LACTULOSE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for LACTULOSE (LACTULOSE).
Lactulose is a non-absorbable disaccharide that is metabolized by colonic bacteria to short-chain fatty acids, primarily lactic acid and acetic acid, resulting in an osmotic effect that increases stool water content and softens stools. In hepatic encephalopathy, lactulose acidifies the colonic lumen, converting NH3 to NH4+, which is poorly absorbed, and reduces systemic ammonia levels.
| Metabolism | Lactulose is not metabolized in the human gastrointestinal tract; it is metabolized by colonic bacteria to lactic acid, acetic acid, and other short-chain fatty acids. |
| Excretion | Primarily fecal (unaltered, >90%). Minimal renal excretion (<5% as metabolites). Very small amount (approximately 3%) excreted in urine as unchanged drug. |
| Half-life | 1-2 hours (terminal elimination half-life for lactulose). However, its clinical effect is not dependent on systemic half-life; the drug acts locally in the colon. |
| Protein binding | Negligible (<1%). Does not bind significantly to plasma proteins. |
| Volume of Distribution | Approximately 0.4 L/kg. Confined to extracellular fluid; minimal tissue distribution due to poor systemic absorption. |
| Bioavailability | Oral: <2% due to minimal absorption. Rectal (enema): <2%, essentially no systemic absorption. Systemic bioavailability is negligible. |
| Onset of Action | For laxative effect: 24-48 hours after oral administration. For hyperammonemia reduction: 2-4 hours after oral administration (enema: 30-60 minutes). |
| Duration of Action | Laxative effect: variable, typically 24-48 hours after single dose; sustained effect with repeated dosing. For hyperammonemia: duration depends on continued dosing; effects persist as long as drug reaches colon. |
Constipation: 15-30 mL (10-20 g) orally once daily, increased to 45-60 mL (30-40 g) daily if needed. Hepatic encephalopathy: 30-45 mL (20-30 g) orally 3-4 times daily; titrate to produce 2-3 soft stools daily.
| Dosage form | SOLUTION |
| Renal impairment | No dose adjustment required for renal impairment. |
| Liver impairment | No specific Child-Pugh based adjustments; use with caution in severe hepatic impairment due to risk of electrolyte disturbances. |
| Pediatric use | Infants: 2.5-10 mL/day in divided doses. Children 1-5 years: 5-10 mL/day. Children 6-12 years: 10-15 mL/day. Adolescents: 15-30 mL/day. All doses orally once daily, adjust to produce soft stools. |
| Geriatric use | Initiate at low end of adult dosing (15 mL/day); monitor for electrolyte imbalance and dehydration due to age-related comorbidities and polypharmacy. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for LACTULOSE (LACTULOSE).
| Breastfeeding | Lactulose is excreted into breast milk in very small amounts due to its low systemic absorption after oral administration. The M/P (milk-to-plasma) ratio has not been specifically determined, but it is expected to be low. Adverse effects in nursing infants are unlikely. Lactulose is considered compatible with breastfeeding by the American Academy of Pediatrics. |
| Teratogenic Risk | Lactulose is classified as FDA Pregnancy Category B. Animal studies have not demonstrated fetal risk, and there are no adequate and well-controlled studies in pregnant women. Based on available data, lactulose is not associated with a significant risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes. Due to its minimal systemic absorption, the risk of teratogenicity is considered low across all trimesters. |
■ FDA Black Box Warning
None
| Common Effects | Application site reactions burning irritation itching and redness |
| Serious Effects |
Hypersensitivity to lactulose or any component of the formulation; patients on a galactose-free diet (contains galactose); gastrointestinal obstruction.
| Precautions | ["May cause severe diarrhea leading to electrolyte disturbances, hypokalemia, and hypernatremia","Use with caution in patients with galactose intolerance, lactase deficiency, or glucose-galactose malabsorption","Prolonged use may lead to dependence or need for dose escalation","Monitor for symptoms of excessive flatulence and abdominal distension"] |
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| Fetal Monitoring | No specific maternal or fetal monitoring is required beyond routine prenatal care. Monitor for gastrointestinal effects such as bloating, flatulence, and abdominal discomfort. In patients receiving prolonged high doses, monitor serum electrolytes for potential hypernatremia. No fetal monitoring is indicated. |
| Fertility Effects | There are no known adverse effects of lactulose on fertility based on animal studies and clinical use. Lactulose does not affect reproductive hormone levels or gametogenesis. It is considered safe for use in patients attempting conception. |