Access to a special dosage form of a medication is essential when administration to infants and children and selected other populations is required. Some drugs necessary for pediatric patients are not commercially available in dosage forms appropriate for use in this population. These drugs may be prepared extemporaneously for use in individual patients. Physical and chemical properties of drugs and excipients should be considered when preparing extemporaneous formulations. These formulations, however, may lack studies to document stability, bioavailability, pharmacokinetics, pharmacodynamics, efficacy and tolerability.