Your activity: 16 p.v.

Lactulose: Drug information

Lactulose: Drug information
(For additional information see "Lactulose: Patient drug information" and see "Lactulose: Pediatric drug information")

For abbreviations, symbols, and age group definitions used in Lexicomp (show table)
Brand Names: US
  • Constulose;
  • Enulose;
  • Generlac;
  • Kristalose
Pharmacologic Category
  • Ammonium Detoxicant;
  • Laxative, Osmotic
Dosing: Adult

Constipation: Oral: 10 to 20 g (15 to 30 mL or 1 to 2 packets) daily; may increase to 40 g (60 mL or 2 to 4 packets) daily if necessary.

Hepatic encephalopathy, treatment or prevention

Hepatic encephalopathy, treatment or prevention:


Note: May consider as chronic therapy for the prevention of recurrent hepatic encephalopathy with or without other therapies (Ref).

Oral: 20 to 30 g (30 to 45 mL) 2 to 4 times daily; may adjust dose every 1 to 2 days to achieve 2 to 3 soft stools/day (Ref).


Note: Identify and treat precipitating factors. May use as monotherapy for initial treatment or in combination with other therapies when initial monotherapy is unsuccessful. Not recommended for routine treatment of minimal hepatic encephalopathy; may consider on a case-by-case basis in patients with decreased quality of life (Ref).

Oral: Initial: 20 to 30 g (30 to 45 mL) every 1 to 2 hours to induce ~2 soft stools/day, then reduce to 20 to 30 g (30 to 45 mL) 2 to 4 times daily; may adjust dose every 1 to 2 days to achieve 2 to 3 soft stools/day (Ref).

Rectal (alternative route): Retention enema: 200 g (300 mL) in 700 mL NS or water, retain for 30 to 60 minutes; may repeat every 4 to 8 hours based on responsiveness to therapy. Note: Once patient can tolerate oral administration, consider transition to oral formulation (Ref).

Dosing: Kidney Impairment: Adult

The renal dosing recommendations are based upon the best available evidence and clinical expertise. Senior Editorial Team: Bruce Mueller, PharmD, FCCP, FASN, FNKF; Jason A. Roberts, PhD, BPharm (Hons), B App Sc, FSHP, FISAC; Michael Heung, MD, MS.

Altered kidney function: No dosage adjustment necessary for any degree of kidney impairment (systemic absorption limited) (Ref).

Hemodialysis, intermittent (thrice weekly): No supplemental dose or dosage adjustment necessary (systemic absorption limited) (Ref).

Peritoneal dialysis: No dosage adjustment necessary (systemic absorption limited) (Ref).

CRRT: No dosage adjustment necessary (systemic absorption limited) (Ref).

PIRRT (eg, sustained, low-efficiency diafiltration): No dosage adjustment necessary (systemic absorption limited) (Ref).

Dosing: Hepatic Impairment: Adult

There are no dosage adjustments provided in the manufacturer's labeling.

Dosing: Pediatric

(For additional information see "Lactulose: Pediatric drug information")

Note: Doses in pediatric patients may be expressed in volume (mL) or weight (g); use extra caution. Oral solution contains 10 g lactulose per 15 mL; packets contain 10 g or 20 g per packet.


Constipation: Limited data available: Infants, Children, and Adolescents: Oral solution (10 g per 15 mL): Oral: 0.667 to 2 g/kg/day (1 to 3 mL/kg/day) divided once or twice daily; maximum daily dose: 60 g/day (90 mL/day) (Ref).

Constipation, palliative care

Constipation, palliative care: Limited data available: Children and Adolescents: Oral solution (10 g per 15 mL): Oral: 2 to 30 mL every 6 to 24 hours (Johnston 2005); others have suggested 5 to 10 mL every 2 hours until bowel movement (Ref).

Portal systemic encephalopathy, prevention

Portal systemic encephalopathy, prevention (PSE): Oral solution (10 g per 15 mL):

Infants: Oral: 1.7 to 6.7 g/day (2.5 to 10 mL/day) in divided doses; adjust dosage to produce 2 to 3 stools/day.

Children and Adolescents: Oral: 26.7 to 60 g/day (40 to 90 mL/day) in divided doses; adjust dosage to produce 2 to 3 stools/day.

