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Cambodia Pharmacy Exit Exam study materials
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Cambodia Pharmacy Exit Exam practice questions

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Question 1Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

A pharmacist prepares a 500 mL batch of oral rehydration solution containing 1.5 g of sodium chloride. What is the percentage strength (w/v) of sodium chloride in the batch?

  1. 0.15% w/v
  2. 1.5% w/v
  3. 3.0% w/v
  4. 0.3% w/v Correct answer.

Explanation

Percentage weight-in-volume is calculated as grams of solute per 100 mL of solution. Here 1.5 g in 500 mL equals 0.3 g per 100 mL, which is 0.3% w/v.

Question 2Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

Which dosage form is designed to release drug after a lag time and is typically coated with an enteric polymer that dissolves above pH 5.5?

  1. Sublingual tablet
  2. Effervescent tablet
  3. Immediate-release tablet
  4. Enteric-coated tablet Correct answer.

Explanation

Enteric coatings such as cellulose acetate phthalate resist gastric acid and dissolve in the higher pH of the intestine, protecting the drug or the stomach. This produces a delayed release rather than immediate release.

Question 3Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

During wet granulation, which excipient is added primarily to promote adhesion of powder particles into granules?

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

Explanation

A binder such as povidone or starch paste increases particle cohesion during granulation and gives the granule its strength. It is distinct from disintegrants, which later break the tablet apart.

Question 4Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

A pharmacist must compound a sterile ophthalmic solution but the pharmacy has no autoclave. Which method is appropriate for terminal sterilization of a heat-labile solution in its final sealed container?

  1. Boiling in a water bath for 30 minutes
  2. Dry heat sterilization at 160 degrees Celsius
  3. Moist heat sterilization at 121 degrees Celsius
  4. Filtration through a 0.22 micron membrane Correct answer.

Explanation

Filtration through a 0.22 micron membrane removes bacteria from heat-labile solutions without exposing the drug to thermal degradation. The filtered solution is then filled aseptically into sterile containers.

Question 5Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

Which statement correctly describes the purpose of the accelerated stability study condition of 40 degrees Celsius and 75% relative humidity?

  1. It replaces the need for real-time stability testing.
  2. It measures microbial contamination of the product.
  3. It predicts long-term shelf life from short-term degradation data. Correct answer.
  4. It is the mandatory storage condition for all finished products.

Explanation

Accelerated conditions stress the product so that degradation kinetics can be extrapolated to estimate shelf life in a shorter time. Real-time data at the intended storage condition are still required to confirm the prediction.

Question 6Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

A tablet formulation contains lactose, microcrystalline cellulose, magnesium stearate and talc. Which ingredient functions as the lubricant?

  1. Talc
  2. Microcrystalline cellulose
  3. Magnesium stearate Correct answer.
  4. Lactose

Explanation

Magnesium stearate is the standard tablet lubricant; it reduces friction between the tablet and the die wall during ejection. Talc can act as a glidant, and lactose and microcrystalline cellulose are diluents.

Question 7Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

Which of the following is a primary packaging component for a sterile injection?

  1. The shipping corrugated box
  2. The patient information leaflet
  3. The printed carton
  4. The glass vial and rubber stopper Correct answer.

Explanation

Primary packaging is in direct contact with the product and provides the critical barrier, here the glass vial and the elastomeric closure. Cartons, leaflets and shipping boxes are secondary or tertiary packaging.

Question 8Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

A suspension is formulated with a flocculating agent. Which property is expected compared with a deflocculated suspension?

  1. Irreversible caking on standing
  2. A clear transparent appearance
  3. No sedimentation at all
  4. Faster sedimentation with easy redispersion Correct answer.

Explanation

Flocculated suspensions form loose aggregates that settle quickly but redisperse readily on shaking. Deflocculated systems settle slowly but tend to form a hard cake that cannot be redispersed.

Question 9Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

A drug follows first-order degradation with a rate constant of 0.05 per month at 25 degrees Celsius. Approximately what is its half-life at this temperature?

