Sodium Lactate

Nonproprietary Names

BP: Sodium lactate solution PhEur: Natrii lactatis solutio USP: Sodium lactate solution

Synonyms

E325; 2-hydroxypropanoic acid monosodium salt; Lacolin; lactic acid monosodium salt; lactic acid sodium salt; sodium a-hydroxypropionate.

Chemical Name and CAS Registry Number

Sodium lactate [72-17-3]

Empirical Formula and Molecular Weight

C3H5NaO3 112.06

Structural Formula

The PhEur 2005 and USP 28 describe sodium lactate solution as a mixture of the enantiomers of sodium 2-hydroxypropano- ate in approximately equal proportions.

Functional Category

Antimicrobial preservative; buffering agent; emulsifying agent; flavoring agent; humectant.

Applications in Pharmaceutical Formulation or Technology

Sodium lactate is widely used in cosmetics,(1,2) food products and pharmaceutical applications including parenteral and topical formulations.

Therapeutically, sodium lactate is used in infusions as a component of Ringer-lactate solution; as an alternative for sodium hydrogencarbonate in light acidosis; as a rehydrating agent; and as a carrier for electrolyte concentrates or medicines in perfusion/infusion solutions.

Description

Sodium lactate occurs as a clear, colorless, slightly syrupy liquid. It is odorless, or has a slight odor with a characteristic saline taste. It is hygroscopic.

Pharmacopeial Specifications

See Table I.

Sodium Lactate 685

Table I: Pharmacopeial specifications for sodium lactate.

 

Test PhEur 2005 USP 28    

Characters + —    

Identification + +    

Appearance of solution + —    

pH 6.5–9.0 5.0–9.0    

Reducing sugars and sucrose + +    

Methanol 450 ppm(a) +    

Chlorides 450 ppm 40.05%    

Oxalates and phosphates + +    

Sulfates 4100 ppm +    

Aluminum 40.1 ppm(a) —    

Barium + —    

Iron 410 ppm —    

Heavy metals 410 ppm 40.001%  

Bacterial endotoxins +(b) —

Assay 96.0–104.0% 98.0–102.0%

(a) If intended for use in the manufacture of parenteral dosage forms, hemodialysis, or hemofiltration solutions.

(b) If intended for use in the manufacture of parenteral dosage forms without a further appropriate procedure for the removal of bacterial endotoxins.

Typical Properties

Acidity/alkalinity: pH = 7 for an aqueous solution.

Boiling point: 1128C

Hygroscopicity: very hygroscopic.

Melting point: 178C with decomposition at 1408C. Solubility: miscible with ethanol (95%), and with water. Specific gravity: 1.31—1.34

Stability and Storage Conditions

Sodium lactate should be stored in a well-closed container in a cool, dry, place. Sodium lactate is combustible and decomposes upon heating.

Incompatibilities

See Lactic Acid.

Method of Manufacture

See Lactic Acid.

Safety

Sodium lactate occurs naturally in the body and is involved in physiological processes. It is generally regarded as a relatively nontoxic and nonirritant material when used as an excipient. Low concentrations are well tolerated by skin and eye mucosa, although higher concentrations should be avoided.

LD50 (rat, IP): 2 g/kg(3)

686 Sodium Lactate

Handling Precautions

Observe normal precautions appropriate to the circumstances and quantity of material handled. Sodium lactate may cause eye irritation. When heated to decomposition, sodium lactate emits toxic fumes of Na2O.(3)

Regulatory Status

GRAS listed (not for infant formulas). Included in the FDA Inactive Ingredient Guide (epidural, IM, IV, and SC injections; oral suspensions; topical gels and solutions). Included in nonparenteral medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.

Related Substances

Lactic Acid.

Comments

Generally, the commercially available product is a mixture with water containing 70–80% sodium lactate. The EINECS number for sodium lactate is 200-772-0.

Specific References

Suomela A, Kristoffersson E. Dry skin and moisturizing agents.

Acta Pharm Fenn 1983; 92(2): 67–76.

Middleton JD. Sodium lactate as a moisturizer. Cosmet Toiletries 1978; 93(Mar): 85–86.

Lewis RJ, ed. Sax’s Dangerous Properties of Industrial Materials, 11th edn. New York: Wiley, 2004: 2197–2198.

General References

—

Authors

HJ de Jong.

Date of Revision

17 August 2005.

Sodium Lauryl Sulfate

Nonproprietary Names

BP: Sodium lauryl sulfate JP: Sodium lauryl sulfate

Table I: Uses of sodium lauryl sulfate.

Use Concentration (%)

PhEur: Natrii laurilsulfas USPNF: Sodium lauryl sulfate

Anionic emulsifier, forms self-emulsifying bases with fatty alcohols

0.5–2.5

Detergent in medicated shampoos ≈10

Skin cleanser in topical applications 1

Synonyms

Solubilizer in concentrations greater than critical micelle concentration

>0.0025

Dodecyl sodium sulfate; Elfan 240; sodium dodecyl sulfate; sodium laurilsulfate; sodium monododecyl sulfate; sodium monolauryl sulfate; Texapon K12P.

