GPAT Pharmaceutical Chemistry Syllabus

What is the difference between a limit test and an assay?

A limit test is a qualitative/semi-quantitative test to determine that an impurity does not exceed a specified limit, whereas an assay quantitatively determines the actual amount of active ingredient present.

Define an isotope.

Atoms of the same element that have the same atomic number (number of protons) but different mass numbers due to a different number of neutrons.

What is a radioisotope (radionuclide)?

An unstable isotope that undergoes radioactive decay, emitting radiation (alpha, beta, or gamma) to become more stable; used in diagnosis and therapy.

What is the radioisotope of iodine used in thyroid imaging and therapy, and its emission?

Iodine-131 (I-131); it emits both beta and gamma radiation and is used to diagnose and treat thyroid disorders including thyroid cancer and hyperthyroidism.

Which is the most widely used radioisotope in nuclear medicine imaging, and why?

Technetium-99m (Tc-99m); it emits pure gamma radiation, has a short half-life (~6 hours), and is ideal for diagnostic imaging with minimal radiation dose.

Define half-life of a radioisotope.

The time required for half of the radioactive atoms in a sample to disintegrate (decay), a constant value characteristic of each radioisotope.

What is the SI unit of radioactivity, and the older unit?

The SI unit is the becquerel (Bq), equal to one disintegration per second; the older unit is the curie (Ci), where 1 Ci = 3.7 x 10^10 Bq.

Which carbon isotope is used in radiocarbon dating, and its approximate half-life?

Carbon-14 (C-14), with a half-life of about 5730 years.

Name a phosphorus radioisotope used therapeutically and its application.

Phosphorus-32 (P-32), a beta emitter used in the treatment of polycythemia vera and certain leukemias.

What is a pharmacopoeial monograph?

An official document in a pharmacopoeia that gives the standards (name, description, identification, purity, assay, storage, labeling) for a specific drug substance or product.

List the typical sections/components of a drug monograph in the pharmacopoeia.

Title/name, molecular formula and weight, structure, definition, category, description, solubility, identification tests, tests for purity (limit tests), assay, storage conditions, and labeling.

What does 'standard of purity' in a monograph specify, expressed as percentage?

The minimum and/or maximum percentage of the active substance that must be present (e.g., 'not less than 98.0% and not more than 102.0% calculated on the dried basis').

What is the principal Indian official compendium containing drug monographs?

The Indian Pharmacopoeia (IP), published by the Indian Pharmacopoeia Commission.

What is the difference between 'description' and 'identification' in a monograph?

'Description' gives physical characteristics (appearance, odor, color, taste, solubility), whereas 'identification' provides specific chemical/physical tests to confirm the identity of the substance.

What are antacids, and give an example with its action?

Antacids neutralize gastric hydrochloric acid to relieve hyperacidity; e.g., aluminium hydroxide and magnesium hydroxide react with HCl to form salt and water, raising gastric pH.

What therapeutic class do sulphonamides belong to, and how do they act?

Antibacterial (antimicrobial) agents; they are bacteriostatic, acting by competitively inhibiting dihydropteroate synthase, blocking folic acid synthesis in bacteria (PABA antagonists).

Define antineoplastic (anticancer) agents and give a class example.

Agents used to treat cancer by killing or inhibiting proliferation of malignant cells; classes include alkylating agents (e.g., cyclophosphamide), antimetabolites (e.g., methotrexate), and antibiotics (e.g., doxorubicin).

What are antihistamines, and into which two main classes are they divided?

Drugs that block histamine receptors; H1-antagonists (e.g., chlorpheniramine, used in allergy) and H2-antagonists (e.g., ranitidine, used to reduce gastric acid).

What is the therapeutic class of diazepam, and its mechanism?

A benzodiazepine anxiolytic/sedative-hypnotic; it potentiates GABA action at GABA-A receptors, increasing chloride ion influx and producing CNS depression.

Classify analgesics into their main categories.

Opioid (narcotic) analgesics, e.g., morphine; and non-opioid (non-narcotic) analgesics including NSAIDs, e.g., aspirin and ibuprofen.

How do NSAIDs produce their anti-inflammatory and analgesic effect?

By inhibiting cyclooxygenase (COX) enzymes, thereby blocking the synthesis of prostaglandins that mediate pain, inflammation, and fever.

What is the therapeutic class of furosemide, and where does it act?

A loop diuretic; it acts on the thick ascending limb of the loop of Henle, inhibiting the Na+/K+/2Cl- cotransporter to increase urine output.

Name the major classes of antihypertensive drugs.

Diuretics, beta-blockers, calcium channel blockers, ACE inhibitors, angiotensin receptor blockers (ARBs), and centrally acting/alpha-blockers.

What is the mechanism of action of ACE inhibitors, and give an example?

They inhibit angiotensin-converting enzyme, preventing conversion of angiotensin I to angiotensin II, causing vasodilation and lowering blood pressure; e.g., captopril, enalapril.

What therapeutic class is metformin, and how does it act?

An oral antidiabetic (biguanide); it lowers blood glucose mainly by decreasing hepatic gluconeogenesis and increasing peripheral insulin sensitivity.

What are beta-lactam antibiotics, and what is their mechanism?

Antibiotics containing a beta-lactam ring (penicillins, cephalosporins); they inhibit bacterial cell wall synthesis by binding penicillin-binding proteins and blocking transpeptidation.

What is the therapeutic class of omeprazole, and its mechanism?

A proton pump inhibitor (PPI); it irreversibly inhibits the H+/K+-ATPase enzyme of gastric parietal cells, strongly suppressing gastric acid secretion.

Differentiate between bactericidal and bacteriostatic agents.

Bactericidal agents kill bacteria (e.g., penicillins, aminoglycosides), whereas bacteriostatic agents inhibit bacterial growth and multiplication, allowing host defenses to clear them (e.g., tetracyclines, sulphonamides).

What are anticoagulants, and give two examples with different mechanisms?

Drugs that prevent blood clotting; heparin acts by enhancing antithrombin III activity (parenteral), while warfarin inhibits vitamin K-dependent clotting factor synthesis (oral).

What class of drugs are statins, and how do they lower cholesterol?

Antihyperlipidemic agents (HMG-CoA reductase inhibitors); they inhibit HMG-CoA reductase, the rate-limiting enzyme of cholesterol biosynthesis, lowering LDL cholesterol; e.g., atorvastatin.