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1. If medicines are administered orally, there is no need to consider first-pass metabolism?
2. If medicines are administered locally, a higher concentration of the medicine can reach the sites of action?
3. If absorption of a medicine occurs too quickly a high blood level might result causing toxicity?
4. A decrease in gastrointestinal motility will lead to a medicine being absorbed quicker?
5. Enteric coated tablets are designed to disintegrate and release their drug in the stomach?
6. Medicines labelled ‘modified release’ can be safely crushed and administered to patients with swallowing difficulties?
7. Hydrophilic drugs can passively diffuse through cell membranes?
8. Usually, only highly lipid-soluble medicines can cross the blood brain barrier and penetrate into the central nervous system?
9. Other than the liver, metabolism of medicines may take place in sites such as the lungs, plasma and intestinal wall?
10. A pro drug is an inactive medicine which is metabolised to an active medicine?
Question 1: The correct answer is False Medicines administered orally are absorbed through the GI tract into the bloodstream. Blood travels immediately to the liver where some drugs are inactivated the first time they pass through e.g. GTN is given sublingually to avoid first pass.
Question 2: The correct answer is True Local administration of medicines allows high concentrations to get to the site of action e.g. local anaesthetic, inhaled medicines such as salbutamol.
Question 3: The correct answer is True Too rapid absorption of medicines can lead to toxic blood levels.
Question 4: The correct answer is True Reduced gastrointestinal motility slows gut transit time and allows greater contact time with intestinal endothelium for medicines to be absorbed.
Question 5: The correct answer is False Enteric coated tablets are designed to disintegrate in the small intestine and therefore protect the stomach e.g. prednisolone EC.
Question 6: The correct answer is False If modified release tablets are crushed the preparation can become immediate release and cause toxicity.
Question 7: The correct answer is False Lipophilic drugs can passively diffuse more easily through the lipid-based cell membrane.
Question 8: The correct answer is True The Blood-Brain barrier allows lipophilic compounds to pass through but more hydrophilic compounds such as water must pass through special channels.
Question 9: The correct answer is True The bulk of drug metabolism takes place in the liver but metabolism occurs in multiple sites including lungs, plasma and intestinal wall.
Question 10: The correct answer is True Pro drugs are usually pharmacologically inactive substances which are metabolised into a pharmacologically active drug e.g. Terfenadine (a non-sedating antihistamine) is activated to form fexofenadine. Terfenadine was taken off the market due to cardiotoxicity at higher doses but its active form fexofenadine is not associated with this problem.
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