Chemical Name and CAS Registry Number

Sulfuric acid monododecyl ester sodium salt [151-21-3]

Empirical Formula and Molecular Weight

C12H25NaO4S 288.38

The USPNF 23 describes sodium lauryl sulfate as a mixture of sodium alkyl sulfates consisting chiefly of sodium lauryl sulfate (C12H25NaO4S). The PhEur 2005 states that sodium lauryl sulfate should contain not less than 85% of sodium alkyl sulfates calculated as C12H25NaO4S.

Structural Formula

 

Functional Category

Anionic surfactant; detergent; emulsifying agent; skin pen- etrant; tablet and capsule lubricant; wetting agent.

Applications in Pharmaceutical Formulation or Technology

Sodium lauryl sulfate is an anionic surfactant employed in a wide range of nonparenteral pharmaceutical formulations and cosmetics; see Table I.

It is a detergent and wetting agent effective in both alkaline and acidic conditions. In recent years it has found application in analytical electrophoretic techniques: SDS (sodium dodecyl sulfate) polyacrylamide gel electrophoresis is one of the more widely used techniques for the analysis of proteins;(1) and sodium lauryl sulfate has been used to enhance the selectivity of micellar electrokinetic chromatography (MEKC).(2)

Tablet lubricant 1.0–2.0

Wetting agent in dentrifices 1.0–2.0

SEM: 1

Excipient: Sodium lauryl sulfate Manufacturer: Canadian Alcolac Ltd. Magnification: 120×

 

Description

Sodium lauryl sulfate consists of white or cream to pale yellow- colored crystals, flakes, or powder having a smooth feel, a soapy, bitter taste, and a faint odor of fatty substances.

Pharmacopeial Specifications

See Table II.

Typical Properties

Acidity/alkalinity: pH = 7.0–9.5 (1% w/v aqueous solution)

Acid value: 0

Antimicrobial activity: sodium lauryl sulfate has some bacter- iostatic  action  against  Gram-positive  bacteria  but  is

688 Sodium Lauryl Sulfate

ineffective against many Gram-negative microorganisms. It potentiates the fungicidal activity of certain substances such as sulfanilamide and sulfathiazole.

Critical micelle concentration: 8.2 mmol/L (0.23 g/L) at 208C

Density: 1.07 g/cm3 at 208C

HLB value: ≈40

Interfacial tension: 11.8 mN/m (11.8 dynes/cm) for a 0.05% w/v solution (unspecified nonaqueous liquid) at 308C.

Melting point: 204–2078C (for pure substance)

Moisture content: 45%; sodium lauryl sulfate is not hygro- scopic.

Solubility: freely soluble in water, giving an opalescent solution; practically insoluble in chloroform and ether.

Spreading coefficient: —7.0 (0.05% w/v aqueous solution) at 308C

Surface tension: 25.2 mN/m (25.2 dynes/cm) for a 0.05% w/v aqueous solution at 308C

Wetting time (Draize test): 118 seconds (0.05% w/v aqueous solution) at 308C

SEM: 2

Excipient: Sodium lauryl sulfate Manufacturer: Canadian Alcolac Ltd. Magnification: 600×

 

Table II: Pharmacopeial specifications for sodium lauryl sulfate.

 

Test JP 2001 PhEur 2005 USPNF 23    

Identification + + +    

Alkalinity + + +    

Heavy metals — — 40.002%    

Sodium chloride 48.0% + +    

Sodium sulfate + + +    

Unsulfated alcohols 44.0% — 44.0%    

Nonesterified alcohols — 44.0% —    

Total alcohols 559.0% — 559.0%    

Organic volatile impurities — — +    

Water 45.0% — —    

Assay (as C12H25NaO4S) — 585.0% —  

Stability and Storage Conditions

Sodium lauryl sulfate is stable under normal storage conditions. However, in solution, under extreme conditions, i.e., pH 2.5 or below, it undergoes hydrolysis to lauryl alcohol and sodium bisulfate.

The bulk material should be stored in a well-closed container away from strong oxidizing agents in a cool, dry place.

Incompatibilities

Sodium lauryl sulfate reacts with cationic surfactants, causing loss of activity even in concentrations too low to cause precipitation. Unlike soaps, it is compatible with dilute acids and calcium and magnesium ions.

Solutions of sodium lauryl sulfate (pH 9.5–10.0) are mildly corrosive to mild steel, copper, brass, bronze, and aluminum. Sodium lauryl sulfate is also incompatible with some alkaloidal salts and precipitates with lead and potassium salts.

Method of Manufacture

Sodium lauryl sulfate is prepared by sulfation of lauryl alcohol, followed by neutralization with sodium carbonate.

