Lactose monohydrate

• BPLactose Monohydrate
• JPLactose Hydrate
• Ph. Eur.Lactose Monohydrate
• USP–NFLactose Monohydrate

CapsuLac; GranuLac; Lactochem; lactosum monohydricum; milk sugar; Pharmatose; PrismaLac; SacheLac; SorboLac; SpheroLac; Tablettose

O-β-D-Galactopyranosyl-(1→4)-α-D-glucopyranose monohydrate · [64044-51-5]

UNII EWQ57Q8I5X · PubChem CID 104938

C12H22O11·H2O · 360.31

Diluent (filler)

Typical concentrations: q.s. · Dosage forms: Solid

Widely used as a filler and diluent in tablets and capsules and, to a lesser extent, in lyophilised products and infant formulas. Fine (milled) grades are used in wet granulation and to make dilutions of potent drugs; coarse sieved grades flow better and are used in capsule filling; specially prepared grades are used as carriers in dry powder inhalers. Spray-dried and anhydrous lactose are preferred for direct compression.

White to off-white crystalline particles or powder. Odourless and slightly sweet-tasting; its sweetness is roughly a fifth of that of sucrose.

Melting point

201–202 °C (dehydrated α-lactose)

Water content

4.5–5.5% w/w (water of crystallisation, by Karl Fischer)

True density

≈ 1.545 g/cm³

Specific rotation

+54.4° to +55.9° (anhydrous basis, at equilibrium)

Solubility

freely soluble in water (about 1 in 5 at 25 °C); practically insoluble in chloroform, ethanol and ether

Mould growth can occur under humid conditions (80% RH and above). Lactose may brown on storage, faster in warm, damp conditions. Solutions show mutarotation. Store in a well-closed container in a cool, dry place.

As a reducing sugar it undergoes Maillard-type condensation with compounds having a primary amine group (for example amino acids, amphetamines and aminophylline), giving brown products; the reaction is faster with amorphous than with crystalline lactose. It is also incompatible with strong oxidisers.

Obtained from whey, the by-product of cheese making. α-Lactose monohydrate crystallises from a supersaturated solution below 93.5 °C; the crystals are separated, dried, milled and sieved into grades of different particle size.

Widely used and generally non-toxic. People with lactase deficiency (lactose intolerance) can develop abdominal cramps, diarrhoea and flatulence after large amounts; the quantities in most tablets and capsules are usually too small to cause symptoms, but this should be considered for sensitive patients.

Observe normal precautions for the quantity handled. Excessive dust should be avoided; eye protection and gloves are recommended.

GRAS listed. Included in the FDA Inactive Ingredient Database (inhalation; oral capsules and tablets; parenteral preparations) and in parenteral and non-parenteral medicines licensed in Europe.

Lactose, anhydrous; lactose, inhalation; lactose, spray-dried; lactose monohydrate and microcrystalline cellulose; lactose monohydrate and povidone.

Lactose monohydrate is not suited to direct compression on its own because of poor flow and compressibility; use spray-dried or agglomerated grades for that. For dry powder inhalers the particle size distribution and fine-particle fraction of the carrier strongly affect drug delivery and must be controlled.