General Pharmacology Practice Questions

Q: Which of the following is a prodrug?

Levodopa. **Explanation:** A **prodrug** is a pharmacologically inactive compound that must undergo chemical or enzymatic biotransformation within the body to be converted into its active form. **Why Levodopa is the correct answer:** Levodopa is the classic example of a prodrug used in Parkinsonism. It is an amino acid precursor that crosses the blood-brain barrier (BBB) via large neutral amino acid transporters. Once inside the CNS, it undergoes **decarboxylation** by the enzyme *L-amino acid decarboxylase* to become **Dopamine**, which is the active moiety. Dopamine itself cannot be administered directly because it is polar and cannot cross the BBB. **Analysis of Incorrect Options:** * **Amitriptyline:** It is an active Tricyclic Antidepressant (TCA). While it is metabolized into another active metabolite (Nortriptyline), the parent drug itself possesses pharmacological activity. * **Primidone:** It is an anticonvulsant that is metabolized into Phenobarbital and Phenylethylmalonamide (PEMA). However, Primidone itself has independent anticonvulsant activity and is not strictly a prodrug. * **Digitoxin:** This is an active cardiac glycoside. Unlike its counterpart Digoxin, it undergoes extensive hepatic metabolism, but it is active upon administration. **NEET-PG High-Yield Pearls:** * **Common Prodrugs (Mnemonic: "All Prefer Drugs In Car"):** **A**CE inhibitors (except Captopril/Lisinopril), **P**rednisone, **D**ipivefrin, **I**rinotecan, **C**yclophosphamide/Clopidogrel. * **Enalapril** is a prodrug; its active form is **Enalaprilat**. * **Terfenadine** is a prodrug; its active form is **Fexofenadine**. * Prodrugs are often designed to improve bioavailability, reduce first-pass metabolism, or facilitate site-specific delivery (like Levodopa to the brain).

Q: Which of the following is an immunostimulant?

Levamisole. **Explanation:** **Levamisole** is the correct answer. Originally developed as an anthelmintic (anti-worm) medication, it was discovered to have potent **immunomodulatory** properties. It acts as an **immunostimulant** by restoring depressed T-cell and macrophage functions. It enhances phagocytosis, T-cell proliferation, and chemotaxis. * **Clinical Use:** Historically, it was used as an adjuvant in colorectal cancer (with 5-Fluorouracil) and in certain autoimmune conditions. In modern practice, it is occasionally used in pediatric nephrotic syndrome (frequent relapsers) to maintain remission. **Analysis of Incorrect Options:** * **A. Methimazole:** This is an **antithyroid drug** (Thionamide). It inhibits the enzyme thyroid peroxidase, preventing the synthesis of T3 and T4. It is a primary treatment for hyperthyroidism (Graves' disease). * **C. Ketoconazole:** This is an **imidazole antifungal** agent. It works by inhibiting the fungal enzyme 14-alpha-demethylase, blocking ergosterol synthesis. In high doses, it also inhibits steroid synthesis in humans (used in Cushing’s syndrome). * **D. Zidovudine (AZT):** This is a **Nucleoside Reverse Transcriptase Inhibitor (NRTI)** used in the treatment of HIV/AIDS. It inhibits viral DNA synthesis. **High-Yield Pearls for NEET-PG:** 1. **Levamisole Side Effect:** A classic board-favorite side effect is **agranulocytosis**. 2. **Other Immunostimulants:** Remember **Thalidomide** (used in ENL), **BCG vaccine** (used intravesically for bladder cancer), and **Interferons** (IFN-α for Hepatitis B/C). 3. **Levamisole "Adulterant":** It is frequently found as a contaminant in illicit cocaine, leading to a characteristic "retiform purpura" (skin necrosis).

Q: Liposomes are used for drug delivery in all of the following except?

Propranolol. Liposomes are microscopic spherical vesicles composed of a phospholipid bilayer surrounding an aqueous core. They are used as **targeted drug delivery systems** to enhance the therapeutic index, reduce systemic toxicity, and improve the solubility of drugs. **Why Propranolol is the Correct Answer:** Propranolol is a highly lipophilic, non-selective beta-blocker with excellent oral bioavailability and predictable pharmacokinetics [2], [3]. It does not require a specialized delivery system like liposomes for its clinical application. Liposomal technology is typically reserved for drugs with **high systemic toxicity** [1] or those requiring **targeted delivery** to specific tissues (like tumors or fungal cells). **Analysis of Incorrect Options:** * **Amphotericin-B:** Conventional Amphotericin-B is highly nephrotoxic. Liposomal Amphotericin-B (L-AMB) is the gold standard for reducing renal toxicity while maintaining efficacy against systemic fungal infections [1], [1]. * **Doxorubicin:** This chemotherapeutic agent is notorious for dose-limiting cardiotoxicity. Liposomal formulation (Pegylated) ensures the drug remains in the circulation longer and preferentially extravasates into tumor tissues, significantly reducing cardiac damage. * **Vincristine:** Liposomal vincristine improves the pharmacokinetics of the drug, allowing for higher dose intensity and better penetration into lymphoid tissues while potentially reducing peripheral neuropathy. **High-Yield Clinical Pearls for NEET-PG:** * **Stealth Liposomes:** These are coated with **Polyethylene Glycol (PEG)** to avoid detection by the Reticuloendothelial System (RES), thereby increasing the drug's half-life. * **Targeting:** Liposomes are particularly useful for targeting the **Liver and Spleen** (as they are naturally taken up by macrophages). * **Other Liposomal Drugs:** Daunorubicin, Cytarabine, and Morphine (extended-release epidural).