  1. 7 months
  2. 20 months
  3. 14 months Correct answer.
  4. 35 months

Explanation

For first-order kinetics the half-life equals 0.693 divided by the rate constant. Dividing 0.693 by 0.05 per month gives about 13.9 months, which rounds to 14 months.

Question 10Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

Which manufacturing defect in a compressed tablet appears as separation of the tablet top from the main body, often caused by entrapped air?

  1. Sticking
  2. Capping Correct answer.
  3. Picking
  4. Mottling

Explanation

Capping is the partial or complete separation of the upper crown of a tablet and is commonly caused by air entrapment or excessive compression speed. It differs from lamination, which is horizontal splitting within the tablet body.

Question 11Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

A pharmacist needs to prepare 200 g of a 5% w/w hydrocortisone ointment using a 20% w/w stock ointment and white petrolatum. How much stock ointment is required?

  1. 10 g
  2. 40 g
  3. 20 g
  4. 50 g Correct answer.

Explanation

The alligation method shows that 5 parts of 20% stock must be diluted with 15 parts of base to yield 20 parts of a 5% product. Scaling to 200 g, the stock is 5/20 of 200 g, which is 50 g.

Question 12Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

Which quality test is specifically required for a sterile ophthalmic ointment but not for a non-sterile topical ointment?

  1. Uniformity of content
  2. Sterility testing Correct answer.
  3. Metal particle detection
  4. Weight variation

Explanation

Ophthalmic products must be sterile because the eye is a sensitive, immune-privileged site vulnerable to infection. Non-sterile topical ointments are not subject to a sterility requirement.

Question 13Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

A tablet is manufactured by direct compression. Which property of the powder blend most directly determines whether the blend will fill the die uniformly and produce consistent tablet weight?

  1. Disintegration time
  2. Friability
  3. Angle of repose Correct answer.
  4. Hardness

Explanation

The angle of repose measures flowability; a low angle indicates good flow that fills the die evenly and gives consistent weight. Poor flow causes weight variation and content non-uniformity.

Question 14Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

In aseptic processing, which practice best reduces the risk of microbial contamination of a product that cannot be terminally sterilized?

  1. Filtering the product through a 0.45 micron filter
  2. Performing filling inside a Grade A laminar airflow zone within a Grade B cleanroom Correct answer.
  3. Increasing the concentration of preservative in the formulation
  4. Testing the final product for sterility before release

Explanation

Aseptic filling requires a Grade A unidirectional airflow zone surrounded by a Grade B environment to keep airborne contamination away from the exposed product. Environmental monitoring and operator technique support this barrier.

Question 15Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

A drug in solution degrades by hydrolysis. Which formulation strategy most effectively slows this degradation in an aqueous injection?

  1. Storing the product at a higher temperature
  2. Adding a chelating agent such as EDTA
  3. Adjusting the pH to the drug's pH of maximum stability Correct answer.
  4. Increasing the ionic strength of the vehicle

Explanation

Hydrolysis rates are strongly pH-dependent, so formulating at the pH of maximum stability minimizes degradation. Chelating agents address metal-catalyzed oxidation, not hydrolysis.

Question 16Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

Which piece of equipment is used to assess the mechanical strength of a tablet by measuring the force required to crush it?

  1. Dissolution apparatus
  2. Disintegration tester
  3. Friabilator
  4. Hardness tester Correct answer.

Explanation

A hardness tester applies a diametral crushing force and reports the tablet's breaking force in newtons or kiloponds. Friability, disintegration and dissolution measure different quality attributes.

Question 17Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

A pharmacy prepares a suppository base from theobroma oil. Which property of theobroma oil requires careful control of the compounding temperature?

  1. It has a high melting point above 70 degrees Celsius.
  2. It is water-soluble and dissolves rapidly at room temperature.
  3. It is a glyceride that melts near body temperature but is polymorphic and can solidify in unstable forms if overheated. Correct answer.
  4. It is a mineral oil that does not solidify on cooling.

