Monday Pharmaceutical Mystery: April 6


What are you going to recommend for a customer who was unable to complete a previously recommended regimen?

You are a retail pharmacist, filling prescriptions. It’s a busy day due to the coronavirus disease 2019 (COVID-19). There is a line of cars at the drive through window, and the phone is ringing nonstop. A technician informs you that one of the customers at the window asked for you by name and wants to talk to you regarding bowel preparation instructions you gave to her husband last week for his colonoscopy.

You recall the situation. (He was having nausea and vomiting midway through drinking the 4000 ml polyethylene glycol (PEG) with electrolytes bowel prep. You recommended he take a break and finish the rest in the morning according to the guidelines for the “Split dosing method.”)

Using the window phone, you ask how you can be of assistance. The customer thanks you for recommending the split dosing regimen for her husband last week, but unfortunately he was unable to complete the regimen due to a severe gag reflex triggered by the taste of the PEG with electrolytes, and the prior failed attempts.

She says that he is now having GI symptoms that need to be resolved with an emergency coloscopy. They are going back to the doctor today and was wondering if you could recommend another bowel regimen that they could ask the doctor about.

Mystery: What are you going to recommend now?

Solution: A bowel prep with PEG 3350 and without electrolytes (MiraLAX) could be a solution, and there are many regimens that do not involve PEG with electrolytes (GoLYTELY). However, these regimens may or may not be approved by the FDA.

Split dosing, low volume PEG without electrolytes usually involves 238-255 grams of powder mixed with 2 liters of a sugar free sports drink with electrolytes. It also may involve 2-4 pills of bisacodyl (Dulcolax) and a clear liquid diet 2-3 days prior to the test.

Patients are instructed to take bisacodyl 10 mg (two 5 mg tablets) at noon. Once the patient has a bowel movement, or after a maximum of 6 hours, the patient takes 240 mL of the PEG 3350 solution every 10 to 15 minutes until 2 liters are consumed. If split dosing is being used, 1 liter is taken in the evening before the colonoscopy and 1 liter is taken 6 hours prior to the procedure.

People who are high risk for electrolyte imbalances or have inflammatory bowel disease should be cautious of using bisacodyl and/or magnesium citrate. Exacerbation of inflammation, bowel necrosis, and electrolyte imbalances are all a concern. Also a concern is electrolyte imbalances and fluid overload.

Ultimately, it’s up to the doctor to choose a regimen that he or she feels comfortable with and is right for the patient.


Bechtold ML, Mir F, Puli SR, Nguyen DL. Optimizing bowel preparation for colonoscopy: a guide to enhance quality of visualization. Ann Gastroenterol. 2016;29(2):137—146. doi:10.20524/aog.2016.0005

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