Answer: B. Circulating antibodies that block ACh receptors at the postsynaptic neuromuscular junction

Explanation: Myasthenia gravis is an autoimmune disorder in which antibodies target and block acetylcholine receptors at the neuromuscular junction, impairing signal transmission and muscle function.

Answer: B. Binding to a site other than the active binding site on the same enzyme

Explanation: Allosteric binding occurs when a molecule binds at a site different from the active site, thereby modulating the enzyme's activity.

Answer: A. α-glycoprotein

Explanation: α-glycoprotein plays a key role in binding and distributing basic drugs throughout the body, thereby influencing their bioavailability and therapeutic effectiveness.

Answer: D. Tocilizumab

Explanation: Tocilizumab was approved by the US-FDA for rheumatoid arthritis treatment in 2010, offering an effective option for managing the disease.

Answer: D. Lithium

Explanation: Lithium is primarily used for bipolar disorder, not schizophrenia. Antipsychotics like haloperidol are correct.

Answer: D. All

Explanation: All the drugs listed (Citalopram, Fluxetin, and Sertraline) are selective serotonin reuptake inhibitors (SSRIs) that increase serotonin levels, helping to alleviate symptoms of depression.

Answer: D. All

Explanation: SIBUTRAMIN is noted for all these characteristics: it acts as a serotonin-norepinephrine reuptake inhibitor, was used as an adjunct in obesity treatment, and was withdrawn from the market because of cardiotoxicity.

Answer: D. All

Explanation: Antiparkinsonian drugs act through multiple mechanisms including increasing dopamine activity and reducing acetylcholine activity, both contributing to improved motor function.

Answer: A. Furosemide

Explanation: Furosemide, a loop diuretic, is known to cause ototoxicity. This side effect, particularly at high or rapid doses, can lead to hearing loss or balance disturbances.

Answer: B. Ototoxicity

Explanation: Gentamicin, an aminoglycoside, is notorious for causing ototoxicity. This side effect can lead to hearing loss and balance issues, making it a well-documented clinical concern.

Answer: D. None of the above

Explanation: Chloramphenicol does not belong to the beta-lactams, aminoglycosides, or macrolides. It is a broad-spectrum antibiotic with a distinct mechanism from these classes.

Answer: B. Protein synthesis

Explanation: Erythromycin works by inhibiting protein synthesis in bacteria, which disrupts their ability to grow and multiply, making it effective against many bacterial infections.

Answer: B. Inhibits DNA-dependent RNA polymerase

Explanation: Rifampicin targets and inhibits DNA-dependent RNA polymerase, which is essential for bacterial RNA synthesis and growth.

Answer: A. Biguanides

Explanation: Metformin is classified as a biguanide. It works by reducing hepatic glucose production and increasing insulin sensitivity, making it a first-line treatment for type 2 diabetes.

Answer: B. Competitive inhibitors of the enzyme dihydropteroate synthetase (DHPS)

Explanation: Sulfonamides work by competitively inhibiting DHPS, an enzyme crucial for folate synthesis in bacteria, thereby stopping their growth.

Answer: A. Competitively inhibits dihydrofolate synthetase (DHFS)

Explanation: Methotrexate inhibits DHFR, not DHFS.

Answer: B. Erythrityl trinitrate

Explanation: Correct antidotes are sodium nitrite and sodium thiosulfate.

Answer: A. Glimepiride

Explanation: Glimepiride is classified as a third-generation hypoglycaemic agent because it effectively stimulates insulin secretion with a lower risk of hypoglycemia.

Answer: C. Increase frequency of chloride channel

Explanation: GABA increases the frequency of chloride channel opening, leading to neuronal hyperpolarization and inhibition in the central nervous system.

Answer: A. Slowly metabolised by acetyl cholinesterase

Explanation: Succinylcholine remains bound to nicotinic receptors longer because it is metabolised more slowly by acetylcholinesterase compared to acetylcholine.