General Pharmacology

General Pharmacology Indian Medical PG Question 1: A patient given digoxin started having side effects like nausea and vomiting. The serum concentration of digoxin was 4 ng/mL. The plasma therapeutic range is 1-2 ng/mL. If the half-life of digoxin is 40 hours, how long should one wait before resuming the treatment?

• A. 120 hours
• B. 140-180 hours
• C. 1 half-life (40 hours)
• D. 80 hours (Correct Answer)

General Pharmacology Explanation: ***80 hours (2 half-lives)***- Current digoxin level is **4 ng/mL**, which is **twice the upper therapeutic limit** (2 ng/mL), causing toxicity with nausea and vomiting [1]- After **1 half-life (40 hours)**: concentration reduces to 2 ng/mL (upper therapeutic limit) [2]- After **2 half-lives (80 hours)**: concentration reduces to 1 ng/mL (mid-therapeutic range) [2]- **Clinical rationale**: While 2 ng/mL is technically within range, waiting for 2 half-lives ensures the level is comfortably in the **middle of the therapeutic window** (1 ng/mL), providing a **safer margin** before resuming treatment in a patient who just experienced toxicity- This conservative approach minimizes risk of recurrent toxicity, especially important given the patient's recent symptoms at 4 ng/mL*1 half-life (40 hours)*- After 1 half-life, digoxin level would be 2 ng/mL, which is at the **upper limit** of the therapeutic range- While technically within the therapeutic range, this leaves **minimal safety margin** in a patient who just experienced toxicity- Starting treatment immediately at this level carries higher risk of recurrent side effects*120 hours (3 half-lives)*- After 3 half-lives, the concentration would be **0.5 ng/mL**, which is **below the therapeutic range** (1-2 ng/mL)- This is overly conservative and would **unnecessarily delay** resumption of essential cardiac medication- Could lead to inadequate control of the underlying condition (heart failure or atrial fibrillation)*140-180 hours (3.5-4.5 half-lives)*- This would reduce digoxin to **0.25-0.35 ng/mL**, well below therapeutic levels- This **excessive delay** is not clinically justified and could worsen the patient's cardiac condition- No standard protocol recommends waiting this long before resuming digoxin therapy

General Pharmacology Indian Medical PG Question 2: Which of the following is a safe drug for a nursing mother?

• A. Chloramphenicol
• B. Lithium
• C. Amphetamines
• D. Digoxin (Correct Answer)

General Pharmacology Explanation: ***Digoxin*** - **Digoxin** is considered generally safe during lactation because it has a **low milk-to-plasma ratio** and is poorly absorbed orally by the infant. - The amount of digoxin transferred into breast milk is minimal and unlikely to cause clinically significant effects in the infant. *Chloramphenicol* - **Chloramphenicol** can cause severe adverse effects in infants, including **bone marrow suppression** and the **gray baby syndrome**, due to its ability to cross into breast milk. - Its use is contraindicated in nursing mothers due to these serious risks. *Lithium* - **Lithium** is excreted into breast milk and can reach therapeutic levels in the infant, potentially causing **lethargy**, **hypotonia**, **cyanosis**, and **cardiovascular adverse effects**. - Monitoring infant serum lithium levels is crucial if used, but it's generally advised against due to safety concerns. *Amphetamines* - **Amphetamines** are secreted into breast milk and can cause **irritability**, **poor feeding**, **sleep disturbances**, and even **seizures** in nursing infants. - Due to the high risk of central nervous system stimulation and other adverse effects, amphetamines are generally considered contraindicated during breastfeeding.

General Pharmacology Indian Medical PG Question 3: Which of the following best demonstrates the variability in drug responsiveness among individuals?

• A. Potency
• B. Quantal Dose Response Curve (Correct Answer)
• C. Efficacy
• D. Graded Dose Response Curve

General Pharmacology Explanation: ***Quantal Dose Response Curve*** - A **quantal dose-response curve** plots the percentage of individuals exhibiting a discrete, all-or-none effect against the log dose of a drug. - This curve directly illustrates the **variability in drug responsiveness** within a population by showing the range of doses required to produce a specific effect in different individuals. *Efficacy* - **Efficacy** refers to the maximum effect a drug can produce, regardless of the dose. - While efficacy is an important pharmacological parameter, it describes the drug's overall therapeutic potential, not the **individual variability** in response. *Potency* - **Potency** is a measure of the amount of drug needed to produce an effect of given intensity. - It relates to the absolute dose required for a particular effect but does not directly demonstrate the **inter-individual differences** in biological response. *Graded Dose Response Curve* - A **graded dose-response curve** depicts the relationship between the dose of a drug and the **magnitude of the effect** in a **single biological unit** (e.g., an individual, a tissue, or a cell). - This curve reflects the relationship between drug concentration and effect intensity, but not the **variability in response among different individuals** in a population.