Dosing: Kidney Impairment: Pediatric

There are no dosage adjustments provided in manufacturer's labeling.

Dosing: Hepatic Impairment: Pediatric

There are no dosage adjustments provided in manufacturer's labeling.

Dosing: Older Adult

Refer to adult dosing.

Dosage Forms: US

Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product

Packet, Oral:

Kristalose: 10 g (30 ea); 20 g (30 ea)

Generic: 10 g (15 ea)

Solution, Oral:

Constulose: 10 g/15 mL (237 mL, 946 mL) [unflavored flavor]

Enulose: 10 g/15 mL (473 mL) [unflavored flavor]

Generlac: 10 g/15 mL (473 mL, 1892 mL) [unflavored flavor]

Generic: 10 g/15 mL (15 mL, 30 mL, 237 mL, 473 mL, 480 mL [DSC], 946 mL); 20 g/30 mL (30 mL)

Generic Equivalent Available: US


Administration: Adult

Oral solution: May mix with fruit juice, water or milk.

Crystals for oral solution: Dissolve contents of packet in 120 mL water.

Rectal: Dilute with 700 mL of water or NS; administer as retention enema using a rectal balloon catheter; retain for 30 to 60 minutes. May repeat enema immediately if inadvertently evacuated too promptly. Cleansing enemas containing soapsuds or other alkaline agents should not be used.

Administration: Pediatric


Oral solution: May mix with fruit juice, water, or milk.

Crystals for oral solution: Dissolve contents of packet in 120 mL water.

Use: Labeled Indications

Constipation (Constulose, Kristalose): Treatment of constipation.

Hepatic encephalopathy (Enulose, Generlac): Treatment and prevention of recurrence of hepatic encephalopathy.

Medication Safety Issues
Sound-alike/look-alike issues:

Lactulose may be confused with lactose

Adverse Reactions

The following adverse drug reactions are derived from product labeling unless otherwise specified.

Postmarketing: Gastrointestinal: Abdominal cramps (Passmore 1993), abdominal distention (Barish 2010), abdominal distress, abdominal pain (Barish 2010), anorexia (Passmore 1993), bloating (Hudson 2019), diarrhea (Hudson 2019), eructation, flatulence (Kang 2021), nausea (Kang 2021), vomiting (Barish 2010)


Patients requiring a low galactose diet


Concerns related to adverse effects:

• Electrolyte imbalance: Monitor periodically for electrolyte imbalance when lactulose is used >6 months or in patients predisposed to electrolyte abnormalities (eg, elderly, debilitated patients). Hepatic disease may predispose patients to electrolyte imbalance. Infants receiving lactulose may develop hyponatremia and dehydration.

Disease-related concerns:

• Diabetes: Use with caution in patients with diabetes mellitus; solution contains galactose and lactose.

Other warnings/precautions:

• Electrocautery procedures: During proctoscopy or colonoscopy procedures involving electrocautery, a theoretical risk of reaction between H2 gas accumulation and electrical spark may exist; thorough bowel cleansing with a nonfermentable solution is recommended.

Warnings: Additional Pediatric Considerations

Electrolyte imbalances may occur with chronic use or in patients predisposed to electrolyte imbalances including infants; infants may also develop dehydration with hyponatremia.

Metabolism/Transport Effects

None known.

Drug Interactions

Note: Interacting drugs may not be individually listed below if they are part of a group interaction (eg, individual drugs within “CYP3A4 Inducers [Strong]” are NOT listed). For a complete list of drug interactions by individual drug name and detailed management recommendations, use the Lexicomp drug interactions program by clicking on the “Launch drug interactions program” link above.

Dichlorphenamide: Laxatives may enhance the hypokalemic effect of Dichlorphenamide. Risk C: Monitor therapy

Glutamine: May diminish the therapeutic effect of Lactulose. Specifically, glutamine may diminish the ammonia-lowering effects of lactulose. Risk C: Monitor therapy

Vitamin K Antagonists (eg, warfarin): Lactulose may enhance the anticoagulant effect of Vitamin K Antagonists. Risk C: Monitor therapy

Pregnancy Considerations

Lactulose is poorly absorbed following oral administration. Treatment of constipation in pregnant women is similar to that of nonpregnant patients and medications may be used when diet and lifestyle modifications are not effective. Lactulose may be used when an osmotic laxative is needed (Body 2016; Gomes 2018; Shin 2015).