Explanation

Theobroma oil melts around 34 to 36 degrees Celsius but exists in several polymorphic forms; overheating above about 36 degrees Celsius can produce a lower-melting form that fails to set properly. Gentle melting and controlled cooling preserve the stable beta form.

Question 18Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

Which statement about the biopharmaceutics classification of a drug with high solubility and low permeability is correct?

  1. It belongs to BCS Class I, and both dissolution and absorption are rapid.
  2. It belongs to BCS Class III, and dissolution is rapid but absorption is limited by permeability. Correct answer.
  3. It belongs to BCS Class IV, and both solubility and permeability are poor.
  4. It belongs to BCS Class II, and dissolution is the rate-limiting step.

Explanation

BCS Class III drugs dissolve readily but permeate the intestinal membrane poorly, so permeability limits oral absorption. For such drugs, dissolution testing is less predictive of bioavailability.

Question 19Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

A tablet blend contains a hygroscopic drug. Which excipient choice is most appropriate to protect the product from moisture during storage?

  1. Anhydrous lactose as the diluent Correct answer.
  2. A film coat containing a water-soluble polymer without a moisture barrier
  3. An effervescent couple
  4. A hygroscopic binder such as povidone in high proportion

Explanation

Anhydrous lactose is a non-hygroscopic diluent that does not attract moisture and is compatible with moisture-sensitive drugs. Avoiding hygroscopic excipients and adding a moisture-barrier coat further protects the product.

Question 20Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

Which is the correct interpretation of a dissolution profile in which 85% of drug is released within 30 minutes in 0.1 N hydrochloric acid?

  1. The product fails the dissolution specification.
  2. The product is a delayed-release dosage form.
  3. The product is a sustained-release dosage form.
  4. The product is likely to behave as an immediate-release dosage form. Correct answer.

Explanation

Rapid release of most of the dose in gastric fluid is characteristic of immediate-release products. Delayed-release products would resist acid and release drug only at intestinal pH.

Question 21Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

A manufacturer wants to reduce the risk of cross-contamination between two potent products made on the same line. Which control is most directly effective?

  1. Reducing the number of quality control tests
  2. Increasing the batch size of each product
  3. Storing both products in the same warehouse
  4. Validated cleaning procedures with residue limits and dedicated equipment where necessary Correct answer.

Explanation

Validated cleaning procedures with scientifically justified residue limits remove active ingredient between campaigns, and dedicated equipment is used for highly potent or sensitizing products. This directly addresses cross-contamination risk.

Question 22Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

A suspension is stabilized with a polymer that adsorbs onto particle surfaces. Which mechanism explains the improved stability?

  1. Reduction of the zeta potential to zero
  2. Increase in particle size by agglomeration
  3. Steric stabilization that prevents particles from approaching closely enough to aggregate Correct answer.
  4. Removal of all water from the system

Explanation

Adsorbed polymer chains create a steric barrier that opposes close approach of particles and prevents aggregation. This is especially useful in non-aqueous or high-electrolyte systems where electrostatic repulsion is weak.

Question 23Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

During validation of a moist heat sterilization cycle, a biological indicator with a D-value of 1.5 minutes at 121 degrees Celsius is used. To achieve a 12-log reduction, what is the minimum exposure time at 121 degrees Celsius?

  1. 18 minutes Correct answer.
  2. 15 minutes
  3. 24 minutes
  4. 12 minutes

Explanation

The required exposure equals the D-value multiplied by the number of log reductions. Multiplying 1.5 minutes by 12 gives 18 minutes at 121 degrees Celsius.

Question 24Pharmaceutics and Pharmaceutical Technology (dosage forms, compounding, stability, manufacturing quality)

A formulation scientist observes that a drug's degradation rate doubles when the temperature is raised by 10 degrees Celsius. Using the Arrhenius relationship, which conclusion is most defensible?

  1. A Q10 of about 2 indicates that degradation is zero-order.
  2. A Q10 of about 2 indicates that a 20 degree Celsius rise will increase the rate roughly fourfold. Correct answer.
  3. A Q10 of about 2 indicates that shelf life is independent of temperature.
  4. A Q10 of about 2 indicates that the reaction is unaffected by pH.

