General Pharmacology Practice Questions

Q: What is the drug of choice for the treatment of malignant hyperthermia?

Dantrolene sodium. **Explanation:** **Malignant Hyperthermia (MH)** is a life-threatening pharmacogenetic disorder triggered by volatile anesthetics (e.g., Halothane) and depolarizing muscle relaxants (e.g., Succinylcholine). It involves a mutation in the **Ryanodine Receptor (RyR1)**, leading to massive calcium release from the sarcoplasmic reticulum, resulting in muscle rigidity, hypermetabolism, and severe hyperthermia. **Why Dantrolene Sodium is the Correct Answer:** Dantrolene is a direct-acting skeletal muscle relaxant. It acts as an antagonist at the **RyR1 receptor**, effectively blocking the release of calcium from the sarcoplasmic reticulum. By restoring calcium homeostasis, it halts the hypermetabolic process, making it the specific life-saving antidote for MH. **Why Other Options are Incorrect:** * **Potassium Chloride:** MH often causes hyperkalemia due to rhabdomyolysis; administering potassium would be dangerous and potentially fatal. * **Atropine:** This is an anticholinergic used to treat bradycardia or organophosphate poisoning. It has no role in calcium signaling in skeletal muscle. * **Corticosteroids:** While used to reduce inflammation or cerebral edema, they do not address the underlying pathophysiology of MH. **High-Yield Clinical Pearls for NEET-PG:** * **Early Sign:** The earliest clinical sign of MH is an **increase in end-tidal CO2 (ETCO2)**, followed by masseter muscle rigidity. * **Safe Agents:** For patients with a history of MH, safe alternatives include IV Propofol, Ketamine, and Ester/Amide local anesthetics. * **Dantrolene Formulation:** Modern formulations like *Ryanodex* require less diluent, allowing for faster administration. * **Other Uses of Dantrolene:** It is also used in the management of Neuroleptic Malignant Syndrome (NMS) and spasticity associated with upper motor neuron lesions.

Q: 6-Mercaptopurine (6-MP), frequently used in drug regimens for neoplastic disease, is metabolized by xanthine oxidase. Major dose reductions are advised in patients who are being treated with which of the following drugs that inhibit xanthine oxidase?

Allopurinol. The correct answer is **Allopurinol**. **Mechanism of Interaction:** 6-Mercaptopurine (6-MP) is a purine analog used in the treatment of leukemia [3]. Its primary metabolic pathway involves oxidation by the enzyme **xanthine oxidase (XO)** into inactive 6-thiouric acid [1]. **Allopurinol** is a potent inhibitor of xanthine oxidase (clinically used for gout) [2]. When administered concurrently, Allopurinol prevents the degradation of 6-MP, leading to toxic systemic levels of the chemotherapy drug [1]. This results in severe, life-threatening bone marrow suppression. Therefore, if a patient requires both drugs, the dose of 6-MP must be reduced to **25–33% (1/3rd to 1/4th)** of the original dose. **Analysis of Incorrect Options:** * **A. Cimetidine:** An H2-receptor antagonist and a known microsomal enzyme (Cytochrome P450) inhibitor, but it does not inhibit xanthine oxidase. * **B. Sulfinpyrazone:** A uricosuric agent that inhibits the reabsorption of uric acid in the proximal tubule; it does not inhibit the synthesis of uric acid via xanthine oxidase . * **D. Indomethacin:** A non-steroidal anti-inflammatory drug (NSAID) used for acute gouty arthritis; it inhibits cyclooxygenase (COX) but has no effect on purine metabolism. **NEET-PG High-Yield Pearls:** * **Azathioprine**, a prodrug of 6-MP, follows the same metabolic rule. Its dose must also be reduced when given with Allopurinol or Febuxostat. * **Febuxostat** is a newer, non-purine selective inhibitor of xanthine oxidase that carries the same interaction risk. * **Thiopurine Methyltransferase (TPMT):** This is the other major enzyme that metabolizes 6-MP. Genetic deficiency of TPMT also leads to 6-MP toxicity. * **Drug of Choice:** Allopurinol is the drug of choice for preventing **Tumor Lysis Syndrome** during chemotherapy [1].

