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Sodium citrate/sodium lauryl sulfoacetate/glycerol

Sodium citrate/sodium lauryl sulfoacetate/glycerol
Combination of
Sodium citrateLaxative
Sodium lauryl sulfoacetateLaxative
Clinical data
Trade namesMicrolax, Micolette Micro enema
AHFS/Drugs.comInternational Drug Names
ATC code
  • none

Sodium citrate/sodium lauryl sulfoacetate/glycerol sold under the brandname Microlax and Micolette Micro enema, among others, is a small tube of liquid gel that is used to treat constipation.[1]

The main active ingredients are sodium lauryl sulfoacetate (0.90% w/v), sodium citrate (9.0% w/v) and glycerol.[2]

Medical uses

The main use is for treatment of constipation. In surgery it is used for pre-operative evacuation of the bowel.[3] In diagnostic testing it is used before x-ray examinations or physical examinations of the colon.

It has no age limits in regards to children and can be used safely.[4] If used in children under 3 years it is recommended that the nozzle is only inserted half way.[5] It is suggested as a laxative during postnatal period[6] and it is compatible with breastfeeding[7]


Microlax (like any other saline laxative) should not be used in cases of intestinal inflammation.[8]

Mechanism of action

Sodium citrate saline is one of the most effective osmotic laxatives (secondary in action only to magnesium citrate).[8] Its laxative action is the result of osmotic imbalance that extracts bound water from stool and pulls it back into the large bowel. The increased water content softens the stool and stimulates the bowel to contract (move its contents to the rectum).

Sodium lauryl sulfoacetate improves the wetting and penetrating abilities of the solution, sorbitol enhances the water-releasing effect of sodium citrate and glycerol helps to lubricate the stool. The combined action helps to soften hard stools and relieve constipation without straining in a very short period of time ~ 15 min.[9]

The ingredients are not absorbed, distributed or metabolised by the human body, all of the composition is being excreted in faeces.[9]


1960 - Microlax micro-enema was invented in Sweden by Paul Gunnar Embring from Uppsala and Per Ove Mattsson from Stockholm for Pharmacia company.[10] The original purpose of the invention was for clearing the colon and rectum for X-ray investigation "without any risk of the fluid balance of the body being disturbed".[10]

The first use of "Microlax" in commerce was registered in June 16, 1960.[11] In 1962, Microlax registered as the US trademark in February 20, 1962.[11]

In May 1963 first medical article on Microlax published in Danish medical journal Ugeskrift for Læger (Weekly Journal for Physicians).[12]

In 1964, Microenema containing sodium citrate, sodium laurylsulphoacetate and sorbitol was tested in preparation of the bowel for sigmoidoscopy. Results were published in the American Journal of Proctology.[13] In 1965 a comparative study of Microlax and enema published in Ugeskrift for Læger.[14] In 1967 - an article, published in The Medical Journal of Australia proved the results of 1964 US study and confirmed the efficiency of using Microlax as part of preparation for sigmoidoscopy.[15] In 1996 a study in the Journal of the Royal Society of Medicine suggestedmailing "Microlax" micro-enemas to patients who are scheduled for sigmoidoscopy.[16]


  1. ^ Burke A. (1994). "The management of constipation in end-stage disease". Australian Family Physician. Royal Australian College of General Practitioners. 23 (7): 1248–53. PMID 8060271.
  2. ^ "Summary of Product Characteristics PL 36301/0019: Micralax Micro-enema". Medicines and Healthcare Products Regulatory Agency. 2010-05-25. Archived from the original (PDF) on 2014-10-26. Retrieved 2014-10-26.
  3. ^ Mann, Charles V., ed. (2002). "Day Case Haemorrhoidectomy". Surgical Treatment of Haemorrhoids. Springer Science & Business Media. p. 167. ISBN 1852334967. Retrieved 2014-10-26. (Accessed at Google Books)
  4. ^ Thomson, Kate; Tey, Tey; Marks, Michael (2011). Paediatric Handbook, 8th ed. John Wiley & Sons. ISBN 1444359150. Retrieved 2014-10-26. (Accessed at Google Books)
  5. ^ Rutter, Paul; Newby, David (2011). "Osmotic laxatives". Community Pharmacy: Symptoms, Diagnosis and Treatment. Elsevier Health Sciences. p. 280. ISBN 0729580792. Retrieved 2014-10-27. (Accessed at Google Books)
  6. ^ "Women and Newborn Health Service Clinical Guidelines". King Edward Memorial Hospital for Women. September 2014. Archived from the original (PDF) on 2014-10-26. Retrieved 2014-10-26.
  7. ^ Jones, Wendy (2013). "The safety of drugs in breastmilk". Breastfeeding and Medication. Routledge. p. 128. ISBN 1136178155. Retrieved 2014-10-26. (Accessed at Google Books)
  8. ^ a b Capasso, Francesco Capasso; Gaginella, Timothy S. (1997). "Natural Laxatives of Mineral Origin". Laxatives. Springer Science & Business Media. p. 59. ISBN 8847022274. Retrieved 2014-10-27. (Accessed at Google Books)
  9. ^ a b "Microlax Rectal Solution: Summary of Product Characteristics, CRN 2100068". Health Products Regulatory Authority (HPRA), Ireland. 2011-05-30. Archived from the original (PDF) on 2014-11-08. Retrieved 2014-11-08.
  10. ^ a b "US patent: 3211614 (A) ― 1965-10-12". Espacenet. Archived from the original on 2014-10-26. Retrieved 2014-10-26.
  11. ^ a b "Word mark: Microlax". United States Patent and Trademark Office. Archived from the original on 2014-10-26. Retrieved 2014-10-26.
  12. ^ C.J. Ingomar (1963). "Microlax, a new drug for evacuation of the rectum". Ugeskrift for Læger. 125: 736–8. PMID 13956524. Archived from the original on 2014-10-26. Retrieved 2014-10-26.
  13. ^ W. Lieberman (1964). "Rapid patient preparation for sigmoidoscopy by microenema". American Journal of Proctology. 15: 138–41. PMID 14139893.
  14. ^ J. Reimers; M. Knoth (1965). "Preparation for recto-sigmoidoscopy. A comparative study of Microlax and enemata". Ugeskrift for Læger. 127 (35): 1082–4. PMID 5829676.
  15. ^ Hughes L.E. (1967). "The use of a micro-enema as preparation for sigmoidoscopy". The Medical Journal of Australia. 2 (5): 215–7. PMID 6057897.
  16. ^ Marsh SK, Huddy SP (1996). "Self-administered disposable micro-enemas before outpatient sigmoidoscopy". Journal of the Royal Society of Medicine. 89 (11): 616–7. PMC 1295996. PMID 9135589.