MIRALAX
Clinical safety rating
cautionComprehensive 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. |
| Molecular Weight | 3350 |
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 | Data limited; generally considered safe based on minimal systemic absorption. No evidence of teratogenicity. |
| 2nd trimester | Generally considered safe; minimal systemic absorption. Use if benefit outweighs risk. |
| 3rd trimester | Generally considered safe; minimal systemic absorption. Use if benefit outweighs risk. |
Clinical note
Comprehensive clinical and safety monograph for MIRALAX (MIRALAX).
| Placental transfer | Negligible due to high molecular weight and minimal oral absorption. |
| Breastfeeding | Minimal systemic absorption after oral administration; not expected to pass into breast milk in clinically significant amounts. Considered compatible with breastfeeding. |
| Lactation Rating | L2 (Safer) |
| 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 | 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. |
■ FDA Black Box Warning
None.
| Serious Effects |
Known hypersensitivity to polyethylene glycolGastrointestinal obstructionPerforationToxic colitisParalytic 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. |
| Food/Dietary | None significant. MiraLAX can be mixed with any food or beverage without affecting absorption or efficacy. However, avoid concurrent use with high-fiber supplements or bulk-forming laxatives to prevent excessive stool volume or gas. |
| Clinical Pearls | MiraLAX (polyethylene glycol 3350) is an osmotic laxative that works by drawing water into the bowel, softening stool and increasing frequency of movements. Onset of action is 24-48 hours. It is not absorbed systemically, making it safe for most patients, including those with renal impairment. Avoid in bowel obstruction or perforation. For chronic constipation, titrate dose gradually to avoid bloating. Can be mixed with any beverage (hot or cold) for improved compliance. |
| Patient Advice | Mix one dose (17g) in 4-8 ounces of liquid (water, juice, coffee, soda) and drink immediately. Do not use with starch-thickened liquids. · Do not exceed 7 days of treatment for acute constipation unless directed by a doctor. · May take 24-48 hours to produce a bowel movement. Do not use if you have abdominal pain, nausea, or vomiting. · Store at room temperature. Do not freeze. · Notify your doctor if you experience rectal bleeding or no bowel movement after 7 days. |
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