Drug dissolution
The kinetic process by which a solid solute enters a solvent to form a homogeneous solution. In pharmacokinetics, the dissolution rate is frequently the rate-limiting step for the systemic absorption of orally administered medications.
Key Determinants
- Solubility: The equilibrium concentration of a solute in a solvent; highly dependent on temperature and pressure.
- Polymorphism: The existence of a substance in multiple crystalline forms. Different polymorphs possess distinct lattice energies, which directly impact solubility and dissolution kinetics.
- Surface Area: The availability of the solid-liquid interface; often manipulated via micronization to increase dissolution speed.
- Environmental Factors: Solvent pH, viscosity, and the pKa of the drug molecule.
Clinical and Industrial Implications
- Bioavailability: Inadequate dissolution can lead to insufficient plasma concentrations, rendering a drug therapeutically ineffective.
- Stability and Quality Control: Unexpected phase transitions can compromise drug manufacturing and safety.
- Case Study: Ritonavir Polymorph Crisis: Unraveling the Mystery of a Failing HIV Drug
- Highlights the catastrophic impact of spontaneous polymorphism shifts in a critical medication.
- Details how a sudden emergence of a less soluble polymorph in Ritonavir led to widespread failure in quality control and threatened the efficacy of a vital HIV treatment.