GENERLAC
Clinical safety rating: caution
Comprehensive clinical and safety monograph for GENERLAC (GENERLAC).
Lactulose is a synthetic disaccharide that is not absorbed in the small intestine. It is metabolized by colonic bacteria to short-chain fatty acids (e.g., lactic, acetic, and formic acids), which osmotically increase intraluminal water content, soften stool, and stimulate peristalsis. In hepatic encephalopathy, the acidic environment reduces intestinal ammonia production and absorption by promoting conversion of NH3 to NH4+.
| Metabolism | Lactulose is not absorbed systemically; it is metabolized by colonic bacteria to organic acids (lactic, acetic, formic). |
| Excretion | Primarily fecal (≥90%) as unchanged drug via colonic excretion; renal elimination is negligible (<1%). |
| Half-life | Not applicable; lactulose is a non-absorbable disaccharide that exerts a local osmotic effect in the colon without systemic absorption. Systemic half-life is not relevant as it does not enter circulation. |
| Protein binding | Not applicable; lactulose is not absorbed systemically and does not bind to plasma proteins. |
| Volume of Distribution | Not applicable; lactulose remains within the gastrointestinal lumen and is not distributed into body tissues. |
| Bioavailability | Oral: <1% (negligible systemic absorption due to lack of intestinal disaccharidases for hydrolysis). |
| Onset of Action | Oral: 24–48 hours for laxative effect (due to colonic transit and bacterial metabolism); for hepatic encephalopathy, onset of clinical improvement is 24–72 hours. |
| Duration of Action | Laxative effect lasts 24–48 hours after oral administration; for hepatic encephalopathy, duration is dependent on continued dosing; effects on stool pH and ammonia reduction persist with regular use. |
10-45 mL orally once daily, adjusted to produce 2-3 soft stools per day. Maximum 60 mL/day.
| Dosage form | SOLUTION |
| Renal impairment | No dosage adjustment required for any degree of renal impairment, including end-stage renal disease. |
| Liver impairment | No dosage adjustment required for mild to moderate hepatic impairment (Child-Pugh A and B). Use with caution in severe hepatic impairment (Child-Pugh C) due to risk of electrolyte disturbances; monitor serum potassium and consider dose reduction. |
| Pediatric use | Neonates and infants: 2.5-10 mL/day orally in divided doses. Children 1-5 years: 5-15 mL/day. Children 6-12 years: 15-30 mL/day. Adolescents: 15-45 mL/day. All doses adjusted to achieve 2-3 soft stools daily. |
| Geriatric use | Initiate at lower end of dosing range (10-15 mL/day) due to increased risk of electrolyte imbalance and dehydration. Monitor fluid and electrolyte status regularly. No specific dose adjustment required based on age alone. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for GENERLAC (GENERLAC).
| Breastfeeding | Lactulose is not absorbed systemically and does not enter breast milk in significant amounts. M/P ratio not applicable due to lack of systemic absorption. Considered compatible with breastfeeding. |
| Teratogenic Risk | GENERLAC (lactulose) is not systemically absorbed; negligible fetal exposure. No teratogenic effects reported in animal studies or human case series. Considered low risk in all trimesters. |
| Fetal Monitoring |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
["Galactosemia (due to galactose content)","Patients requiring low-galactose diet","Bowel obstruction (oral or rectal use)","Severe dehydration or electrolyte depletion"]
| Precautions | ["May cause severe diarrhea leading to electrolyte imbalance, especially hypokalemia and hypernatremia.","Use with caution in patients with galactosemia (contains galactose and lactose traces).","Risk of intestinal obstruction or perforation if administered via rectal route in patients with bowel obstruction."] |
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| No specific fetal monitoring required. Monitor maternal electrolytes and hydration status if prolonged therapy is needed, especially if diarrhea occurs. |
| Fertility Effects | No known effects on fertility. Lactulose has no systemic hormonal or direct reproductive organ effects. |