Breastfeeding Considerations

It is not known if lactulose is present in breast milk; however, lactulose is poorly absorbed following oral administration.

The manufacturer recommends that caution be exercised when administering lactulose to nursing women.

Dietary Considerations

Contraindicated in patients on galactose-restricted diet.

Monitoring Parameters

BP, standing/supine; serum electrolytes; bowel movement frequency; fluid status; serum ammonia.

Mechanism of Action

The bacterial degradation of lactulose resulting in an acidic pH inhibits the diffusion of NH3 into the blood by causing the conversion of NH3 to NH4+; also enhances the diffusion of NH3 from the blood into the gut where conversion to NH4+ occurs; produces an osmotic effect in the colon with resultant distention promoting peristalsis; reduces blood ammonia concentration to reduce the degree of portal systemic encephalopathy



Constipation: Up to 24 to 48 hours to produce a normal bowel movement

Encephalopathy: At least 24 to 48 hours

Absorption: Poor

Metabolism: Via colonic flora to lactic acid and acetic acid; requires colonic flora for drug activation

Excretion: Primarily feces; urine (≤3%)

Pricing: US

Pack (Kristalose Oral)

10 g (per each): $10.47

20 g (per each): $10.85

Pack (Lactulose Oral)

10 g (per each): $59.92

Solution (Lactulose Encephalopathy Oral)

10 g/15 mL (per mL): $0.08

Solution (Lactulose Oral)

10 g/15 mL (per mL): $0.03 - $0.10

Disclaimer: A representative AWP (Average Wholesale Price) price or price range is provided as reference price only. A range is provided when more than one manufacturer's AWP price is available and uses the low and high price reported by the manufacturers to determine the range. The pricing data should be used for benchmarking purposes only, and as such should not be used alone to set or adjudicate any prices for reimbursement or purchasing functions or considered to be an exact price for a single product and/or manufacturer. Medi-Span expressly disclaims all warranties of any kind or nature, whether express or implied, and assumes no liability with respect to accuracy of price or price range data published in its solutions. In no event shall Medi-Span be liable for special, indirect, incidental, or consequential damages arising from use of price or price range data. Pricing data is updated monthly.

Brand Names: International
  • Actilax (AU);
  • Aculax (ZA);
  • Amivalex (HU);
  • Avelac (MY);
  • Avilac (IL);
  • Bifiteral (BE, LU);
  • Comfort (BD);
  • Danilax (HK);
  • Dhactulose (HK, MY, SG);
  • Dia-Colon (IT);
  • Dismam L (PE);
  • Duphalac (AE, AT, AU, BE, BG, BH, CL, CN, CO, CR, CY, CZ, DO, EC, EE, EG, ES, FI, FR, GB, GR, GT, HK, HN, HU, ID, IE, IQ, IR, IT, JO, KR, KW, LB, LK, LT, LU, LV, LY, MT, MY, NI, NL, NO, OM, PA, PE, PH, PK, PL, PT, PY, QA, RO, RU, SA, SE, SG, SK, SV, SY, TH, TR, TW, UA, VN, YE, ZA);
  • Extralac (ID);
  • Ezilax (BH, JO, KW, QA);
  • Farcolac (EG);
  • Farlac (BR);
  • Gatinar (CH);
  • Genlac (AU);
  • Genocolan (AR);
  • Hepalac (TH);
  • Lac-Dol (AU);
  • Lacoly (TW);
  • Lacson (ZA);
  • Lactocur (AU, LU);
  • Lactoflor (DE);
  • Lactu (BD);
  • Lactul (MY, TW);
  • Lactulax (CO, CR, DO, EC, GT, HN, ID, MX, NI, PA, SV, UY);
  • Lactulen (CO);
  • Lactulon (PY);
  • Lactulosa (EC);
  • Lactulose-ratiopharm (LU);
  • Lactumed (MY);
  • Lactus (SG);
  • Lactuverlan (DE);
  • Laevolac (AT, CN, HK, IE, IL, IT, NZ, PT, TH, VN);
  • Lagnos NF Jelly for Oral Administration (JP);
  • Laktuvit (UA);
  • Laxadilac (ID);
  • Laxal (PE);
  • Laxalan (PE);
  • Laxette (ZA);
  • Laxilose (CO);
  • Laxiright (LK);
  • Laxol (LK);
  • Laxolac (EG, ET, LK);
  • Laxolad (QA);
  • Laxose (IE);
  • Levolac (FI, NO);
  • Lidong (CN);
  • Lilac (PH);
  • Lipebin (AE, CY, IQ, IR, JO, KW, LB, LY, OM, PE, SA, SY, YE);
  • Livo Luk (IN);
  • Livoluk (TZ);
  • Losalac (TH);
  • Medilax (DK, IS);
  • Medulac (UA);
  • Moderan (VE);
  • Monilac (JP);
  • Movelax (PH);
  • Nophalac (MY);
  • Normase (IL, MT);
  • Normolax (AE, CY, IQ, IR, JO, KW, LB, LY, OM, SA, SY, YE);
  • Opilax (ID);
  • Portalak (HR, UA);
  • Pralax (ID);
  • Ramlac (BH, LB, QA);
  • Regulact (MX);
  • Rialac (AE, BH, JO, KW, QA);
  • Rilax (PH);
  • Sarex (TH);
  • Sedalac (EG);
  • Soflax (AE, SA);
  • Sorbilac (HK, LK);
  • Tenualax (AR);
  • Ticolax (LK);
  • Tulos (BD);
  • Tulotract (DE);
  • Veelac (BD)

