Question

What is pKa and how does it relate to drugs?

Question # 4: What is the blood brain barrier and how does it help to protect us from foreign substances?

Question # 5: What iis the difference between passive and active diffusion of drugs across the blood brain barrier?

Question # 6: What is the difference between Phase I and Phase II biotransformation?

Question # 7: What is first pass metabolism and how does it compare to an active metabolite?

Question # 8: Explain the concept of a half-life?

Question # 9: What is the difference between first-order kinetics and zero-order kinetics?

Question # 10: Explain the concept of a steady state and compare how this would work for someone receiving a beneficial medication vs. someone abusing a street drug?

Answer 1

pKa stands for Protein Kinase A, which is a property of a compound that tells us how acidic it is. The pKa of a drug is the hydrogen ion concentration at which 50% of the drug exists in its ionized hydrophilic form.

4) Blood brain barrier is a semipermeable membrane separating the blood from the cerebrospinal fluid, and constituting a barrier to the passage of cells, particles and large molecules. It helps us from foreign substances as it protects the brain from circulating pathogens. Therefore, blood borne infections are rare.

5) Passive transport is a movement of ions and other atomic or molecular substances across cell membranes without need of energy input. In active diffusion, the solute can move uphill from regions of lower to higher concentration. Active diffusion requires chemical energy unlike passive diffusion. Drugs diffuse across a cell membrane from a region of high concentration to one of low concentration.

6) Phase I biotransformation reactions introduce functional groups on drug with the goal of increasing the polarity of the compound. Oxidation is the most common phase I reaction. Whereas, Phase II biotransformation reactions generally serve as a detoxifying step in drug metabolism. Reducing this, could lead to toxic effects of clinically used drugs. Phase II is also known as conjugation reactions.