Lecture 13 - Drug Absorption

Question 1

Reasons for withdrawal of drugs from development (6)

Answer 1

Pharmacokinetics
Lack of efficacy
Animal toxicity
Adverse effects in man
Commercial reasons
Miscellaneous

Question 2

Aspirin is a weak acid with a pKa of 3.5. Will the majority of it be in lipid-soluble or water-soluble form in stomach (with pH of 1)?

Answer 2

Ionised molecules are more water soluble. Question is basically asking is a neutral or uncharged molecule lipid or non-lipid soluble. Therefore, as aspirin is a weak acid in the stomach it is lipid soluble.

Question 3

Which of the following property facilitates drug movement across a membrane?
Ionised; low polarity; lower lipid solubility; molecular weight > 2000; inhibits active transport

Answer 3

Low polarity, not ionised difficult to pass through the membrane, lipid solubility, inhibits active transport it would help with movement across membrane, but some drugs are inhibitory so might transport other drugs.

Question 4

Why is ADME important? (7)

Answer 4

Determines speed of onset of a drug’s effect/duration of action.
Essential for safe/intelligent use of medicine by all Drs.
Designing dosing regimes.
Monitoring treatment compliance.
Substance of abuse monitoring.
Medicine licensing required - pharmacokinetic profile required.
Interaction - How we metabolise the drug/what metabolities (toxic??)