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ESIC Pharmacist Recruitment Exam study materials
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ESIC Pharmacist Recruitment Exam practice questions

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Question 1Pharmaceutics

According to the Indian Pharmacopoeia, a tablet described as 'dispersible' must disintegrate in water within which time limit at 15–25 °C?

  1. 30 minutes
  2. 3 minutes Correct answer.
  3. 60 minutes
  4. 15 minutes

Explanation

Dispersible tablets are defined by a disintegration limit of 3 minutes in water maintained at 15–25 °C, which ensures the dispersion is suitable for oral administration as a suspension. This is a distinct monograph requirement and should not be confused with the limits for uncoated (15 minutes) or film-coated (30 minutes) tablets.

Question 2Pharmaceutics

In the manufacture of hard gelatin capsules on a rotary die machine, which component is primarily responsible for forming the capsule shell around the rotating pins?

  1. The pin bars dipping into the gelatin bath
  2. The wedge-shaped segment Correct answer.
  3. The loading hopper
  4. The air blast at the transfer station

Explanation

The wedge-shaped segment delivers molten gelatin from the bath onto the rotating pins, where surface tension and the pin geometry shape the cap and body. The pins themselves are dipped but the wedge controls the film formation and gelatin distribution.

Question 3Pharmaceutics

Which excipient is added to a tablet formulation specifically to promote the breakup of the tablet into granules and then primary particles in the gastrointestinal tract?

  1. Glidant
  2. Lubricant
  3. Binder
  4. Disintegrant Correct answer.

Explanation

A disintegrant draws water into the tablet matrix by capillary action and swelling, causing the compact to break apart and release the drug for dissolution. Binders promote cohesion, glidants improve powder flow, and lubricants reduce friction during compression, none of which serve disintegration.

Question 4Pharmaceutics

Which route of administration is defined as placing a dosage form under the tongue for rapid systemic absorption through the sublingual mucosa?

  1. Intranasal
  2. Rectal
  3. Buccal
  4. Sublingual Correct answer.

Explanation

Sublingual administration places the dosage form beneath the tongue, where the thin, highly vascularised mucosa allows rapid absorption directly into the systemic circulation, bypassing first-pass hepatic metabolism. Buccal administration uses the inner cheek, which is a distinct site with slower absorption.

Question 5Pharmaceutics

Which of the following describes the primary purpose of a coating applied to an enteric-coated tablet?

  1. To provide immediate release in the stomach
  2. To delay drug release until the dosage form reaches the intestine Correct answer.
  3. To improve tablet elegance and colour
  4. To mask an unpleasant taste during swallowing

Explanation

Enteric coatings are pH-sensitive polymers such as cellulose acetate phthalate or Eudragit L that remain intact in gastric acid and dissolve at the higher pH of the small intestine. This protects acid-labile drugs and prevents gastric irritation.

Question 6Pharmaceutics

Which of the following best defines 'bioavailability' as used in pharmaceutics?

  1. The concentration of drug bound to plasma proteins
  2. The rate and extent to which the active moiety enters systemic circulation Correct answer.
  3. The total amount of drug excreted unchanged in urine
  4. The volume of plasma cleared of drug per unit time

Explanation

Bioavailability describes both the rate and the extent of absorption of an unchanged drug from a dosage form into the systemic circulation. It is expressed as absolute bioavailability (compared with intravenous) or relative bioavailability (compared with another reference product).

Question 7Pharmaceutics

Which of the following is the correct standard expression of Fick's first law of diffusion for a drug across a membrane of thickness h?

  1. J = (C1 − C2)·h/(D·A)
  2. J = D·A·h/(C1 − C2)
  3. J = D·h/(A·(C1 − C2))
  4. J = D·A·(C1 − C2)/h Correct answer.

Explanation

Fick's first law states that the flux J is proportional to the diffusion coefficient D, the area A, and the concentration gradient (C1 − C2)/h. Therefore J = D·A·(C1 − C2)/h.

