Basic Principles of Preformulation Studies
While it is tempting to assume that all drug products are financial blockbusters, approximately 70% never generate sufficient sales to recoup their development costs. Table 1.2 shows the top 20…
Ionisation Constants
Understanding acid and base behaviour is extremely important, not only because of the sheer number of ionisable drug substances but because the solubility of an acidic or basic drug substance…
Salt Selection
Acids and bases can be classified as strong through to extremely weak, based on their pKa (Table 6.3). When strong acids react with strong bases the reaction tends to completion,…
Stability Assessment
Long-term 25 ± 2 °C and 60 ± 5% RH 30 ± 2 °C and 65 ± 5% RH 12 months Intermediate 30 ± 2 °C and 65 ± 5%…
Physical Form I – Crystalline Materials
7.2.2 Crystal growth from solution Crystals may grow from solution but this requires that the initial concentration be supersaturated (i.e. above its solubility). Study question 7.1 Why must the solution…
Solubility
The concentration of drug dissolved at this point is known as the equilibrium solubility (usually the term solubility is used alone) and the solution is saturated. If the drug has…
Physical Form II – Amorphous Materials
What would happen if a metastable form could not form (if, for instance, the rate of cooling is too rapid)? Then the volume and enthalpy would continue to decrease along…
Powder Properties
Factors that contribute to driving forces include gravitation, particle mass, the angle of inclination of the powder and any applied load, while factors that contribute to drag forces include forces…
Particle Properties
The numerical aperture is dependent upon both the lens used and the refractive index (n) of the medium through which the light is transmitted: (10.2) where μ is the angle…
Partition Affinity
where P is the partition coefficient and the subscripts indicate the solvent phase. Note that it would be equally possible to define (3.2) In a physiological environment drug substances partition…
