PTCB Pharmacology #3 2 — Questions and Answers
Question 1: What is the first-pass effect?
- Drug degradation by stomach acid before absorption
- Extensive drug metabolism by the liver before systemic circulation after oral administration (Correct answer)
- Filtration of drugs by the kidney upon first exposure
- Binding of drugs to plasma proteins upon first distribution
Correct answer: Extensive drug metabolism by the liver before systemic circulation after oral administration
The first-pass effect (hepatic first-pass metabolism) occurs when orally administered drugs are absorbed from the GI tract and pass through the portal circulation to the liver, where significant metabolism occurs before reaching systemic circulation.
Question 2: Which of the following is an example of a drug with significant first-pass metabolism that may require higher oral doses than parenteral doses?
- Amoxicillin
- Morphine (Correct answer)
- Vancomycin
- Heparin
Correct answer: Morphine
Morphine undergoes significant first-pass hepatic metabolism. The oral:IV ratio is approximately 3:1 — a 10 mg IV morphine dose equals approximately 30 mg oral morphine.
Question 3: Which drug class ends in the "-mab" suffix?
- Small molecule kinase inhibitors
- Fusion proteins
- Monoclonal antibodies (Correct answer)
- Recombinant proteins
Correct answer: Monoclonal antibodies
Monoclonal antibodies end in "-mab" (adalimumab, trastuzumab, pembrolizumab, rituximab). "-nib" indicates small molecule kinase inhibitors; "-cept" indicates fusion proteins.
Question 4: Aminoglycoside antibiotics (e.g., gentamicin) primarily cause which serious adverse effects?
- Hepatotoxicity and photosensitivity
- Nephrotoxicity and ototoxicity (Correct answer)
- Cardiotoxicity and pulmonary toxicity
- Myelosuppression and neurotoxicity
Correct answer: Nephrotoxicity and ototoxicity
Aminoglycosides are associated with nephrotoxicity (acute tubular necrosis) and ototoxicity (cochlear damage causing hearing loss, vestibular damage). Drug levels (trough) and renal function must be monitored.
Question 5: What distinguishes Type 1 diabetes from Type 2 diabetes pharmacologically?
- Type 1 can be controlled with oral agents alone
- Type 1 requires insulin; Type 2 can often be managed initially with oral agents (Correct answer)
- Type 2 always requires insulin from diagnosis
- Both types respond equally to metformin
Correct answer: Type 1 requires insulin; Type 2 can often be managed initially with oral agents
Type 1 diabetes results from autoimmune destruction of beta cells, requiring insulin replacement. Type 2 involves insulin resistance and relative deficiency, often managed initially with oral agents like metformin before insulin is added.
Question 6: Which of the following describes "bioavailability"?
- The rate at which a drug is eliminated from the body
- The fraction of administered drug that reaches systemic circulation unchanged (Correct answer)
- The volume in which a drug distributes
- The percentage of drug bound to plasma proteins
Correct answer: The fraction of administered drug that reaches systemic circulation unchanged
Bioavailability (F) is the fraction of an administered dose that reaches the systemic circulation in an active form. IV drugs have 100% bioavailability; oral drugs are typically less due to incomplete absorption and first-pass metabolism.
PTCB Pharmacology #3 2
What is the first-pass effect?