Question 8Pharmaceutics

Which of the following is the accepted definition of a 'suspension' in pharmaceutics?

  1. A coarse dispersion in which insoluble solid particles are dispersed in a liquid medium Correct answer.
  2. A solid dispersion of drug in a polymer matrix
  3. A thermodynamically stable system of two immiscible liquids
  4. A clear, homogeneous mixture of two miscible liquids

Explanation

A pharmaceutical suspension is a coarse dispersion of insoluble solid particles in a liquid medium, usually aqueous, and is thermodynamically unstable, requiring suspending agents and controlled flocculation to maintain uniformity. It is not a solution or an emulsion.

Question 9Pharmaceutics

A pharmacist needs to prepare 500 mL of a 2% w/v solution of a drug from a 10% w/v stock solution. What volume of stock solution is required?

  1. 150 mL
  2. 100 mL Correct answer.
  3. 200 mL
  4. 50 mL

Explanation

Using the dilution equation C1V1 = C2V2: 10% × V1 = 2% × 500 mL, so V1 = 100 mL. The remaining volume (400 mL) is made up with the appropriate solvent.

Question 10Pharmaceutics

A prescription requires 120 mg of codeine phosphate per 5 mL of syrup, and the syrup is to be dispensed in a 200 mL bottle. What mass of codeine phosphate must be weighed?

  1. 4.8 g Correct answer.
  2. 1.2 g
  3. 2.4 g
  4. 9.6 g

Explanation

The concentration is 120 mg per 5 mL, so there are 24 mg/mL. For 200 mL: 24 × 200 = 4800 mg = 4.8 g.

Question 11Pharmaceutics

Which mechanism best explains why adding a small quantity of a flocculating electrolyte such as sodium chloride stabilises a pharmaceutical suspension?

  1. It increases the zeta potential, increasing electrostatic repulsion
  2. It increases the viscosity of the continuous phase
  3. It reduces the zeta potential so particles form loose flocs that sediment rapidly but redisperse easily Correct answer.
  4. It dissolves the dispersed particles

Explanation

Flocculating electrolytes compress the electrical double layer, reducing the zeta potential to a level where van der Waals attraction predominates, so particles form loose flocs. These flocs sediment rapidly but do not form a hard cake and are easily redispersed on shaking.

Question 12Pharmaceutics

Which of the following best explains the purpose of the 'calibration' of a tablet compression machine?

  1. To determine the expiry date of the tablets
  2. To colour the tablets uniformly
  3. To sterilise the compression chamber
  4. To verify that the punches and dies are correctly set so that tablets of consistent weight and hardness are produced Correct answer.

Explanation

Calibration of a tablet press ensures that the dies are filled consistently and that the compression force is correctly set, producing tablets of uniform weight, thickness and hardness. It is a quality-control step in manufacture, not a sterilisation or cosmetic step.

Question 13Pharmaceutics

Which of the following describes the correct order of stages in the wet granulation process?

  1. Addition of binder solution → mixing → compression → drying
  2. Mixing of drug and excipients → addition of binder solution → wet massing → drying → milling → compression Correct answer.
  3. Mixing of drug and excipients → drying → addition of binder solution → wet massing → compression
  4. Mixing → compression → wet massing → drying

Explanation

Wet granulation begins with dry mixing of drug and excipients, followed by addition of the binder solution and wet massing to form granules. The wet mass is dried, milled to a uniform size, and finally compressed into tablets.

Question 14Pharmaceutics

In a first-order degradation reaction, the shelf life (t90) of a drug product is best described as:

  1. The time taken for 50% of the drug to degrade
  2. The time taken for the drug to reach 90% of its initial concentration
  3. The time taken for the drug to completely degrade
  4. The time taken for 10% of the drug to degrade Correct answer.

Explanation

The t90, or shelf life, is the time for the drug concentration to fall to 90% of its initial value, i.e. 10% degradation. For a first-order reaction, t90 = 0.105/k.

