In water-soluble/miscible bases, which type of drug has good release?

• A. Water-soluble
• B. Lipid-soluble
• C. Lipid-insoluble
• D. Amphiphilic

Answer: (B)

In topical release, how a drug exits the vehicle and moves into the skin depends on how well it partitions between the base and the skin. Water-soluble or water-miscible bases are hydrophilic, so drugs that have an affinity for lipids tend to leave the base and partition into the lipid-rich layers of the skin more readily. Lipid-soluble drugs naturally prefer those lipid environments, so they diffuse into and through the skin more effectively when the vehicle is hydrophilic. Water-soluble drugs, being highly soluble in the vehicle, tend to remain in the base longer and release more slowly because their drive to partition into the skin is weaker. Lipid-insoluble drugs would face greater difficulty crossing into the lipid-rich skin, and amphiphilic drugs can behave unpredictably depending on their balance of solubility in the base versus in the skin.