For country code abbreviations (show table)
  1. Agrawal A, Sharma BC, Sharma P, Sarin SK. Secondary prophylaxis of hepatic encephalopathy in cirrhosis: an open-label, randomized controlled trial of lactulose, probiotics, and no therapy. Am J Gastroenterol. 2012;107(7):1043-1050. doi:10.1038/ajg.2012.113 [PubMed 22710579]
  2. Barish CF, Voss B, Kaelin B. Comparison of preference and safety of powder and liquid lactulose in adult patients with chronic constipation. Clin Exp Gastroenterol. 2010;3:153-158. doi:10.2147/CEG.S13568 [PubMed 21694860]
  3. Based on expert opinion.
  4. Body C, Christie JA. Gastrointestinal diseases in pregnancy: nausea, vomiting, hyperemesis gravidarum, gastroesophageal reflux disease, constipation, and diarrhea. Gastroenterol Clin North Am. 2016;45(2):267‐283. doi:10.1016/j.gtc.2016.02.005 [PubMed 27261898]
  5. Constulose (lactulose) [prescribing information]. Morristown, NJ: Actavis Inc; January 2011.
  6. Constulose solution (lactulose) [prescribing information]. Morristown, NJ: Actavis Inc; January 2011.
  7. Enulose (lactulose) [prescribing information]. Morristown, NJ: Actavis Inc; January 2011.
  8. Enulose (lactulose) [prescribing information]. Parsippany, NJ: Actavis Pharma Inc; March 2016.
  9. Enulose solution (lactulose) [prescribing information]. Morristown, NJ: Actavis Inc; January 2011.
  10. Ferenci P. Hepatic encephalopathy in adults: treatment. Post TW, ed. UpToDate. Waltham, MA: UpToDate Inc. Accessed September 2, 2021.
  11. Generlac (lactulose) [prescribing information]. Morton Grove, IL: Morton Grove Pharmaceuticals Inc; January 2014.
  12. Gomes CF, Sousa M, Lourenço I, Martins D, Torres J. Gastrointestinal diseases during pregnancy: what does the gastroenterologist need to know?. Ann Gastroenterol. 2018;31(4):385‐394. doi:10.20524/aog.2018.0264 [PubMed 29991883]
  13. Hudson M, Schuchmann M. Long-term management of hepatic encephalopathy with lactulose and/or rifaximin: a review of the evidence. Eur J Gastroenterol Hepatol. 2019;31(4):434-450. doi:10.1097/MEG.0000000000001311 [PubMed 30444745]
  14. Jarzebicka D, Sieczkowska-Golub J, Kierkus J, et al. PEG 3350 versus lactulose for treatment of functional constipation in children: randomized study. J Pediatr Gastroenterol Nutr. 2019;68(3):318-324. doi:10.1097/MPG.0000000000002192 [PubMed 30383579]
  15. Johnston DL, Hentz TA, Friedman DL. Pediatric palliative care. J Pediatr Pharmacol Ther. 2005;10(4):200-214. [PubMed 23118638]
  16. Kang SJ, Cho YS, Lee TH, et al. Medical management of constipation in elderly patients: systematic review. J Neurogastroenterol Motil. 2021;27(4):495-512. doi:10.5056/jnm20210 [PubMed 34642269]
  17. Kliegman RM and St. Geme J, eds. Nelson Textbook of Pediatrics. 21st ed. Saunders Elsevier; 2020.
  18. Kristalose (lactulose) [prescribing information]. Nashville, TN: Cumberland Pharmaceuticals; September 2018.