Question 15Pharmaceutics

A drug has an elimination half-life of 6 hours. Approximately what fraction of the steady-state plasma concentration is reached after 24 hours of a constant-rate infusion?

  1. 75%
  2. 100%
  3. 50%
  4. 94% Correct answer.

Explanation

After 24 hours, four half-lives (24/6) have elapsed. The fraction of steady state reached is 1 − (1/2)^4 = 1 − 0.0625 = 0.9375, i.e. about 94%.

Question 16Pharmaceutics

Which statement correctly describes the role of the 'wedge' in a rotary capsule-filling machine?

  1. It compresses the powder into a slug
  2. It scrapes excess powder from the capsule body
  3. It seals the capsule after filling
  4. It supplies molten gelatin to the pins Correct answer.

Explanation

In rotary die capsule manufacture, the wedge-shaped segment dips into the gelatin bath and delivers molten gelatin to the rotating pins to form the cap and body. It is a shell-forming component, not a powder-handling component.

Question 17Pharmaceutics

A pharmacist prepares a suppository using the fusion method with a mould calibrated for cocoa butter (density factor 1.0). The drug has a density factor of 1.5. If the mould holds 2 g of cocoa butter and 0.4 g of drug is to be incorporated, what mass of cocoa butter base is required?

  1. 1.87 g
  2. 2.00 g
  3. 1.60 g
  4. 1.73 g Correct answer.

Explanation

The displacement value is calculated as drug mass / density factor = 0.4 / 1.5 = 0.267 g of base displaced. Base required = 2.0 − 0.267 = 1.73 g.

Question 18Pharmaceutics

Which of the following is the most appropriate reason for adding a chelating agent such as disodium edetate to a pharmaceutical formulation?

  1. To act as a primary antioxidant
  2. To bind trace metal ions that catalyse oxidative degradation Correct answer.
  3. To increase the solubility of the drug in water
  4. To adjust the pH of the formulation

Explanation

Disodium edetate chelates trace transition-metal ions such as iron and copper that catalyse oxidative degradation of drugs, thereby improving stability. It is a synergistic additive used alongside antioxidants, not a primary antioxidant or pH adjuster.

Question 19Pharmaceutics

A formulation contains 0.5% w/w of a preservative in a cream. If the cream is prepared in a 500 g batch, what mass of preservative is required?

  1. 0.25 g
  2. 25 g
  3. 5.0 g
  4. 2.5 g Correct answer.

Explanation

0.5% w/w means 0.5 g per 100 g, so for 500 g the mass is 0.5 × 5 = 2.5 g.

Question 20Pharmaceutics

Which of the following is the primary reason for using a lyophilisation (freeze-drying) process for an injectable product?

  1. To reduce the cost of packaging
  2. To increase the solubility of the drug
  3. To sterilise the product by heat
  4. To produce a dry, stable powder that is reconstituted immediately before use Correct answer.

Explanation

Freeze-drying removes water by sublimation under low temperature and pressure, producing a dry powder that is stable for storage and is reconstituted with a suitable diluent immediately before injection. It is not a sterilisation or solubilisation process.

Question 21Pharmaceutics

In the context of the Biopharmaceutics Classification System (BCS), a drug belonging to Class II is best described as:

  1. High solubility, low permeability
  2. Low solubility, low permeability
  3. High solubility, high permeability
  4. Low solubility, high permeability Correct answer.

Explanation

BCS Class II comprises drugs with low aqueous solubility and high intestinal permeability. Their absorption is limited by dissolution rate, making them candidates for formulation strategies such as particle-size reduction or solid dispersions.

Question 22Pharmaceutics

A drug follows zero-order elimination. Which statement about its elimination half-life is correct?