Explanation

Q10 is the factor by which reaction rate increases for each 10 degree Celsius rise. With Q10 near 2, two successive 10 degree increments multiply the rate by about four, which shortens shelf life accordingly.

Question 25Pharmaceutical Chemistry and Drug Analysis (medicinal chemistry, quality control, instrumentation)

A pharmacist performs a thin-layer chromatographic identity test on a paracetamol tablet. Which statement best describes the role of the stationary phase in this separation?

  1. It provides a surface on which components partition between a liquid stationary layer and the mobile phase
  2. It reacts chemically with the analyte to produce a coloured derivative for detection
  3. It acts as a solvent reservoir that continuously feeds the mobile phase up the plate
  4. It selectively retains analytes by adsorption according to their polarity and functional groups Correct answer.

Explanation

In normal-phase TLC on silica gel, the solid adsorbent retains analytes by adsorption, and the strength of retention depends on analyte polarity and the functional groups available for hydrogen bonding or dipole interaction. The mobile phase carries the sample and competes for these adsorption sites, so more polar analytes move more slowly. This adsorption mechanism is what gives TLC its selectivity for identity testing.

Question 26Pharmaceutical Chemistry and Drug Analysis (medicinal chemistry, quality control, instrumentation)

A quality-control analyst measures the absorbance of a drug solution at 257 nm in a 1 cm cell and obtains A = 0.482. The molar absorptivity of the drug at this wavelength is 1.24 x 10^4 L mol^-1 cm^-1. What is the molar concentration of the solution?

  1. 2.57 x 10^-4 mol/L
  2. 1.24 x 10^-4 mol/L
  3. 5.98 x 10^-3 mol/L
  4. 3.89 x 10^-5 mol/L Correct answer.

Explanation

Beer-Lambert law states A = epsilon x b x c, so c = A / (epsilon x b). Substituting gives 0.482 / (1.24 x 10^4 x 1) = 3.89 x 10^-5 mol/L. The result is a small molarity, consistent with a strongly absorbing chromophore at a low concentration.

Question 27Pharmaceutical Chemistry and Drug Analysis (medicinal chemistry, quality control, instrumentation)

During assay of a weak acid by non-aqueous titration, the sample is dissolved in anhydrous acetic acid and titrated with perchloric acid. What is the principal reason acetic acid is chosen as the solvent?

  1. It reacts with perchloric acid to generate a stronger titrant in situ
  2. It buffers the solution so the endpoint colour is sharper
  3. It suppresses ionisation of the drug so the titration behaves as a precipitation reaction
  4. It dissolves the drug and enhances the basicity of the analyte so it can be titrated as a base Correct answer.

Explanation

Acetic acid is a protogenic solvent that donates protons to weak bases and thereby enhances their basicity, making weak bases titratable with perchloric acid in a single sharp step. Perchloric acid in acetic acid is a very strong acid because the solvent levels the acid strength. This is the basis of non-aqueous titration of weak bases and their salts.

Question 28Pharmaceutical Chemistry and Drug Analysis (medicinal chemistry, quality control, instrumentation)

Which functional group is primarily responsible for the characteristic strong carbonyl stretching absorption of a ketone near 1715 cm^-1 in the infrared spectrum?

  1. N-H bend of a primary amine
  2. C=O double bond of the carbonyl Correct answer.
  3. C=C double bond of an alkene
  4. C-O single bond of an alcohol

Explanation

Infrared absorption arises when a bond vibration produces a change in dipole moment. The C=O stretch of a ketone is strong and appears near 1715 cm^-1 because the polar carbonyl bond changes dipole moment substantially during stretching. Conjugation and hydrogen bonding shift this band, which is useful for structure confirmation.

Question 29Pharmaceutical Chemistry and Drug Analysis (medicinal chemistry, quality control, instrumentation)

A validated HPLC assay for a tablet requires the system suitability criterion that the relative standard deviation of six replicate injections of the standard be no more than 2.0 percent. Six injections give peak areas of 1002, 998, 1005, 995, 1000 and 1000 (arbitrary units). What is the sample standard deviation, and does the system pass?

