CONSTILAC
Clinical safety rating: caution
Comprehensive clinical and safety monograph for CONSTILAC (CONSTILAC).
Constilac (lactulose) is a synthetic disaccharide that is not absorbed in the small intestine. In the colon, it is metabolized by bacteria to short-chain fatty acids (e.g., lactic acid), which osmotically draw water into the bowel, producing a laxative effect. Additionally, in hepatic encephalopathy, the acidification of colonic contents traps ammonia (NH3) as ammonium (NH4+), reducing its absorption.
| Metabolism | Lactulose is not absorbed in the small intestine. It undergoes bacterial metabolism in the colon to lactic acid, acetic acid, and other short-chain fatty acids. |
| Excretion | Primarily fecal as unchanged drug (systemic absorption negligible). Renal excretion accounts for <2% of any absorbed fraction. Biliary excretion is minimal. |
| Half-life | Not applicable due to negligible systemic absorption; lactulose acts locally in the colon. |
| Protein binding | Negligible (<1%) due to minimal systemic absorption. |
| Volume of Distribution | Not applicable (negligible systemic distribution). |
| Bioavailability | Oral: <2% (largely unabsorbed; metabolized by colonic bacteria). |
| Onset of Action | Oral: 24-48 hours for laxative effect; for hepatic encephalopathy, effect may require 2-3 days. |
| Duration of Action | Laxative effect persists for 24-48 hours after cessation; for hepatic encephalopathy, continuous dosing is required. |
Oral, 15-45 mL (10-20 g lactulose) once daily, titrated to produce 2-3 soft stools daily; may be given as a single dose or divided twice daily. Onset of action 24-48 hours.
| Dosage form | SOLUTION |
| Renal impairment | No dose adjustment required for renal impairment. Lactulose is minimally absorbed and renally excreted unchanged; safety established in all stages of chronic kidney disease. |
| Liver impairment | Contraindicated in Child-Pugh class C cirrhosis due to risk of hepatic encephalopathy exacerbation from colonic acidification. In Child-Pugh A and B, standard dosing may be used with caution; monitor for electrolyte disturbances and volume status. |
| Pediatric use | Infants: 2.5-10 mL/day in divided doses. Children 1-5 years: 5-15 mL/day. Children 6-12 years: 15-30 mL/day. Adolescents: 15-45 mL/day. Administer orally; adjust to produce soft stools. |
| Geriatric use | Initiate at lower end of adult dose (15 mL once daily) and titrate slowly to avoid diarrhea and electrolyte imbalances. Monitor for dehydration, hypokalemia, and hypernatremia, especially in patients with renal impairment or on diuretics. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for CONSTILAC (CONSTILAC).
| Breastfeeding | Considered safe during breastfeeding. M/P ratio not applicable as lactulose is not absorbed; no significant excretion into breast milk expected. |
| Teratogenic Risk | No known teratogenic effects. Lactulose is not absorbed systemically; no fetal risk expected in any trimester. |
| Fetal Monitoring | Monitor maternal bowel function and electrolyte balance if prolonged use. No fetal monitoring required. |
■ FDA Black Box Warning
None
| Serious Effects |
["Patients with galactosemia","Intestinal obstruction or suspected obstruction","Undiagnosed abdominal pain"]
| Precautions | ["Use with caution in patients with diabetes mellitus (lactulose may contain small amounts of galactose and lactose)","Electrolyte disturbances (particularly hypokalemia and hypernatremia) may occur with prolonged use","Risk of galactosemia in patients with galactose intolerance","May cause abdominal discomfort, flatulence, and diarrhea"] |
Loading safety data…
| Fertility Effects | No known effects on fertility. |