General Pharmacology — MCQs

General Pharmacology Indian Medical PG Practice Questions and MCQs

Question 551: Tachyphylaxis is seen with which of the following drugs?

A. Pethidine
B. Phenoxybenzamine
C. Phentolamine
D. Ephedrine (Correct Answer)

Explanation: ***Ephedrine*** - **Ephedrine** is an indirectly acting sympathomimetic that releases stored norepinephrine from nerve terminals [1, 3]. This can lead to **tachyphylaxis** (rapidly decreasing response to repeated doses) as **norepinephrine stores** become depleted [2, 3]. - Due to the depletion of **neurotransmitter stores**, subsequent doses become less effective until stores are replenished [2, 3]. *Pethidine* - **Pethidine** is an opioid analgesic; its primary mechanism of action involves agonizing opioid receptors. - It does not typically exhibit **tachyphylaxis** through neurotransmitter depletion, but rather can lead to tolerance with chronic use. *Phenoxybenzamine* - **Phenoxybenzamine** is a non-selective, **irreversible alpha-adrenergic receptor blocker**. - Its mechanism involves long-lasting blockade of receptors, and **tachyphylaxis** is not a characteristic feature of its pharmacodynamics. *Phentolamine* - **Phentolamine** is a non-selective, **reversible alpha-adrenergic receptor blocker**. - While it has a shorter duration of action compared to phenoxybenzamine, its effects are reversible and it does not typically cause **tachyphylaxis** through neurotransmitter depletion.

Question 552: Mechanism of action of Niclosamide is:

A. Inhibition of substrate level phosphorylation
B. Inhibition of proton efflux pumps
C. Increase production of free radicals
D. Inhibition of mitochondrial oxidative phosphorylation (Correct Answer)

Explanation: ***Inhibition of mitochondrial oxidative phosphorylation*** - **Niclosamide** is an **uncoupler of oxidative phosphorylation**, leading to **ATP depletion** in the parasite. - This effectively starves the parasite of energy, particularly **tapeworms**, which are highly dependent on this pathway. *Inhibition of substrate level phosphorylation* - **Substrate-level phosphorylation** is a metabolic pathway that directly phosphorylates ADP to ATP using high-energy intermediate molecules, not the primary target of niclosamide. - While it contributes to ATP production, its inhibition is not the primary mechanism of action for **niclosamide**. *Inhibition of proton efflux pumps* - **Proton efflux pumps** (e.g., proton pumps in gastric cells) are generally not the direct target for anthelmintic drugs like niclosamide. - This mechanism is characteristic of drugs like **proton pump inhibitors** (PPIs) used to reduce stomach acid. *Increase production of free radicals* - Some antiparasitic drugs act by increasing **oxidative stress** and **free radical production**, leading to parasite death. - However, for **niclosamide**, the primary mechanism is the disruption of **ATP synthesis** through uncoupling.

Question 553: Tibolone is a ?

A. Natural steroidal hormone
B. Natural non-steroidal hormone
C. Synthetic steroid hormone (Correct Answer)
D. Synthetic non-steroidal hormone

Explanation: ***Synthetic steroid hormone*** - **Tibolone** is a **synthetic steroid** with **estrogenic, progestogenic, and weak androgenic properties** used for hormone therapy in postmenopausal women. - Its structure is derived from **nortestosterone**, making it a synthetic compound rather than naturally occurring. *Natural steroidal hormone* - Natural steroidal hormones like **estrogen** and **progesterone** are produced endogenously by the body and have specific steroidal molecular structures. - Tibolone is not a naturally occurring hormone but is manufactured in a lab. *Natural non-steroidal hormone* - Natural non-steroidal hormones typically include peptides (e.g., insulin) or amines (e.g., thyroid hormones). - Tibolone's chemical structure is clearly steroidal, not non-steroidal. *Synthetic non-steroidal hormone* - Synthetic non-steroidal hormones are compounds like **diethylstilbestrol** (DES) that mimic hormone action but lack the steroid nucleus. - Tibolone possesses a distinct steroid backbone, classifying it as a synthetic steroid.

Question 554: What is the active principle of the plant Calotropis?

A. Calotropin (Correct Answer)
B. Emodin
C. Ricin
D. Plumbagin

Explanation: ***Calotropin*** - **Calotropin** is the primary **cardiac glycoside** found in the latex of the *Calotropis* plant, responsible for its toxic and medicinal properties. - This compound exerts its effects by inhibiting the **Na+/K+-ATPase pump**, leading to increased intracellular calcium and potentially cardiotoxicity. *Plumbagin* - **Plumbagin** is a **naphthoquinone** derivative found in plants like *Plumbago zeylanica*, known for its antimicrobial and anticancer activities. - It is not associated with *Calotropis* and has a different chemical structure and mechanism of action compared to cardiac glycosides. *Ricin* - **Ricin** is a highly potent **protein toxin** derived from the seeds of the **castor bean plant** (*Ricinus communis*). - Its mechanism involves inhibiting protein synthesis, which is distinct from the cardiac glycoside action of *Calotropis*. *Emodin* - **Emodin** is an **anthraquinone** derivative commonly found in plants such as **rhubarb** and **aloe**, known for its laxative and anti-inflammatory properties. - It is structurally and functionally different from the cardiac glycosides found in *Calotropis*.