  1. About 0.3 units, so the system passes the criterion
  2. About 3.3 units, so the system fails the criterion
  3. About 3.3 units, so the system passes the criterion Correct answer.
  4. About 12 units, so the system fails the criterion

Explanation

The mean is 1000 and the deviations are 2, -2, 5, -5, 0 and 0, giving a sum of squares of 58. Dividing by n-1 = 5 gives a variance of 11.6, so the sample standard deviation is about 3.4 units, which is about 0.34 percent RSD. This is well below the 2.0 percent limit, so the system suitability criterion is met.

Question 30Pharmaceutical Chemistry and Drug Analysis (medicinal chemistry, quality control, instrumentation)

Which pharmacopoeial test is designed specifically to detect the presence of free salicylic acid as a degradation product in aspirin?

  1. Determination of pH of a 1 percent suspension
  2. Limit test for related substances by colour reaction with iron(III) chloride Correct answer.
  3. Sulphated ash determination
  4. Loss on drying

Explanation

Salicylic acid reacts with iron(III) chloride to give a violet complex, and this colour reaction is used as a limit test for free salicylic acid in aspirin. Aspirin hydrolyses to salicylic acid and acetic acid, so this test monitors a key degradation pathway. The intensity of the colour is compared with a standard to set the limit.

Question 31Pharmaceutical Chemistry and Drug Analysis (medicinal chemistry, quality control, instrumentation)

In proton nuclear magnetic resonance spectroscopy, what information does the integration (area) of a signal provide?

  1. The number of neighbouring protons that split the signal
  2. The number of chemically equivalent protons giving rise to that signal Correct answer.
  3. The rate of exchange of the proton with the solvent
  4. The electronic environment of the proton expressed as a chemical shift

Explanation

The area under an NMR signal is proportional to the number of equivalent protons resonating at that frequency, so integration gives the relative proton count for each environment. This complements chemical shift, which reports the electronic environment, and splitting, which reports neighbouring protons. Together these allow structural assignment.

Question 32Pharmaceutical Chemistry and Drug Analysis (medicinal chemistry, quality control, instrumentation)

Which statement correctly describes the relationship between the absorbance measured in a spectrophotometric assay and the concentration of the absorbing species?

  1. Absorbance is proportional to the logarithm of concentration at all concentrations
  2. Absorbance is independent of path length when the cell is quartz
  3. Absorbance increases linearly with concentration only at very high concentrations
  4. Absorbance is directly proportional to concentration and path length at a fixed wavelength Correct answer.

Explanation

The Beer-Lambert law states that absorbance equals the product of molar absorptivity, path length and concentration at a given wavelength. Within the linear range, doubling the concentration or the path length doubles the absorbance. Deviations occur at high concentration or with stray light, which is why assays are validated within a defined range.

Question 33Pharmaceutical Chemistry and Drug Analysis (medicinal chemistry, quality control, instrumentation)

A tablet contains a drug that is a weak base with a pKa of 8.4. In which pH range would the drug exist predominantly in its unionised form, favouring passive absorption across lipid membranes?

  1. pH 7.4
  2. pH 6.4
  3. pH 10.4 Correct answer.
  4. pH 5.4

Explanation

For a weak base, the protonated (ionised) form predominates when pH is below the pKa, and the un-ionised form predominates when pH is above the pKa. At pH 10.4, two units above the pKa, the ratio of un-ionised to ionised species is about 100:1, so the drug is largely unionised. Unionised species are more lipid-soluble and permeate membranes more readily.

Question 34Pharmaceutical Chemistry and Drug Analysis (medicinal chemistry, quality control, instrumentation)

Which analytical technique is best suited to confirm the identity of a drug substance by comparing its mass spectrum and fragmentation pattern with a reference standard?

