to: Synthroid (levothyroxine)

ADJUST DOSING INTERVAL: Consumption of certain foods as well as the timing of meals relative to dosing may affect the oral absorption of T4 thyroid hormone (i.e., levothyroxine). T4 oral absorption is increased by fasting and decreased by foods such as soybean flour (e.g., infant formula), cotton seed meal, walnuts, dietary fiber, calcium, and calcium fortified juices. Grapefruit or grapefruit products may delay the absorption of T4 thyroid hormone and reduce its bioavailability. The mechanism of this interaction is not fully understood.

MANAGEMENT: Some manufacturers recommend administering oral T4 as a single daily dose, on an empty stomach, one-half to one hour before breakfast. In general, oral preparations containing T4 thyroid hormone should be administered on a consistent schedule with regard to time of day and relation to meals to avoid large fluctuations in serum levels. Foods that may affect T4 absorption should be avoided within several hours of dosing if possible. Consult local guidelines for the administration of T4 in patients receiving enteral feeding.

References (3)
  1. (2002) "Product Information. Synthroid (levothyroxine)." Abbott Pharmaceutical
  2. (2022) "Product Information. Armour Thyroid (thyroid desiccated)." Forest Pharmaceuticals
  3. Wohlt PD, Zheng L, Gunderson S, Balzar SA, Johnson BD, Fish JT (2009) "Recommendations for the use of medications with continuous enteral nutrition." Am J Health Syst Pharm, 66, p. 1438-67
Moderate

levothyroxine food

Applies to: Synthroid (levothyroxine)

ADJUST DOSING INTERVAL: Concurrent administration of calcium-containing products may decrease the oral bioavailability of levothyroxine by one-third in some patients. Pharmacologic effects of levothyroxine may be reduced. The exact mechanism of interaction is unknown but may involve nonspecific adsorption of levothyroxine to calcium at acidic pH levels, resulting in an insoluble complex that is poorly absorbed from the gastrointestinal tract. In one study, 20 patients with hypothyroidism who were taking a stable long-term regimen of levothyroxine demonstrated modest but significant decreases in mean free and total thyroxine (T4) levels as well as a corresponding increase in mean thyrotropin (thyroid-stimulating hormone, or TSH) level following the addition of calcium carbonate (1200 mg/day of elemental calcium) for 3 months. Four patients had serum TSH levels that were higher than the normal range. Both T4 and TSH levels returned to near-baseline 2 months after discontinuation of calcium, which further supported the likelihood of an interaction. In addition, there have been case reports suggesting decreased efficacy of levothyroxine during calcium coadministration. It is not known whether this interaction occurs with other thyroid hormone preparations.

MANAGEMENT: Some experts recommend separating the times of administration of levothyroxine and calcium-containing preparations by at least 4 hours. Monitoring of serum TSH levels is recommended. Patients with gastrointestinal or malabsorption disorders may be at a greater risk of developing clinical or subclinical hypothyroidism due to this interaction.

References (4)
  1. Schneyer CR (1998) "Calcium carbonate and reduction of levothyroxine efficacy." JAMA, 279, p. 750
  2. Singh N, Singh PN, Hershman JM (2000) "Effect of calcium carbonate on the absorption of levothyroxine." JAMA, 283, p. 2822-5
  3. Csako G, McGriff NJ, Rotman-Pikielny P, Sarlis NJ, Pucino F (2001) "Exaggerated levothyroxine malabsorption due to calcium carbonate supplementation in gastrointestinal disorders." Ann Pharmacother, 35, p. 1578-83
  4. Neafsey PJ (2004) "Levothyroxine and calcium interaction: timing is everything." Home Healthc Nurse, 22, p. 338-9

Therapeutic duplication warnings

No warnings were found for your selected drugs.

Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.

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Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

Further information

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