  19. Kristalose (lactulose) powder for solution [prescribing information]. Nashville, TN: Cumberland Pharmaceuticals Inc; July 2018.
  20. Lactulose [prescribing information]. Amityville, NY: Hi-Tech Pharmacal Co Inc; July 2016.
  21. Lactulose [prescribing information]. Parsippany, NJ: Actavis Pharma Inc; March 2016.
  22. Lactulose Solution [prescribing information]. Amityville, NY: Hi-Tech Pharmacal Co Inc; March 2013.
  23. Lactulose Solution [prescribing information]. Largo, FL: VistaPharm Inc; May 2010.
  24. Lederle FA, Busch DL, Mattox KM, et al. Cost-Effective Treatment of Constipation in the Elderly: A Randomized Double-Blind Comparison of Sorbitol and Lactulose. Am J Med. 1990;89(5):597-601. [PubMed 2122724]
  25. Passmore AP, Wilson-Davies K, Stoker C, Scott ME. Chronic constipation in long stay elderly patients: a comparison of lactulose and a senna-fibre combination. BMJ. 1993;307(6907):769-771. doi:10.1136/bmj.307.6907.769 [PubMed 8219947]
  26. Prasad S, Dhiman RK, Duseja A, et al. Lactulose improves cognitive functions and health-related quality of life in patients with cirrhosis who have minimal hepatic encephalopathy. Hepatology. 2007;45(3):549-559. [PubMed 17326150]
  27. Refer to manufacturer's labeling.
  28. Rosholm JU, Nybo H, Andersen Ranberg K, et al. Hyponatraemia in very old nonhospitalised people: association with drug use. Drugs Aging. 2002;19(9):685-693. [PubMed 12381237]
  29. Rowan-Legg A; Canadian Paediatric Society, Community Paediatrics Committee. Managing functional constipation in children. Paediatr Child Health. 2011;16(10):661-670. [PubMed 23204909]
  30. Shin GH, Toto EL, Schey R. Pregnancy and postpartum bowel changes: constipation and fecal incontinence. Am J Gastroenterol. 2015;110(4):521‐530. doi:10.1038/ajg.2015.76 [PubMed 25803402]
  31. Tabbers MM, DiLorenzo C, Berger MY, et al; European Society for Pediatric Gastroenterology, Hepatology, and Nutrition; North American Society for Pediatric Gastroenterology. Evaluation and treatment of functional constipation in infants and children: evidence-based recommendations from ESPGHAN and NASPGHAN. J Pediatr Gastroenterol Nutr. 2014;58(2):258-274. [PubMed 24345831]
  32. Uribe M, Campollo O, Vargas F, et al. Acidifying enemas (lactitol and lactose) vs. nonacidifying enemas (tap water) to treat acute portal-systemic encephalopathy: a double-blind, randomized clinical trial. Hepatology. 1987;7(4):639-643. doi:10.1002/hep.1840070404 [PubMed 3301614]
  33. Vilstrup H, Amodio P, Bajaj J, et al. Hepatic encephalopathy in chronic liver disease: 2014 Practice Guideline by the American Association for the Study of Liver Diseases and the European Association for the Study of the Liver. Hepatology. 2014;60(2):715-735. [PubMed 25042402]
Topic 9543 Version 300.0