  1. Refractometry
  2. Gas chromatography coupled with mass spectrometry Correct answer.
  3. Polarimetry
  4. Flame photometry

Explanation

Mass spectrometry provides the molecular ion mass and a reproducible fragmentation pattern that is highly characteristic of a compound, and coupling with gas chromatography adds a retention-time dimension. Matching both the mass spectrum and retention time against a reference standard gives strong identity confirmation. The other techniques measure bulk physical properties and are far less specific.

Question 35Pharmaceutical Chemistry and Drug Analysis (medicinal chemistry, quality control, instrumentation)

In a complexometric titration of a metal ion with disodium edetate, what is the function of the indicator such as murexide or eriochrome black T?

  1. It oxidises the metal ion so that it reacts more rapidly with edetate
  2. It precipitates the metal ion before the endpoint is reached
  3. It buffers the solution at a constant pH throughout the titration
  4. It forms a coloured complex with the metal ion that changes colour when the metal is sequestered by the titrant Correct answer.

Explanation

Metal-ion indicators form a coloured complex with the analyte metal that is weaker than the metal-edetate complex. As edetate is added, it competes for the metal; at the endpoint the indicator is displaced and its free colour appears. This colour change signals the equivalence point.

Question 36Pharmaceutical Chemistry and Drug Analysis (medicinal chemistry, quality control, instrumentation)

Which structural feature of the sulfonamide antibacterial class is essential for its antibacterial activity?

  1. A free aromatic amino group para to the sulfonamide group Correct answer.
  2. An unsubstituted sulfonamide nitrogen that can be replaced by any alkyl chain
  3. A carboxylic acid group on the aromatic ring
  4. A quaternary ammonium centre adjacent to the sulfur atom

Explanation

Sulfonamides act as antimetabolites of para-aminobenzoic acid in bacterial folate synthesis, and the para-amino group on the benzene ring is required for this mimicry. The sulfonamide group itself is also essential, but the free para-amino group is the key structural feature for activity. Modifications to these groups reduce or abolish antibacterial action.

Question 37Pharmaceutical Chemistry and Drug Analysis (medicinal chemistry, quality control, instrumentation)

Which statement best explains why a drug molecule that is a prodrug requires metabolic conversion before it can exert its pharmacological effect?

  1. The prodrug is converted only by non-enzymatic hydrolysis in the stomach
  2. The prodrug is designed to be inactive until enzymes release or form the active species Correct answer.
  3. The prodrug has a higher receptor affinity than the active drug
  4. The prodrug is always more water-soluble than the active drug

Explanation

A prodrug is a pharmacologically inactive derivative that undergoes enzymatic or chemical transformation in the body to release the active drug. This design is used to improve absorption, stability or taste, or to target activation to a specific tissue. The active species, not the prodrug, binds the receptor.

Question 38Pharmaceutical Chemistry and Drug Analysis (medicinal chemistry, quality control, instrumentation)

A pharmacist observes that a batch of amoxicillin capsules has a moisture content above the specification limit. Which degradation pathway is most likely accelerated by this finding?

  1. Photochemical decomposition caused by ultraviolet light
  2. Racemisation of the phenylglycine side chain
  3. Hydrolytic cleavage of the beta-lactam ring Correct answer.
  4. Oxidation of the thiazolidine sulfur

Explanation

The beta-lactam ring of penicillins is strained and susceptible to hydrolysis, and moisture provides the water and mobility needed for this reaction. Hydrolysis opens the ring to form penicilloic acid, which is inactive and can cause allergic reactions. This is why amoxicillin products are packaged with desiccants and stored dry.

Question 39Pharmaceutical Chemistry and Drug Analysis (medicinal chemistry, quality control, instrumentation)

Which pharmacopoeial test is used to determine the uniformity of content of a low-dose tablet formulation?

  1. Uniformity of content Correct answer.
  2. Disintegration testing
  3. Uniformity of mass
  4. Friability testing

Explanation

Uniformity of content measures the amount of active substance in individual dosage units and is applied when the drug content is low or the drug is unevenly distributed. It is distinct from uniformity of mass, which simply checks weight variation. Content uniformity ensures each tablet delivers the labelled dose.