  1. The half-life is proportional to the initial concentration Correct answer.
  2. The half-life is inversely proportional to the elimination rate constant
  3. The half-life is equal to 0.693/k
  4. The half-life is constant and independent of dose

Explanation

In zero-order kinetics the rate of elimination is constant, so the time to halve the concentration depends on the starting concentration: t1/2 = C0/(2k0). Thus the half-life is proportional to the initial concentration and increases as the dose increases.

Question 23Pharmaceutics

Which of the following best explains why a solid dispersion can enhance the dissolution rate of a poorly water-soluble drug?

  1. The drug is molecularly dispersed or present as an amorphous solid, increasing its apparent solubility and surface area Correct answer.
  2. The polymer increases the pH of the dissolution medium
  3. The polymer reacts chemically with the drug to form a soluble salt
  4. The drug is converted into a prodrug

Explanation

In a solid dispersion the drug is dispersed in an inert polymer carrier, often in amorphous or molecular form, which increases apparent solubility and available surface area and thus the dissolution rate. The polymer does not normally alter pH or form a salt.

Question 24Pharmaceutics

A sustained-release tablet is designed using a hydrophilic matrix of hydroxypropyl methylcellulose. Which mechanism primarily controls drug release from this system?

  1. Ion-exchange with gastric acid
  2. Osmotic pumping through a semipermeable membrane
  3. Diffusion of drug through the swollen gel layer combined with erosion of the matrix Correct answer.
  4. Immediate dissolution of the polymer in gastric fluid

Explanation

HPMC hydrates on contact with water to form a viscous gel layer; drug release occurs by diffusion through this gel and by gradual erosion of the matrix. The rate depends on polymer viscosity and concentration.

Question 25Pharmaceutics

A pharmacist needs to calculate the creatinine clearance of a patient using the Cockcroft–Gault equation. Which of the following sets of parameters is required?

  1. Age, height, serum creatinine and blood urea
  2. Age, weight, serum creatinine and sex Correct answer.
  3. Weight, serum creatinine and urine output
  4. Height, weight, body mass index and sex

Explanation

The Cockcroft–Gault equation estimates creatinine clearance from age, body weight, serum creatinine and sex, using the factor (140 − age) × weight / (72 × serum creatinine), with a 0.85 factor for females. Height, BMI and urine output are not part of this equation.

Question 26Pharmaceutics

Which of the following best explains why a tablet is coated with an enteric polymer such as cellulose acetate phthalate?

  1. To provide immediate release of the drug in the stomach
  2. To protect the drug from gastric acid and release it in the intestine Correct answer.
  3. To mask an unpleasant taste during swallowing in the mouth
  4. To increase the mechanical hardness of the tablet core

Explanation

Enteric polymers carry acidic functional groups that remain unionised and insoluble at gastric pH but dissolve as the pH rises in the small intestine. The coating therefore prevents drug release and acid degradation in the stomach and delivers the dose to the intestine. This is the defining purpose of enteric coating.

Question 27Pharmaceutics

A pharmacist prepares 250 mL of a 0.9% w/v sodium chloride solution for irrigation. What mass of sodium chloride is required?

  1. 9.0 g
  2. 2.25 g Correct answer.
  3. 22.5 g
  4. 0.225 g

Explanation

Percentage w/v means grams of solute per 100 mL of solution. A 0.9% w/v solution therefore contains 0.9 g in 100 mL, and for 250 mL the mass is 0.9 × 2.5 = 2.25 g.

Question 28Pharmaceutics

A sterile ophthalmic solution is formulated with benzalkonium chloride as a preservative. Which property of this agent explains why it is generally unsuitable for solutions containing an anionic surfactant or high concentrations of anionic polymers?

  1. It partitions preferentially into the oil phase of an emulsion and is diluted
  2. Its antimicrobial action depends on chelation of divalent metal ions in the formulation
  3. Its cationic quaternary ammonium structure is neutralised by complexation with anionic species Correct answer.
  4. It is inactivated by autoclaving and must be added aseptically after sterilisation

Explanation

Benzalkonium chloride is a cationic surfactant whose positive charge is essential for adsorption onto and disruption of microbial membranes. Anionic surfactants and polymers carry negative charges that form inactive ion pairs or complexes with it, abolishing antimicrobial activity. This is why incompatibility with anionic excipients must be checked when selecting preservatives.

