MIRALAX
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MIRALAX (MIRALAX).
Polyethylene glycol 3350 (PEG 3350) is an osmotic laxative that works by retaining water in the stool through hydrogen bonding, increasing fecal water content and promoting bowel movements.
| Metabolism | PEG 3350 is not metabolized; it is excreted unchanged in feces. |
| Excretion | Primarily excreted unchanged in feces (>90% of oral dose); negligible renal elimination (<0.1% recovered in urine). |
| Half-life | Not applicable; polyethylene glycol 3350 is minimally absorbed and systemic half-life is not clinically relevant. |
| Protein binding | Minimal to no protein binding due to negligible systemic absorption. |
| Volume of Distribution | Not applicable due to negligible absorption; localized to gastrointestinal tract. |
| Bioavailability | Negligible oral bioavailability (less than 0.01%) as the drug is not absorbed from the gastrointestinal tract. |
| Onset of Action | Oral: 24-48 hours for bowel movement in constipation; for colonoscopy prep, onset of watery stools within 1-3 hours. |
| Duration of Action | Duration of laxative effect is typically 24-48 hours after a single dose; full bowel cleansing for colonoscopy lasts until procedure. |
17 g (1 heaping tablespoon) dissolved in 4–8 oz of water, juice, soda, coffee, or tea, administered orally once daily. Maximum duration of use: 7 days.
| Dosage form | FOR SOLUTION |
| Renal impairment | No dosage adjustment required for mild to moderate renal impairment (GFR 30–89 mL/min). For severe renal impairment (GFR <30 mL/min) or dialysis-dependent patients, use with caution due to potential for electrolyte disturbances; consider reduced starting dose (e.g., 8.5 g daily) and monitor for adverse effects. |
| Liver impairment | No specific guidelines for Child-Pugh classification. Use with caution in severe hepatic impairment due to potential for altered fluid and electrolyte balance. No dose adjustment recommended but clinical monitoring advised. |
| Pediatric use | Children 6 months to <1 year: 4.25 g (1/4 packet) once daily. Children 1 to <6 years: 8.5 g (1/2 packet) once daily. Children 6 to <12 years: 17 g (1 packet) once daily. Dissolve in 4–8 oz of liquid. Maximum duration: 7 days. Not recommended for children <6 months. |
| Geriatric use | No specific dose adjustment. Use with caution in patients >65 years due to increased risk of electrolyte imbalance and dehydration. Consider initiating with lower doses (e.g., 8.5 g daily) and ensure adequate fluid intake. Monitor for adverse effects, particularly if using for more than a few days. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for MIRALAX (MIRALAX).
| Breastfeeding | Polyethylene glycol 3350 is not absorbed systemically following oral administration, thus it is not expected to be excreted into breast milk. M/P ratio is not applicable. Considered compatible with breastfeeding. |
| Teratogenic Risk | MIRALAX (polyethylene glycol 3350) is considered non-teratogenic based on animal studies and human data. No increased risk of congenital malformations has been reported. Risk in all trimesters is minimal due to negligible systemic absorption. |
| Fetal Monitoring |
■ FDA Black Box Warning
None.
| Serious Effects |
["Known hypersensitivity to polyethylene glycol or any component of the formulation","Bowel obstruction or perforation","Toxic colitis or megacolon","Gastrointestinal obstruction or ileus"]
| Precautions | ["Use for constipation lasting more than 2 weeks may indicate a serious condition; consider further evaluation.","Do not use if experiencing nausea, vomiting, abdominal pain, or a sudden change in bowel habits lasting more than 2 weeks.","Allergic reactions including urticaria and rash have been reported.","Risk of electrolyte disturbances with prolonged use or in patients with renal impairment."] |
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| No specific maternal or fetal monitoring is required. Standard prenatal care is sufficient. |
| Fertility Effects | No known adverse effects on fertility in animal studies or human reports. Polyethylene glycol 3350 is not systemically absorbed, so reproductive effects are unlikely. |