Question 555: Tocilizumab acts as an antagonist at which receptor?

A. IL-1
B. IL-2
C. IL-6 (Correct Answer)
D. TNF-alpha

Explanation: ***Correct: IL-6*** - **Tocilizumab** is a **monoclonal antibody** that specifically targets the **IL-6 receptor**, blocking the binding of **interleukin-6 (IL-6)** and inhibiting its pro-inflammatory effects. - This mechanism makes it effective in treating inflammatory conditions like **rheumatoid arthritis**, **giant cell arteritis**, and **cytokine release syndrome**. *Incorrect: IL-1* - **IL-1 antagonists**, such as **anakinra**, target the **IL-1 receptor** to block the inflammatory actions of **interleukin-1**. - These are typically used for conditions like **rheumatoid arthritis** and **cryopyrin-associated periodic syndromes (CAPS)**, distinct from tocilizumab's mechanism. *Incorrect: IL-2* - **IL-2 receptor antagonists**, such as **basiliximab** and **daclizumab**, are primarily used to prevent **organ transplant rejection** by inhibiting **T-cell activation**. - Their mechanism is different from **tocilizumab**, which targets a different cytokine pathway. *Incorrect: TNF-alpha* - **TNF-alpha inhibitors**, like **adalimumab** or **infliximab**, block the activity of **tumor necrosis factor-alpha**, a key cytokine in inflammation. - These agents are widely used for diseases such as **rheumatoid arthritis**, **psoriasis**, and **Crohn's disease**, but they operate on a different pathway than tocilizumab.

Question 556: Highest cannabinoid content of cannabis is found in which part of the plant?

A. Root
B. Resin (Correct Answer)
C. Seed
D. Stem

Explanation: ***Resin*** - The **resin** (often called **kief** or hashish when processed) is a sticky, viscous substance produced by glandular trichomes, which are most abundant on the female cannabis flower. - This resin contains the highest concentration of **cannabinoids**, including **THC** (tetrahydrocannabinol), which is responsible for the plant's psychoactive effects. *Root* - The **root** of the cannabis plant contains very minimal amounts of cannabinoids. - Its primary function is in nutrient and water absorption, and anchoring the plant. *Seed* - **Cannabis seeds** are rich in oils, proteins, and omega fatty acids, but they contain negligible amounts of psychoactive cannabinoids. - They are primarily used for cultivation or as a nutritional food source (hemp seeds). *Stem* - The **stem** of the cannabis plant mainly consists of fibrous material and woody tissue. - While it may contain trace amounts of cannabinoids, the concentration is significantly lower compared to the resinous parts.

Question 557: Which of the following drug classes is not typically considered a first-line treatment for chronic pain management?

A. Opioids
B. Antiepileptics
C. Serotonergic drugs
D. Dopamine antagonist (Correct Answer)

Explanation: ***Dopamine antagonist*** - **Dopamine antagonists** (e.g., metoclopramide, haloperidol) are primarily used for treating conditions like **psychosis, nausea, and vomiting**, and are **not used for chronic pain management**. - While dopamine pathways can influence pain perception, directly blocking dopamine receptors is not a recognized approach for managing chronic pain and can cause significant adverse effects (extrapyramidal symptoms, sedation). - This is the **correct answer** as they are definitively not first-line (or even considered) for chronic pain. *Opioids* - While **opioids** can be effective for moderate to severe pain, **current guidelines do NOT recommend them as first-line for chronic non-cancer pain** due to risks of addiction, tolerance, and limited long-term efficacy. - However, they may be considered in specific circumstances after other treatments fail, so they are not the best answer here since dopamine antagonists are never used. - First-line options are typically non-opioid analgesics (NSAIDs, acetaminophen) for nociceptive pain. *Antiepileptics* - **Antiepileptics** (e.g., **gabapentin, pregabalin**) are **first-line treatments for neuropathic chronic pain**. - They work by modulating voltage-gated calcium channels and reducing neurotransmitter release, which helps calm overactive nerve signals. - Widely recommended in guidelines for diabetic neuropathy, postherpetic neuralgia, and other neuropathic conditions. *Serotonergic drugs* - **Serotonergic drugs**, particularly **SNRIs** (e.g., **duloxetine, venlafaxine**) and **tricyclic antidepressants** (e.g., amitriptyline), are **first-line agents for several chronic pain conditions**. - Used for fibromyalgia, chronic musculoskeletal pain, and neuropathic pain. - They enhance descending inhibitory pain pathways by increasing serotonin and norepinephrine at the spinal cord level.