Question 29Pharmaceutics

A drug is to be given as an intravenous bolus and follows a one-compartment model with first-order elimination. Which parameter set is sufficient to predict the plasma concentration at any time after the dose?

  1. Dose, area under the curve and renal clearance
  2. Dose, half-life and fraction unbound in plasma
  3. Dose, clearance and bioavailability
  4. Dose, volume of distribution and elimination rate constant Correct answer.

Explanation

For an intravenous bolus in a one-compartment model, concentration at time t equals (dose/V) multiplied by the exponential of minus k times t. The initial concentration is set by dose and volume of distribution, and the decay by the elimination rate constant. Clearance is derived from V and k, so it adds nothing extra here.

Question 30Pharmaceutics

A suspension of a sparingly soluble drug shows marked caking on storage, with the sediment forming a hard mass that does not redisperse on shaking. Which combination of formulation changes is most appropriate to convert it to a deflocculated-to-flocculated, easily redispersible system?

  1. Increase the proportion of dispersed solid and reduce the concentration of the suspending agent
  2. Add a wetting agent only and store the product at elevated temperature to lower viscosity
  3. Add a controlled amount of electrolyte to induce partial flocculation and include a suspending agent to raise viscosity Correct answer.
  4. Reduce the particle size by prolonged milling and remove all electrolytes from the vehicle

Explanation

Caking arises when deflocculated particles pack tightly and the interparticle repulsion is lost, so the sediment consolidates irreversibly. Controlled flocculation, produced by adding an electrolyte to compress the electrical double layer partially, gives a loose open network that redisperses on shaking. A suspending agent then slows settling and keeps the flocs uniformly distributed.

Question 31Pharmaceutical Chemistry (Inorganic, Organic, Medicinal)

Which official inorganic pharmaceutical preparation is correctly paired with its principal pharmacopoeial use?

  1. Ferrous sulfate - haematinic in iron-deficiency anaemia Correct answer.
  2. Potassium permanganate - intravenous haematinic
  3. Sodium bicarbonate - topical antiseptic
  4. Barium sulfate - systemic antacid

Explanation

Ferrous sulfate supplies divalent iron, which is absorbed and incorporated into haemoglobin, so it is used orally in iron-deficiency anaemia. Barium sulfate is an insoluble radiopaque contrast medium, sodium bicarbonate is a systemic antacid, and potassium permanganate is a topical oxidizing antiseptic, so the other pairings invert their true uses.

Question 32Pharmaceutical Chemistry (Inorganic, Organic, Medicinal)

Which statement correctly describes a limit test used in pharmacopoeial inorganic analysis?

  1. The arsenic limit test depends on reduction of arsenical compounds to arsine gas, which stains mercuric chloride paper Correct answer.
  2. The iron limit test depends on formation of a red thiocyanate complex measured by flame photometry
  3. The chloride limit test depends on oxidation of chloride to chlorine, which bleaches methyl orange
  4. The sulfate limit test depends on precipitation of barium sulfate, which is then weighed gravimetrically

Explanation

In the Gutzeit-type arsenic limit test, nascent hydrogen reduces arsenic to arsine, which reacts with mercuric chloride paper to give a coloured stain compared with a standard. Limit tests are comparative turbidity or colour tests, not gravimetric or flame-photometric assays.

Question 33Pharmaceutical Chemistry (Inorganic, Organic, Medicinal)

A pharmacist needs a sterile, isotonic vehicle for an injection that must not contain sodium ions. Which pharmacopoeial substance is most appropriate?