Q: Which of the following statements is NOT true regarding mycophenolate mofetil?

It is nephrotoxic.. **Explanation:** **Mycophenolate Mofetil (MMF)** is a potent immunosuppressant widely used in transplant medicine. The correct answer is **D** because MMF is notably **not nephrotoxic**, which distinguishes it from calcineurin inhibitors (CNIs) like Cyclosporine and Tacrolimus. 1. **Why Option D is the correct answer:** MMF’s primary advantage in renal transplantation is its lack of nephrotoxicity. Its dose-limiting toxicities are primarily **gastrointestinal** (nausea, vomiting, diarrhea) and **hematological** (leukopenia, anemia). Because it does not damage the kidneys, it is often used to allow for a reduction in the dose of nephrotoxic CNIs. 2. **Analysis of Incorrect Options:** * **Option A:** MMF is indeed a **prodrug** that is rapidly hydrolyzed in the liver to its active metabolite, **mycophenolic acid (MPA)**. * **Option B:** In clinical practice, the "Triple Drug Regimen" for maintenance immunosuppression typically consists of a **CNI** (Tacrolimus/Cyclosporine), an **antimetabolite** (MMF), and a **glucocorticoid** (Prednisolone). * **Option C:** MMF and Azathioprine are both antimetabolites that inhibit purine synthesis. Using them together increases the risk of severe bone marrow suppression without added benefit; therefore, they are **not** used concurrently. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Potent, reversible, non-competitive inhibitor of **Inosine Monophosphate Dehydrogenase (IMPDH)**. This inhibits the *de novo* pathway of guanosine nucleotide synthesis. * **Selectivity:** T and B lymphocytes are highly dependent on the *de novo* pathway (unlike other cells which use the salvage pathway), making MMF a selective lymphocyte inhibitor. * **Teratogenicity:** MMF is associated with "Mycophenolate Embryopathy" (ear and facial abnormalities) and is contraindicated in pregnancy.

Q: What is the term for a pharmaceutical agent specifically developed to treat a rare medical condition affecting fewer than 200,000 people?

Orphan Drug. ### Explanation **Correct Option: A. Orphan Drug** An **Orphan Drug** is a pharmaceutical agent intended for the diagnosis, prevention, or treatment of a rare disease. In the United States (under the Orphan Drug Act), a rare disease is defined as one affecting **fewer than 200,000 people**. Because the market for such drugs is small, pharmaceutical companies are often reluctant to develop them due to high costs and low potential for profit. To encourage development, governments provide incentives such as tax credits, simplified marketing authorization, and extended patent exclusivity (usually 7 years). **Analysis of Incorrect Options:** * **B. Primary Drug:** This is not a standard pharmacological classification. It may be confused with "Essential Medicines," which are drugs that satisfy the priority healthcare needs of a population. * **C. Rare Drug:** While these drugs treat rare diseases, "Rare Drug" is not the formal regulatory or pharmacological term used in medical literature or examinations. * **D. Pioneer Drug:** Also known as a "Brand-name" or "Innovator" drug, this refers to the first version of a drug produced by a manufacturer and protected by a patent, regardless of the prevalence of the disease it treats. **High-Yield Clinical Pearls for NEET-PG:** * **Examples of Orphan Drugs:** Digoxin immune Fab (for digitalis toxicity), Fomepizole (for methanol poisoning), Thalidomide (for leprosy/multiple myeloma), and Liothyronine (for myxedema coma). * **Indian Context:** The prevalence threshold for rare diseases in India is generally considered 1 in 5,000 people or less. * **Key Incentive:** The primary hurdle for orphan drugs is the **"lack of commercial viability,"** which is offset by government-granted **market exclusivity**.

Q: Which of the following is NOT a function of Prostaglandin E1?

