W3-Solution II

• The text discusses various methods for drug dissolution and absorption, including the Beaker Method, Stirrer Method, Rotating Disk Method, Rotating Basket Method, and Paddle Method.
• The text explains that weak acids are more easily absorbed in the stomach due to the predominance of the unionized form (HA) at low pH, whereas weak bases are not easily absorbed due to the presence of the charged form (BH+).
• The text introduces the pH partition model, which considers the GI membrane as a lipid barrier that only allows the absorption of unionized molecules.
• Weak acids with a pKa of around 3.0 are optimally absorbed in the stomach, while weak bases are best absorbed in regions of higher pH, such as the small intestine.
• The text discusses the importance of the octanol-water partition coefficient (P) in determining a drug's ability to partition between water and cellular membranes.
• The text describes how the drug solubility in a mixed solvent (water and a co-solvent) can be calculated using the equation log S = m x + c, where x is the volume fraction of the co-solvent.
• The text mentions that metal ions can catalyze the oxidation of drugs and that this effect can be prevented by adding chelating agents like disodium edetate.
• The text lists some common antioxidants used in pharmaceuticals, such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and nordihydroguariaretic acid (NDGA).
• The text provides references and further reading for those interested in learning more about the topics discussed in the text.

Test your knowledge on the importance of drug solutions for absorption and action in the body. Understand the process from drug dissolution in the gastrointestinal tract to absorption into the bloodstream.