Question 40Pharmaceutical Chemistry and Drug Analysis (medicinal chemistry, quality control, instrumentation)

A UV spectrophotometric assay of a drug is performed at 254 nm. The analyst notices that the calibration curve deviates from linearity at the highest concentrations tested. Which explanation best accounts for this observation?

  1. The cell path length changes with concentration
  2. The solvent absorbs more strongly at high concentration
  3. The molar absorptivity changes because the wavelength is altered
  4. Stray light and solute-solute interactions reduce the effective absorbance at high concentration Correct answer.

Explanation

Deviations from the Beer-Lambert law at high concentration arise from stray light, which becomes a larger fraction of the transmitted light, and from solute-solute interactions that alter absorptivity. These effects make the calibration curve flatten at the upper end. Validated assays therefore specify a working concentration range where linearity holds.

Question 41Pharmaceutical Chemistry and Drug Analysis (medicinal chemistry, quality control, instrumentation)

Which statement correctly describes the role of the mobile phase in reversed-phase high-performance liquid chromatography?

  1. It is a non-polar solvent that competes with the stationary phase for non-polar analytes
  2. It is a solid adsorbent that retains analytes by adsorption
  3. It is an ionisable gas that carries vaporised analytes through the column
  4. It is a polar solvent mixture that elutes analytes from a non-polar stationary phase Correct answer.

Explanation

In reversed-phase HPLC the stationary phase is non-polar, such as a C18 bonded silica, and the mobile phase is a polar mixture of water with an organic modifier like methanol or acetonitrile. More polar analytes partition into the mobile phase and elute earlier, while non-polar analytes are retained longer. Changing the organic proportion adjusts retention.

Question 42Pharmaceutical Chemistry and Drug Analysis (medicinal chemistry, quality control, instrumentation)

In the context of pharmaceutical quality control, what does the term 'specificity' of an analytical method describe?

  1. The ability of the method to remain unaffected by small deliberate changes in operating parameters
  2. The ability of the method to produce the same result on repeated occasions
  3. The ability of the method to measure the analyte accurately in the presence of impurities, degradants and excipients Correct answer.
  4. The closeness of agreement between the measured value and the true value

Explanation

Specificity is the ability of a method to assess unequivocally the analyte of interest in the presence of components that may be expected to be present, such as impurities, degradants and excipients. It confirms that the measured signal truly comes from the analyte. It is distinct from accuracy, precision and robustness.

Question 43Pharmaceutical Chemistry and Drug Analysis (medicinal chemistry, quality control, instrumentation)

A candidate structure contains a carboxylic acid group with a pKa of about 4.5. In the small intestine at pH 6.5, which form of the carboxylic acid predominates and what is the approximate ratio of ionised to unionised species?

  1. Ionised form, with a ratio of about 1:1
  2. Ionised form, with a ratio of about 100:1 Correct answer.
  3. Unionised form, with a ratio of about 10:1
  4. Unionised form, with a ratio of about 1:100

Explanation

For a weak acid, the ionised carboxylate form predominates when pH is above the pKa. The difference is 6.5 - 4.5 = 2 pH units, and each unit corresponds to a tenfold change in the ratio, so the ionised to unionised ratio is about 100:1. This extensive ionisation limits passive absorption of the acid in the intestine.

Question 44Pharmaceutical Chemistry and Drug Analysis (medicinal chemistry, quality control, instrumentation)

Which analytical method is most appropriate for quantifying a drug that lacks a strong chromophore and cannot be detected by UV absorbance?

  1. Direct UV spectrophotometry at 254 nm
  2. Titration with sodium hydroxide
  3. Refractive index detection after HPLC separation Correct answer.
  4. Flame emission spectrophotometry

Explanation

Refractive index detection responds to any change in refractive index caused by the analyte and does not require a chromophore, making it suitable for compounds with no UV-absorbing group. It is used in HPLC for sugars, lipids and other non-chromophoric substances. Its lower sensitivity compared with UV detection is a recognised limitation.