Induction of puberty. **Explanation:** Prostaglandin E1 (PGE1), also known as **Alprostadil**, is a potent vasodilator and smooth muscle relaxant [1]. The correct answer is **Induction of puberty**, as PGE1 has no physiological or pharmacological role in the onset of puberty, which is governed by the hypothalamic-pituitary-gonadal axis (GnRH, LH, and FSH). **Analysis of Options:** * **Erectile Dysfunction (A):** Alprostadil is used as a second-line treatment for ED [1]. It can be administered via intracavernosal injection or intraurethral suppository to induce vasodilation and relax the trabecular smooth muscle of the corpora cavernosa. * **Patent Ductus Arteriosus (B & D):** These options refer to the clinical management of PDA. PGE1 is used to **maintain patency** of the ductus arteriosus in neonates with cyanotic heart disease (e.g., Transposition of Great Arteries) until surgery can be performed [1], [2]. Conversely, NSAIDs like Indomethacin or Ibuprofen are used to *close* a PDA. (Note: Option D likely refers to the "maintenance" of the PDA). **High-Yield Clinical Pearls for NEET-PG:** * **Misoprostol (PGE1 analog):** Used for NSAID-induced peptic ulcers and medical abortion (combined with Mifepristone) [1]. * **Dinoprostone (PGE2):** Used for cervical ripening and induction of labor [1]. * **Latanoprost (PGF2̑):** First-line treatment for Open-Angle Glaucoma (increases uveoscleral outflow) [1]. * **Epoprostenol (PGI2):** Used in Pulmonary Arterial Hypertension [1]. * **Side Effect:** A common side effect of Alprostadil injection is priapism (prolonged erection).

Q: What specific information is collected during Phase IV clinical trials?

Drug toxicity. **Explanation:** **Phase IV Clinical Trials**, also known as **Post-Marketing Surveillance**, are conducted after a drug has been approved by regulatory authorities (like the FDA or CDSCO) and is available to the general public. **Why "Drug Toxicity" is the correct answer:** The primary objective of Phase IV is to monitor the **long-term safety** and detect **rare or delayed adverse drug reactions (ADRs)** that may not have surfaced during Phase I-III trials. Since pre-approval trials involve a limited number of highly selected patients (usually <3,000), they lack the statistical power to detect rare toxicities (e.g., 1 in 10,000). Phase IV observes the drug’s performance in the "real world" across diverse populations, making it the definitive stage for identifying chronic toxicity and idiosyncratic reactions. **Analysis of Incorrect Options:** * **A. Drug Efficacy:** This is primarily established during **Phase II** (initial efficacy) and **Phase III** (confirmatory efficacy in large groups). * **B. Drug Potency:** This is a pharmacodynamic property usually determined during **pre-clinical animal studies** and **Phase I** trials. * **D. Other possible uses:** While new indications may be discovered incidentally, the *specific regulatory purpose* of Phase IV is safety monitoring. Exploring new uses usually requires starting new Phase II/III trials for that specific indication. **High-Yield NEET-PG Pearls:** * **Phase 0:** Microdosing studies (Human microdosing) to study pharmacokinetics. * **Phase I:** Safety and tolerability in **healthy volunteers** (Exception: Anti-cancer drugs). * **Phase II:** Smallest group of **patients**; determines the therapeutic dose range. * **Phase III:** Large-scale, multicentric, randomized controlled trials (RCTs); the "Gold Standard." * **Black Box Warning:** Often added to a drug's label based on Phase IV toxicity data.

Q: Which of the following inhibits CYP-P450?