General Pharmacology Indian Medical PG Question 4: Therapeutic drug monitoring is done for:

• A. Aspirin
• B. Heparin
• C. Phenytoin (Correct Answer)
• D. Metformin

General Pharmacology Explanation: ***Phenytoin*** - **Phenytoin** has a **narrow therapeutic window**, meaning the difference between an effective and a toxic dose is small, necessitating close monitoring. - Its **variable absorption** and **nonlinear pharmacokinetics** (saturable metabolism) make individual dosing adjustments critical to maintain therapeutic levels and avoid toxicity. *Aspirin* - **Aspirin** is generally not monitored via plasma levels for its analgesic or antiplatelet effects, as its therapeutic effects are often observed at doses where plasma monitoring is not practical or necessary. - Its primary therapeutic use as an **antiplatelet agent** is evaluated by clinical outcomes rather than drug concentration. *Heparin* - **Heparin** is monitored using coagulation tests like **aPTT (activated partial thromboplastin time)** or anti-Xa levels to assess its anticoagulant effect, not direct drug concentration. - Therapeutic drug monitoring for heparin focuses on its **pharmacodynamic effects** on the clotting cascade rather than its absolute plasma concentration. *Metformin* - **Metformin** has a relatively **wide therapeutic index** and its efficacy is primarily measured by reductions in blood glucose and HbA1c, not by plasma drug concentrations. - It is excreted largely unchanged by the kidneys, and dose adjustments are typically made based on **renal function** and glycemic control.

General Pharmacology Indian Medical PG Question 5: All the following mediate their action using cAMP as second messenger except:

• A. Glucagon
• B. Dopamine
• C. Corticotropin
• D. Vasopressin (Correct Answer)

General Pharmacology Explanation: ***Vasopressin (ADH)*** - Vasopressin has **dual signaling mechanisms** depending on receptor type: - **V2 receptors** (kidney collecting duct): Use **Gs-protein → cAMP pathway** for water reabsorption via aquaporin-2 insertion - **V1 receptors** (vascular smooth muscle): Use **Gq-protein → IP3/DAG pathway** for vasoconstriction - In the context of this question, vasopressin is considered the exception because it has **significant non-cAMP mediated actions** through V1 receptors, unlike the other hormones listed which **predominantly or exclusively** use cAMP - **Note**: This is a teaching point about receptor subtypes; vasopressin DOES use cAMP at V2 receptors *Glucagon* - **Exclusively uses cAMP pathway** in hepatocytes and adipocytes - Binds to **glucagon receptor** (GPCR) → **Gs-protein** → adenylyl cyclase activation → **increased cAMP** → PKA activation - Promotes glycogenolysis, gluconeogenesis, and lipolysis *Dopamine* - **D1 and D5 receptors** are **Gs-coupled** → **stimulate adenylyl cyclase** → **increase cAMP** - Important for neurotransmission (motor control, reward) and renal vasodilation - D2-family receptors (D2, D3, D4) inhibit cAMP but D1-family predominates in many physiological contexts *Corticotropin (ACTH)* - Binds to **melanocortin-2 receptor (MC2R)** on adrenal cortex - **Gs-protein coupled** → adenylyl cyclase activation → **increased cAMP** → PKA activation - Stimulates steroidogenesis and cortisol secretion - **Exclusively cAMP-dependent mechanism**

General Pharmacology Flashcard 1 of 5

Question: All H1 receptor antagonist act by _____ at the H1 receptor site

Answer: inverse agonism

General Pharmacology Flashcard 2 of 5

Question: _____ inhibitors are used in glaucoma and act by relaxing the trabecular meshwork.

Answer: Rho kinase (ROCK)

General Pharmacology Flashcard 3 of 5

Question: Schedule _____ drugs include bacterial vaccines.

Answer: F

General Pharmacology Flashcard 4 of 5

Question: Schedule _____ drugs should be sold only if the prescription is from a registered medical practitioner (RMP).

Answer: H

General Pharmacology Flashcard 5 of 5

Question: Moxifloxacin is metabolized predominantly by the _____

Answer: liver