Question 558: Which vaccine should not be frozen?

A. OPV
B. Measles
C. HBV (Correct Answer)
D. Yellow fever

Explanation: ***HBV*** - **Hepatitis B vaccine** (HBV) contains an **aluminum adjuvant** (aluminum hydroxide or aluminum phosphate), which is **irreversibly damaged by freezing**. - Freezing causes the adjuvant to form **large aggregates**, leading to loss of **potency and immunogenicity**, rendering the vaccine ineffective. - **WHO and CDC guidelines** strictly prohibit freezing of aluminum-adjuvanted vaccines. *OPV* - **Oral polio vaccine** (OPV) is a **live attenuated vaccine** that is **stable when frozen**. - It is stored at **-20°C for long-term storage** to maintain its **viability over extended periods**. - Freezing is **recommended** for OPV preservation. *Measles* - The **measles vaccine** should ideally be **stored at 2-8°C** and **not frozen** according to standard guidelines. - However, measles vaccine is **more freeze-tolerant** than aluminum-adjuvanted vaccines and some formulations can withstand brief freezing. - **HBV remains the classic answer** for vaccines that should not be frozen due to the aluminum adjuvant sensitivity. *Yellow fever* - The **yellow fever vaccine** is a **live attenuated vaccine** that is **stable when frozen**. - Stored at **-20°C or colder** for long-term storage to preserve its **potency and effectiveness**. - Freezing is **recommended** for yellow fever vaccine preservation.

Question 559: Which of the following actions are associated with Danazol?

A. Weak androgenic
B. Progestational
C. Anabolic
D. All of the options (Correct Answer)

Explanation: ***All of the options*** - **Danazol** is a synthetic steroid with a variety of hormonal activities, including **weak androgenic**, **anabolic**, and **progestational** effects. - Its diverse pharmacological profile contributes to its therapeutic uses, particularly in conditions like **endometriosis** and **fibrocystic breast disease**, where it suppresses gonadotropin release and ovarian function. - All three properties listed (androgenic, progestational, and anabolic) are characteristics of Danazol. **Weak androgenic activity:** - Danazol possesses **weak androgenic activity**, meaning it can bind to androgen receptors and exert effects similar to, but less potent than, testosterone. - This can lead to side effects such as **hirsutism**, **acne**, and **voice deepening** in some patients. **Progestational activity:** - While not its primary action, Danazol has some **progestational properties** due to its steroid structure, contributing to its ability to suppress the hypothalamic-pituitary-ovarian axis. - This activity helps in creating a **hypoestrogenic state**, which is beneficial in treating conditions like endometriosis. **Anabolic activity:** - Danazol has **anabolic effects**, promoting protein synthesis and muscle growth, similar to other anabolic steroids. - This property is utilized in treating **hereditary angioedema** by increasing C1 esterase inhibitor levels. - This can lead to side effects like **weight gain** and changes in **lipid profiles**.

Question 560: Most effective agent to prevent motion sickness is?

A. Ephedrine
B. Nedocromil
C. Cyproheptidine
D. Hyoscine (Correct Answer)

Explanation: ***Hyoscine*** - **Hyoscine (scopolamine)** is an anticholinergic drug that works by blocking muscarinic receptors in the **vestibular system** and **vomiting center**, making it highly effective for preventing motion sickness [1], [2]. - It is often administered as a **transdermal patch** for sustained release, providing convenience and prolonged efficacy [1], [2]. *Ephedrine* - **Ephedrine** is a sympathomimetic drug primarily used as a decongestant and bronchodilator. - While it has some central nervous system effects, it is **not considered a primary or effective agent** for preventing motion sickness. *Nedocromil* - **Nedocromil** is a mast cell stabilizer used in the treatment of asthma and allergic conjunctivitis. - Its mechanism of action involves **inhibiting the release of inflammatory mediators**, which is unrelated to the physiological pathways of motion sickness. *Cyproheptidine* - **Cyproheptidine** is a first-generation antihistamine with anticholinergic and antiserotonergic properties. - While some antihistamines can relieve motion sickness, cyproheptidine is mainly used for **allergic conditions** and as an **appetite stimulant**, and is not the most effective choice for motion sickness prevention [3].

Practice by Chapter

Pharmacokinetics: Absorption and Distribution

Practice Questions

Pharmacokinetics: Metabolism and Excretion

Practice Questions

Pharmacodynamics and Receptor Theory

Practice Questions

Drug-Receptor Interactions and Dose-Response

Practice Questions

Pharmacogenetics and Personalized Medicine

Practice Questions

Adverse Drug Reactions and Toxicity

Practice Questions

Drug Interactions

Practice Questions

Drug Development and Regulation

Practice Questions

Pediatric and Geriatric Pharmacology

Practice Questions

Placental Transfer and Lactation

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free