Grapefruit juice. **Explanation:** The correct answer is **Grapefruit juice**. **1. Why Grapefruit juice is correct:** Grapefruit juice contains compounds called **furanocoumarins** (e.g., bergamottin), which are potent **inhibitors** of the **CYP3A4** enzyme, primarily in the intestinal wall. By inhibiting this enzyme, grapefruit juice reduces the first-pass metabolism of many drugs, leading to increased plasma concentrations and potential toxicity. Common drugs affected include statins (Atorvastatin), calcium channel blockers (Amlodipine), and immunosuppressants (Cyclosporine). **2. Why the other options are incorrect:** * **Ethanol:** Chronic alcohol consumption is a well-known **enzyme inducer** (specifically CYP2E1). However, acute large doses can act as an inhibitor. In the context of standard pharmacology exams, ethanol is typically categorized as an inducer. * **Rifampicin:** This is one of the most potent **broad-spectrum enzyme inducers**. It increases the synthesis of multiple CYP enzymes (CYP3A4, 2C9, 2C19), leading to decreased efficacy of drugs like oral contraceptives and warfarin. * **Procainamide:** This is a Class 1A antiarrhythmic drug. It is metabolized via **acetylation** (by the NAT2 enzyme), not primarily through the CYP-P450 system, and it does not act as a significant inducer or inhibitor. **3. High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Enzyme Inhibitors (VITAMIN K):** **V**alproate, **I**soniazid, **T**ame (Cimetidine), **A**miodarone, **M**acrolides (except Azithromycin), **I**ndinavir, **N**on-DHP CCBs (Verapamil/Diltiazem), **K**etoconazole (and Grapefruit juice). * **Mnemonic for Enzyme Inducers (GPRS Cell Phone):** **G**riseofulvin, **P**henytoin, **R**ifampicin, **S**moking, **C**arbamazepine, **P**henobarbitone. * **Note:** Erythromycin inhibits CYP enzymes, but **Azithromycin** does not, making it a safer choice to avoid drug interactions.

Question 1

What is the drug of choice for the treatment of malignant hyperthermia?

Accepted Answer

Dantrolene sodium

Answer

Potassium chloride

Answer

Atropine

Answer

Corticosteroids

Question 2

6-Mercaptopurine (6-MP), frequently used in drug regimens for neoplastic disease, is metabolized by xanthine oxidase. Major dose reductions are advised in patients who are being treated with which of the following drugs that inhibit xanthine oxidase?

Accepted Answer

Allopurinol

Answer

Cimetidine

Answer

Sulfinpyrazone

Answer

Indomethacin

Question 3

Which of the following statements is NOT true regarding mycophenolate mofetil?

Accepted Answer

It is nephrotoxic.

Answer

It is a prodrug of mycophenolic acid.

Answer

It can be used concurrently with a calcineurin inhibitor and a glucocorticoid.

Answer

It cannot be used concurrently with azathioprine.

Question 4

What is the term for a pharmaceutical agent specifically developed to treat a rare medical condition affecting fewer than 200,000 people?

Accepted Answer

Orphan Drug

Answer

Primary Drug

Answer

Rare Drug

Answer

Pioneer Drug

Question 5

According to the Food and Drug Administration (FDA) lactation categories, what does category 'S' refer to?

Accepted Answer

Potential for significant effects on nursing infants; medication should be given with caution.

Answer

Safe for nursing infant; medication usually compatible with breastfeeding.

Answer

Safety in nursing infants unknown; inadequate literature available.

Answer

Not safe for nursing infants; medication contraindicated or requires cessation of breastfeeding.

Question 6

Which of the following is NOT a function of Prostaglandin E1?

Accepted Answer

Induction of puberty

Answer

Erectile dysfunction

Answer

Treatment of patent ductus arteriosus

Answer

Patent ductus arteriosus

Question 7

Therapeutic drug monitoring is not indicated for which of the following medications?

Accepted Answer

Propranolol

Answer

Phenytoin

Answer

Piroxicam

Answer

Prazosin

Question 8

What specific information is collected during Phase IV clinical trials?

Accepted Answer

Drug toxicity

Answer

Drug efficacy

Answer

Drug potency

Answer

Other possible uses of the drug

Question 9

Therapeutic drug monitoring is indicated for which of the following drugs, except?

Accepted Answer

Cycloserine

Answer

Warfarin

Answer

Phenytoin

Answer

Gentamicin

Question 10

Which of the following inhibits CYP-P450?

Accepted Answer

Grapefruit juice

Answer

Ethanol

Answer

Rifampicin

Answer

Procainamide

General Pharmacology — MCQs

General Pharmacology — MCQs

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