  1. Sodium citrate
  2. Dextrose Correct answer.
  3. Sodium chloride
  4. Sodium metabisulfite

Explanation

Dextrose (glucose) can be used to render a solution isotonic without contributing sodium ions, which suits sodium-restricted formulations. Sodium chloride, sodium citrate, and sodium metabisulfite all introduce sodium and therefore fail the sodium-free requirement.

Question 34Pharmaceutical Chemistry (Inorganic, Organic, Medicinal)

Which property of bismuth subsalicylate underlies its use in the symptomatic relief of diarrhoea?

  1. It is fully absorbed and acts as a systemic antibiotic
  2. It is largely insoluble and exerts local astringent and antimicrobial actions in the gut lumen Correct answer.
  3. It is a potent systemic anticholinergic
  4. It neutralizes gastric acid by releasing carbon dioxide

Explanation

Bismuth subsalicylate is poorly absorbed and works locally in the gastrointestinal tract, where the bismuth salt has astringent and antimicrobial effects and the salicylate contributes antisecretory activity. It is not a systemic antibiotic, an anticholinergic, or a carbon dioxide-releasing antacid.

Question 35Pharmaceutical Chemistry (Inorganic, Organic, Medicinal)

Which pair of reagents is used in the Lassaigne test to detect nitrogen in an organic compound?

  1. Copper turnings followed by dilute nitric acid
  2. Zinc dust followed by barium chloride
  3. Sodium metal followed by iron(II) sulfate and dilute acid Correct answer.
  4. Potassium iodide followed by starch

Explanation

Lassaigne's test fuses the organic compound with sodium, converting nitrogen to sodium cyanide; addition of iron(II) sulfate and acid then gives Prussian blue ferric ferrocyanide. The other reagent combinations do not generate the cyanide needed for this colour reaction.

Question 36Pharmaceutical Chemistry (Inorganic, Organic, Medicinal)

An organic compound decolorizes bromine water and gives a white precipitate with ammoniacal silver nitrate. Which functional group is most consistent with these observations?

  1. Ketone
  2. Terminal alkyne Correct answer.
  3. Primary alcohol
  4. Aromatic carboxylic acid

Explanation

A terminal alkyne adds bromine across the triple bond, decolorizing bromine water, and its acidic hydrogen forms a silver acetylide precipitate with ammoniacal silver nitrate. Carboxylic acids, alcohols, and ketones do not give the silver acetylide precipitate.

Question 37Pharmaceutical Chemistry (Inorganic, Organic, Medicinal)

Which named reaction is used to convert a carboxylic acid to an amine with one fewer carbon atom?

  1. Cannizzaro reaction
  2. Friedel–Crafts acylation
  3. Claisen condensation
  4. Hofmann rearrangement Correct answer.

Explanation

The Hofmann rearrangement treats a primary amide with bromine and alkali to give an amine containing one carbon fewer than the starting acid. Friedel–Crafts acylation introduces an acyl group onto an aromatic ring, Claisen condensation forms a beta-keto ester, and Cannizzaro disproportionates aldehydes without carbon loss.

Question 38Pharmaceutical Chemistry (Inorganic, Organic, Medicinal)

Which reagent converts an alcohol to an alkyl chloride with inversion of configuration?

  1. Thionyl chloride in pyridine Correct answer.
  2. Sodium dichromate in sulfuric acid
  3. Sodium borohydride
  4. Lithium aluminium hydride

Explanation

Thionyl chloride converts alcohols to alkyl chlorides, and when the reaction proceeds through an SN2 pathway with a suitable substrate it gives inversion of configuration. The hydride reagents reduce carbonyl groups, and acidified dichromate oxidizes alcohols rather than replacing the hydroxyl group.

Question 39Pharmaceutical Chemistry (Inorganic, Organic, Medicinal)

Which statement about aromaticity according to Hückel's rule is correct?

