| Table 4 Characteristics of Lactose Diluents |
| Lactose, Monohydrate (Hydrous) |
| Not directly compressible and therefore used in wet granulation formulations |
| Produces a hard tablet |
| Tablet hardness tends to increase on storage |
| Disintegration time is not affected by tablet hardness |
| Soluble, but a disintegrant is needed |
| Drug release usually not affected by this material |
| Unreactive, except for discoloration when formulated with amines and alkaline materials |
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Contains approximately 5% moisture, and therefore is a potential source of instability with moisture-sensitive drugs |
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| Poor flowability |
| Inexpensive |
| Lactose, Anhydrous |
| Directly compressible |
| Drug release from lactose-matrix tablets is not affected by this material |
| Not free flowing |
| Can pick up moisture at elevated humidities causing a change in tablet dimension |
| Unreactive, except for discoloration when formulated with amines and alkaline material |
| Inexpensive |
| Lactose, Spray-Dried |
| Directly compressible |
| Requires high compression pressures to produce hard tablets |
| Compressibility affected if allowed to dry below 3% moisture |
| Has high dilution capacity |
| Free flowing |
| Drug release from lactose-matrix tablets is not affected by this material |
| Disintegrant is needed |
| Requires a lubricant, but lubricants do not affect binding |
| May discolor in presence of amines, and excess moisture |
| Inexpensive |