Safety

Sodium lauryl sulfate is widely used in cosmetics and oral and topical pharmaceutical formulations. It is a moderately toxic material with acute toxic effects including irritation to the skin, eyes, mucous membranes, upper respiratory tract, and sto- mach. Repeated, prolonged exposure to dilute solutions may cause drying and cracking of the skin; contact dermatitis may develop.(3) Prolonged inhalation of sodium lauryl sulfate will damage the lungs. Pulmonary sensitization is possible, resulting in hyperactive airway dysfunction and pulmonary allergy. Animal studies have shown intravenous administration to cause marked toxic effects to the lung, kidney, and liver. Mutagenic testing in bacterial systems has proved negative.(4)

Adverse reactions to sodium lauryl sulfate in cosmetics and pharmaceutical formulations mainly concern reports of irrita- tion to the skin(3,5–7) or eyes(8) following topical application.

Sodium lauryl sulfate should not be used in intravenous preparations for humans. The probable human lethal oral dose is 0.5–5.0 g/kg.

LD50 (mouse, IP): 0.25 g/kg(9) LD50 (mouse, IV): 0.12 g/kg LD50 (rat, oral): 1.29 g/kg LD50 (rat, IP): 0.21 g/kg

LD50 (rat, IV): 0.12 g/kg

Handling Precautions

Observe normal precautions appropriate to the circumstances and quantity of material handled. Inhalation and contact with the skin and eyes should be avoided; eye protection, gloves, and other protective clothing, depending on the circumstances, are recommended. Adequate ventilation should be provided or a dust respirator should be worn. Prolonged or repeated exposure should be avoided. Sodium lauryl sulfate emits toxic fumes on combustion.

Sodium Lauryl Sulfate 689

Regulatory Status

GRAS listed. Included in the FDA Inactive Ingredients Guide (dental preparations; oral capsules, suspensions, and tablets; topical and vaginal preparations). Included in nonparenteral medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.

Related Substances

Cetostearyl alcohol; cetyl alcohol; magnesium lauryl sulfate; wax, anionic emulsifying.

Magnesium lauryl sulfate

Empirical formula: C12H26O4S·HMg

CAS number: [3097-08-3]

Comments: a soluble tablet lubricant.(10) The EINECS number for magnesium lauryl sulfate is 221-450-6.

Comments

A specification for sodium lauryl sulfate is contained in the Food Chemicals Codex (FCC). The EINECS number for sodium lauryl sulfate is 205-788-1.

Specific References

Smith BJ. SDS polyacrylamide gel electrophoresis of proteins.

Methods Mol Biol 1994; 32: 23–34.

Riekkola ML, Wiedmar SK, Valko IE, Siren H. Selectivity in capillary electrophoresis in the presence of micelles, chiral selectors and non-aqueous media. J Chromatogr 1997; 792A: 13–35.

Wigger-Alberti W, Krebs A, Elsner P. Experimental irritant contact dermatitis due to cumulative epicutaneous exposure to sodium lauryl sulphate and toluene: single and concurrent application. Br J Dermatol 2000; 143: 551–556.

Mortelmans K, Haworth S, Lawlor T, et al. Salmonella mutageni- city tests II: results from the testing of 270 chemicals. Environ Mutagen 1986; 8 (Suppl. 7): 1–119.



Blondeel A, Oleffe J, Achten G. Contact allergy in 330 dermatological patients. Contact Dermatitis 1978; 4(5): 270–276.

Bruynzeel DP, van Ketel WG, Scheper RJ, von Blomberg-van der Flier BME. Delayed time course of irritation by sodium lauryl sulfate: observations on threshold reactions. Contact Dermatitis 1982; 8(4): 236–239.

Eubanks SW, Patterson JW. Dermatitis from sodium lauryl sulfate in hydrocortisone cream. Contact Dermatitis 1984; 11(4): 250–

251.

Grant WM. Toxicology of the Eye, 2nd edn. Springfield, IL: Charles C Thomas, 1974: 964.

Lewis RJ, ed. Sax’s Dangerous Properties of Industrial Materials, 11th edn. New York: Wiley, 2004: 3258–3259.

Caldwell HC, Westlake WJ. Magnesium lauryl sulfate–soluble lubricant [letter]. J Pharm Sci 1972; 61: 984–985.

General References

Hadgraft J, Ashton P. The effect of sodium lauryl sulfate on topical drug bioavailability. J Pharm Pharmacol 1985; 37 (Suppl.): 85P.

Nakagaki M, Yokoyama S. Acid-catalyzed hydrolysis of sodium dodecyl sulfate. J Pharm Sci 1985; 74: 1047–1052.

Vold RD, Mittal KL. Determination of sodium dodecyl sulfate in the presence of lauryl alcohol. Anal Chem 1972; 44(4): 849–850.

Wan LSC, Poon PKC. The interfacial activity of sodium lauryl sulfate in the presence of alcohols. Can J Pharm Sci 1970; 5: 104–107.

Wang L-H, Chowhan ZT. Drug–excipient interactions resulting from powder mixing V: role of sodium lauryl sulfate. Int J Pharm 1990; 60: 61–78.

Authors

S Behn.

Date of Revision

15 August 2005.