  1. A planar monocyclic system with 4n+2 delocalized pi electrons is aromatic Correct answer.
  2. Any cyclic conjugated system is aromatic regardless of electron count
  3. A planar monocyclic system with 4n delocalized pi electrons is aromatic
  4. A non-planar cyclic system with 4n+2 pi electrons is aromatic

Explanation

Hückel's rule requires a planar, cyclic, fully conjugated system containing 4n+2 pi electrons, such as benzene with six. Systems with 4n pi electrons are antiaromatic if planar and conjugated, and non-planar systems cannot sustain the required cyclic delocalization.

Question 40Pharmaceutical Chemistry (Inorganic, Organic, Medicinal)

Which factor most increases the rate of an SN1 reaction of an alkyl halide?

  1. Formation of a tertiary carbocation intermediate Correct answer.
  2. A protic solvent that poorly solvates carbocations
  3. A primary carbon bearing the leaving group
  4. A strong nucleophile in high concentration

Explanation

The SN1 mechanism proceeds through a carbocation, and tertiary carbocations are stabilized by hyperconjugation, lowering the activation energy. Strong nucleophile concentration mainly affects SN2, primary carbons disfavour carbocation formation, and poor carbocation solvation slows the reaction.

Question 41Pharmaceutical Chemistry (Inorganic, Organic, Medicinal)

In a medicinal chemistry context, which structural change most commonly reduces the lipophilicity of a lead compound?

  1. Introduction of a methyl group
  2. Introduction of a carboxylic acid group Correct answer.
  3. Introduction of a trifluoromethyl group
  4. Introduction of a phenyl ring

Explanation

Ionizable acidic groups such as carboxylic acids lower the partition coefficient by increasing aqueous solubility and ionization at physiological pH. Methyl, trifluoromethyl, and phenyl substituents are lipophilic and generally raise log P.

Question 42Pharmaceutical Chemistry (Inorganic, Organic, Medicinal)

Which principle underlies the use of a prodrug in medicinal chemistry?

  1. The prodrug is converted in vivo to the active species, improving delivery or pharmacokinetic behaviour Correct answer.
  2. The prodrug is designed to avoid all metabolic transformation
  3. The prodrug is a racemic mixture of two active enantiomers
  4. The prodrug binds irreversibly to its receptor to prolong action

Explanation

A prodrug is a pharmacologically inactive derivative that undergoes biotransformation to release the active drug, often improving absorption, stability, or targeting. It is not defined by irreversible binding, metabolic inertness, or racemic composition.

Question 43Pharmaceutical Chemistry (Inorganic, Organic, Medicinal)

Which physicochemical property is best predicted by Lipinski's rule of five for a compound intended for oral absorption?

  1. Enhanced oral absorption when hydrogen-bond donors exceed 10
  2. Poor oral absorption when there are fewer than 5 rotatable bonds
  3. Enhanced oral absorption when log P exceeds 5
  4. Poor oral absorption when molecular weight exceeds 500 Da Correct answer.

Explanation

Lipinski's rule flags likely poor absorption when molecular weight exceeds 500 Da, log P exceeds 5, hydrogen-bond donors exceed 5, or acceptors exceed 10. The other options invert these thresholds or introduce a criterion that is not part of the rule.

Question 44Pharmaceutical Chemistry (Inorganic, Organic, Medicinal)

Which bioisosteric replacement of a carboxylic acid group is commonly used to retain acidity while improving metabolic stability?

  1. Tetrazole Correct answer.
  2. Methyl ester
  3. Primary amide
  4. Tertiary butyl group

Explanation

A tetrazole ring is an acidic bioisostere of the carboxylic acid group, with a comparable pKa, and it resists the metabolic conjugation that affects carboxylates. Methyl esters and amides are not acidic, and a tert-butyl group is lipophilic and non-ionizable.

Question 45Pharmaceutical Chemistry (Inorganic, Organic, Medicinal)

Which stereochemical relationship exists between a pair of enantiomers?