Q: Effects mediated by H1 histamine receptor include?

Maintenance of a wakeful state. **Explanation:** Histamine is a biogenic amine that acts through four types of G-protein coupled receptors ($H_1$ to $H_4$). Understanding the distribution and function of these receptors is high-yield for NEET-PG. **Why Option C is Correct:** $H_1$ receptors are widely distributed in the Central Nervous System (CNS), particularly in the tuberomammillary nucleus of the hypothalamus. Histaminergic neurons play a crucial role in the **maintenance of wakefulness and alertness**. This explains why first-generation antihistamines (like Diphenhydramine), which cross the blood-brain barrier and block central $H_1$ receptors, cause significant sedation. **Analysis of Incorrect Options:** * **Option A:** Gastric acid secretion is mediated by **$H_2$ receptors** located on the parietal cells of the stomach. $H_1$ receptors have no role in acid secretion. * **Option B:** Histamine does not induce hepatic enzymes. In fact, Cimetidine (an $H_2$ blocker) is a well-known **inhibitor** of the Cytochrome P450 system. * **Option C:** Activation of $H_1$ receptors typically causes **vasodilation** of arterioles (via nitric oxide release) and increased capillary permeability, leading to the "triple response." Vasoconstriction is not a primary effect of $H_1$ activation. **Clinical Pearls for NEET-PG:** 1. **$H_1$ Receptor Coupling:** It is a **$G_q$** protein-coupled receptor (activates the PLC-IP3/DAG pathway). 2. **Smooth Muscle:** $H_1$ stimulation causes bronchoconstriction and contraction of intestinal smooth muscle. 3. **Inverse Agonism:** Most "antihistamines" used clinically are technically inverse agonists rather than simple competitive antagonists. 4. **Second-Generation Antihistamines:** Drugs like Cetirizine and Loratadine are non-sedating because they have poor CNS penetration and high affinity for peripheral $H_1$ receptors.

Q: Monitoring of drug level is not required with which of the following medications?

L-Dopa. **Explanation:** The decision to perform **Therapeutic Drug Monitoring (TDM)** is based on the relationship between a drug’s plasma concentration and its clinical effect or toxicity. **Why L-Dopa is the correct answer:** L-Dopa is used in Parkinson’s disease, where the clinical response (improvement in motor symptoms) is easily observable and measurable at the bedside. TDM is generally **not required** when a drug has a **wide therapeutic index** or when its **pharmacodynamic effect can be easily monitored clinically** (e.g., blood pressure for antihypertensives, INR for warfarin, or motor scales for L-Dopa). **Analysis of Incorrect Options:** TDM is mandatory for the other options because they possess a **narrow therapeutic index**, where the dose required for efficacy is very close to the dose that causes toxicity. * **Lithium (A):** Has a very narrow window (0.6–1.2 mEq/L). Toxicity can lead to severe neurological and renal complications. * **Digoxin (C):** Used in heart failure and atrial fibrillation. Toxicity (arrhythmias, visual halos) occurs at levels slightly above the therapeutic range (0.5–2 ng/mL). * **Phenytoin (D):** Exhibits **zero-order (saturation) kinetics** at therapeutic doses. Small dose increments can lead to disproportionately large increases in plasma levels, causing ataxia and nystagmus. **High-Yield Clinical Pearls for NEET-PG:** * **Indications for TDM:** Narrow therapeutic index, poor correlation between dose and plasma level, non-compliance suspected, or drugs with saturable metabolism. * **Drugs requiring TDM (Mnemonic: "The LiPo DiT"):** **The**ophylline, **Li**thium, **P**henytoin, **D**igoxin, **I**mmunosuppressants (Cyclosporine), **T**ricyclic Antidepressants. * **Exceptions:** TDM is **not** done for drugs whose effects are irreversible (e.g., Aspirin) or easily measured (e.g., L-Dopa, Heparin via aPTT).

Q: Which of the following are NOT typically administered intradermally?

