Solubility is a fundamental concept in physical pharmaceutics that influences the formulation, efficacy, and bioavailability of drugs.
Understanding the solubility of drugs is crucial for developing effective pharmaceutical products.
Solubility can be expressed in various ways, depending on the context and the required precision:
1) Qualitative Solubility Expressions:
Very Soluble: Less than 1 part solvent needed to dissolve 1 part solute.
Freely Soluble: From 1 to 10 parts solvent.
Soluble: From 10 to 30 parts solvent.
Sparingly Soluble: From 30 to 100 parts solvent.
Slightly Soluble: From 100 to 1,000 parts solvent.
Very Slightly Soluble: From 1,000 to 10,000 parts solvent.
Practically Insoluble (or Insoluble): More than 10,000 parts solvent.
2) Quantitative Solubility Expressions:
Molar Solubility: The number of moles of solute that can dissolve in a liter of solution (mol/L).
Mass/Volume Solubility: The mass of solute that can dissolve in a given volume of solvent (mg/mL).
Percentage: The amount of solute per 100 parts of solution, expressed as a percentage (w/v, w/w, v/v).