  1. They are non-superimposable mirror images with identical physical properties in achiral environments Correct answer.
  2. They are diastereomers that differ at only one stereocentre
  3. They are superimposable mirror images with opposite melting points
  4. They are constitutional isomers with different functional groups

Explanation

Enantiomers are non-superimposable mirror images and have identical physical properties except for the direction of rotation of plane-polarized light in achiral media. Superimposable mirror images describe the same molecule, constitutional isomers differ in connectivity, and diastereomers are not mirror images.

Question 46Pharmaceutical Chemistry (Inorganic, Organic, Medicinal)

A drug contains one chiral centre and is administered as the racemate. Which consequence follows directly from this?

  1. The two enantiomers may differ in pharmacodynamics and pharmacokinetics Correct answer.
  2. The two enantiomers must have identical receptor affinities
  3. The enantiomers interconvert spontaneously at physiological pH
  4. The racemate must be pharmacologically inactive

Explanation

Because biological receptors are chiral, enantiomers can differ in binding affinity, intrinsic activity, and disposition such as metabolism and protein binding. Identical receptor affinity, inactivity of the racemate, and spontaneous interconversion are not general consequences of racemic administration.

Question 47Pharmaceutical Chemistry (Inorganic, Organic, Medicinal)

Which analytical method is most appropriate for determining the absolute configuration and conformation of a small organic drug molecule in solution?

  1. Nuclear magnetic resonance spectroscopy with chiral shift reagents and NOE experiments Correct answer.
  2. Flame photometry
  3. Conductometry
  4. Atomic absorption spectroscopy

Explanation

NMR spectroscopy provides stereochemical information through nuclear Overhauser effects and coupling constants, and chiral shift reagents or chiral solvating agents can resolve enantiomeric signals. Atomic absorption, flame photometry, and conductometry measure elemental content or ionic conductivity and give no three-dimensional structural detail.

Question 48Pharmaceutical Chemistry (Inorganic, Organic, Medicinal)

Which reagent is used in the bromometric assay of phenol-type compounds in pharmacopoeial titrimetry?

  1. Ceric ammonium sulfate with ferroin indicator
  2. Potassium bromate with potassium bromide in acidic medium Correct answer.
  3. Silver nitrate with potassium chromate
  4. Sodium thiosulfate with starch indicator

Explanation

Bromometric titration generates bromine in situ from bromate and bromide in acid, and the bromine substitutes into the activated aromatic ring of phenols. Thiosulfate is the titrant used to determine excess bromine, while silver nitrate and ceric sulfate serve other assay types.

Question 49Pharmaceutical Chemistry (Inorganic, Organic, Medicinal)

Which observation indicates that a sample of sodium chloride contains an unacceptable level of iodide in a limit test?

  1. Liberation of iodine, detected as a blue colour with starch mucilage Correct answer.
  2. Effervescence with dilute hydrochloric acid
  3. Formation of a white precipitate with barium chloride
  4. A yellow flame in the flame test

Explanation

In the iodide limit test, iodide is oxidized to iodine, which gives a blue colour with starch mucilage that is compared with a standard. Barium chloride tests for sulfate, acid effervescence indicates carbonate, and a yellow flame indicates sodium itself.

Question 50Pharmaceutical Chemistry (Inorganic, Organic, Medicinal)

Which statement about the redox titration of hydrogen peroxide with potassium permanganate in dilute sulfuric acid is correct?

  1. Permanganate is reduced to manganese(II) and the end point is a persistent pale pink colour Correct answer.
  2. Permanganate is oxidized to manganese dioxide and the end point is a brown precipitate
  3. The titration must be performed in alkaline medium for a sharp end point
  4. Hydrogen peroxide acts as the oxidizing agent and permanganate as the reducing agent

Explanation

In acid, permanganate is reduced from manganese(VII) to manganese(II), while hydrogen peroxide is oxidized to oxygen, and the first permanent pink colour marks the end point. Manganese dioxide forms in neutral or alkaline conditions, and the roles of oxidant and reductant are the reverse of those stated in the third option.