Insulin. **Explanation:** The **Intradermal (ID)** route involves injecting a drug into the dermis, the vascular layer of skin just below the epidermis. This route is characterized by slow absorption and is primarily used for diagnostic purposes or specific immunizations. **Why Insulin is the Correct Answer:** Insulin is typically administered via the **Subcutaneous (SC)** route. The subcutaneous tissue (fatty layer) has fewer blood vessels than muscle but more than the dermis, allowing for a slow, sustained, and predictable absorption rate. Injecting insulin intradermally would result in inconsistent absorption and potential skin irritation, while intramuscular injection would cause it to be absorbed too rapidly, risking hypoglycemia. **Analysis of Incorrect Options:** * **BCG Vaccine:** This is the classic example of an ID injection. It is administered over the left deltoid to induce a local cellular immune response, leaving a characteristic permanent scar. * **Test Dose of Drugs:** Sensitivity testing (e.g., for Penicillin) is done intradermally to observe for immediate hypersensitivity reactions (wheal and flare) while minimizing systemic exposure to the allergen. * **Mantoux Test:** Also known as the Tuberculin Skin Test (TST), it uses the ID route to inject PPD (Purified Protein Derivative) to screen for tuberculosis infection. **High-Yield NEET-PG Pearls:** * **Angle of Injection:** ID injections are given at a **10–15 degree angle** using a 26-27 gauge needle (tuberculin syringe). * **Volume:** The maximum volume for an ID injection is very small, usually **0.1 ml**. * **Rabies Vaccine:** Modern Post-exposure Prophylaxis (PEP) can be given via the ID route (Updated Thai Red Cross Regimen) to save costs in resource-limited settings. * **Insulin Sites:** Common SC sites include the abdomen (fastest absorption), thighs, and upper arms. Always rotate sites to prevent **lipodystrophy**.

Q: Which of the following routes of administration is shown in the given diagram?

Intradermal. ***Intradermal*** - Characterized by a **shallow needle angle of 10-15°** with the **needle tip positioned in the dermis** layer of the skin. - Results in **wheal or bleb formation** at the injection site due to the limited space in the dermal layer. *Subcutaneous* - Involves a **45° needle angle** with injection into the **subcutaneous tissue** beneath the dermis. - Uses **longer needles** than intradermal and does not produce wheal formation due to the loose connective tissue. *Intramuscular* - Requires a **90° needle angle** with **deeper penetration** into the muscle tissue. - Uses **longer needles (1-1.5 inches)** and targets muscles like the **deltoid** or **gluteus maximus**. *Intravenous* - Involves **direct insertion into a vein** with the needle **parallel to the vessel**. - Requires **visualization or palpation of veins** and immediate blood return upon needle insertion.

Question 1

Which of the following is a prodrug?

Accepted Answer

Levodopa

Answer

Amitriptyline

Answer

Primidone

Answer

Digitoxin

Question 2

Which of the following is an immunostimulant?

Accepted Answer

Levamisole

Answer

Methimazole

Answer

Ketoconazole

Answer

Zidovudine

Question 3

Which of the following statements is wrong?

Accepted Answer

Intra-arterial injection is a systemic route of drug administration.

Answer

Drugs should be highly lipid soluble to be administered transdermally.

Answer

Nitrates are given by sublingual route.

Answer

Parenteral route bypasses first-pass metabolism.

Question 4

Liposomes are used for drug delivery in all of the following except?

Accepted Answer

Propranolol

Answer

Amphotericin-B

Answer

Doxorubicin

Answer

Vincristine

Question 5

Effects mediated by H1 histamine receptor include?

Accepted Answer

Maintenance of a wakeful state

Answer

Inhibition of gastric acid secretion

Answer

Induction of hepatic cytochrome P450 enzyme

Answer

Vasoconstriction of arterioles

Question 6

Monitoring of drug level is not required with which of the following medications?

Accepted Answer

L-Dopa

Answer

Lithium

Answer

Digoxin

Answer

Phenytoin

Question 7

Which of the following are NOT typically administered intradermally?

Accepted Answer

Insulin

Answer

BCG vaccine

Answer

Test dose of drugs

Answer

Mantoux test

Question 8

Which of the following routes of administration is shown in the given diagram?

Accepted Answer

Intradermal

Answer

Subcutaneous

Answer

Intramuscular

Answer

Intravenous

Question 9

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

Accepted Answer

Metformin

Answer

Phenytoin

Answer

Tacrolimus

Answer

Cyclosporin

Question 10

Which of the following actions is not caused by H1 receptor?

Accepted Answer

Gastric acid secretion

Answer

Vasoconstriction

Answer

Increased capillary permeability

Answer

Bronchoconstriction

General Pharmacology — MCQs

General Pharmacology — MCQs

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