Question 45Pharmacognosy and Natural Products (medicinal plants, phytochemistry, traditional medicine)

Which alkaloid is the principal bioactive constituent of the opium poppy (Papaver somniferum) used as the reference standard for assay of raw opium?

  1. Morphine Correct answer.
  2. Atropine
  3. Reserpine
  4. Quinine

Explanation

Morphine is the major benzylisoquinoline-derived alkaloid of opium and serves as the pharmacopoeial marker for assay of raw opium. Quinine comes from Cinchona bark, atropine from Atropa belladonna, and reserpine from Rauwolfia serpentina, so none of these is the opium reference alkaloid.

Question 46Pharmacognosy and Natural Products (medicinal plants, phytochemistry, traditional medicine)

A dried leaf drug is required to contain not less than 1% volatile oil composed mainly of menthol. Which plant material does this pharmacognostic specification describe?

  1. Eucalyptus globulus
  2. Cinnamomum cassia
  3. Ocimum sanctum
  4. Mentha piperita Correct answer.

Explanation

Peppermint leaf (Mentha piperita) is standardized on its volatile oil, which is rich in menthol and menthone. Ocimum sanctum oil is dominated by eugenol, eucalyptus oil by 1,8-cineole, and cassia bark oil by cinnamaldehyde, so their marker constituents differ.

Question 47Pharmacognosy and Natural Products (medicinal plants, phytochemistry, traditional medicine)

Sennosides A and B, the purgative principles of senna, belong to which phytochemical class?

  1. Cardiac glycosides
  2. Anthraquinone glycosides Correct answer.
  3. Saponin glycosides
  4. Cyanogenic glycosides

Explanation

Sennosides are dianthrone O-glycosides based on anthraquinone-type aglycones, which act on the colon after bacterial hydrolysis. Cardiac glycosides such as digoxin act on the heart, cyanogenic glycosides release hydrogen cyanide, and saponins are surface-active triterpenoid or steroid glycosides, so none matches the laxative action.

Question 48Pharmacognosy and Natural Products (medicinal plants, phytochemistry, traditional medicine)

Which pharmacognostic test is used to detect the presence of starch grains in a powdered crude drug under the microscope?

  1. Ferric chloride giving a blue-green coloration
  2. Iodine solution giving a blue-black coloration Correct answer.
  3. Liebermann-Burchard reagent giving a red coloration
  4. Dragendorff reagent giving an orange precipitate

Explanation

Starch grains stain blue-black with iodine because of the amylose-iodine complex, which is a standard histochemical test for starch in powdered drugs. Ferric chloride detects tannins, Dragendorff reagent detects alkaloids, and Liebermann-Burchard detects sterols and triterpenes.

Question 49Pharmacognosy and Natural Products (medicinal plants, phytochemistry, traditional medicine)

A crude drug extract is shaken with water and produces a persistent froth that is not dispelled by adding dilute acid. This behaviour is most characteristic of which constituent?

  1. Fixed oils
  2. Tannins
  3. Saponins Correct answer.
  4. Alkaloids

Explanation

Saponins lower surface tension and form a stable, persistent froth when shaken with water; acid addition does not abolish the foam, unlike carbonate-derived effervescence. Tannins precipitate proteins, alkaloids are detected by precipitation reagents, and fixed oils form a separate oily layer rather than a stable foam.

Question 50Pharmacognosy and Natural Products (medicinal plants, phytochemistry, traditional medicine)

Freshly prepared Aloe latex is examined for its characteristic anthraquinone derivative. Which compound is used as the marker for aloe in pharmacopoeial identity tests?

  1. Rutin
  2. Hypericin
  3. Barbaloin Correct answer.
  4. Berberine

Explanation

Barbaloin (aloin) is the C-glycosyl anthrone characteristic of Aloe species and is used as the identity marker for aloe latex. Hypericin is a naphthodianthrone from Hypericum, rutin is a flavonol glycoside, and berberine is a protoberberine alkaloid from Berberis and Coptis.