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PEBC Part I (MCQ) study materials
PEBC Part I (MCQ) study resources

PEBC Part I (MCQ) practice questions

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Question 1Biomedical sciences (anatomy, physiology, pathophysiology, microbiology, immunology, biochemistry)

Which cardiac valve is located between the right ventricle and the pulmonary trunk?

  1. Mitral valve
  2. Tricuspid valve
  3. Aortic valve
  4. Pulmonary valve Correct answer.

Explanation

The pulmonary valve guards the right ventricular outflow tract and opens into the pulmonary trunk during systole. The aortic valve is located at the left ventricular outflow tract, while the tricuspid and mitral valves are atrioventricular valves. Therefore, the structure between the right ventricle and pulmonary trunk is the pulmonary valve.

Question 2Biomedical sciences (anatomy, physiology, pathophysiology, microbiology, immunology, biochemistry)

Which membrane property is the principal direct determinant of the resting membrane potential of a typical neuron?

  1. High resting permeability to sodium
  2. High resting permeability to potassium Correct answer.
  3. Active chloride secretion by the sodium-potassium pump
  4. Rapid calcium influx through voltage-gated channels

Explanation

At rest, neuronal membranes are much more permeable to potassium than to sodium because of open potassium leak channels. The potassium concentration gradient therefore dominates the resting membrane potential, which sits near the potassium equilibrium potential. Sodium permeability is low at rest, and calcium influx mainly occurs during excitation.

Question 3Biomedical sciences (anatomy, physiology, pathophysiology, microbiology, immunology, biochemistry)

Which feature is characteristic of the cell wall of Gram-positive bacteria?

  1. An outer membrane containing lipopolysaccharide and porins
  2. Absence of a cell wall
  3. A thick peptidoglycan layer with teichoic acids Correct answer.
  4. A waxy layer rich in mycolic acid

Explanation

Gram-positive bacteria have a thick peptidoglycan layer that retains the crystal violet-iodine complex during Gram staining, and teichoic acids are embedded in this wall. Lipopolysaccharide and porins are features of the Gram-negative outer membrane, while mycolic acid characterizes acid-fast organisms. Mycoplasma species lack a cell wall, but that is not a Gram-positive feature.

Question 4Biomedical sciences (anatomy, physiology, pathophysiology, microbiology, immunology, biochemistry)

Which immunoglobulin is the principal antibody found in mucosal secretions such as saliva and breast milk?

  1. IgA Correct answer.
  2. IgM
  3. IgE
  4. IgG

Explanation

Secretory IgA is a dimeric antibody transported across mucosal epithelium and is the dominant immunoglobulin in saliva, tears, breast milk, and respiratory and gastrointestinal secretions. IgG predominates in serum and crosses the placenta, IgM is the primary response antibody, and IgE mediates allergic reactions.

Question 5Biomedical sciences (anatomy, physiology, pathophysiology, microbiology, immunology, biochemistry)

Which enzyme catalyzes the major rate-limiting step of glycolysis?

  1. Hexokinase
  2. Glucose-6-phosphatase
  3. Phosphofructokinase-1 Correct answer.
  4. Fructose-1,6-bisphosphatase

Explanation

Phosphofructokinase-1 converts fructose-6-phosphate to fructose-1,6-bisphosphate and is the key allosterically regulated, rate-limiting enzyme of glycolysis. Hexokinase catalyzes the first phosphorylation but is not the major controlling step, and the other two enzymes participate in gluconeogenesis rather than glycolysis.

Question 6Biomedical sciences (anatomy, physiology, pathophysiology, microbiology, immunology, biochemistry)

What is the primary underlying defect in type 1 diabetes mellitus?

  1. Insulin resistance in skeletal muscle
  2. Autoimmune destruction of pancreatic beta cells Correct answer.
  3. Excessive glucagon secretion from alpha cells
  4. Increased renal glucose reabsorption

Explanation

Type 1 diabetes results from T-cell-mediated autoimmune destruction of pancreatic beta cells, leading to absolute insulin deficiency. Insulin resistance characterizes type 2 diabetes, while glucagon excess and increased renal glucose reabsorption are secondary or contributory abnormalities rather than the primary defect.

Question 7Biomedical sciences (anatomy, physiology, pathophysiology, microbiology, immunology, biochemistry)

Which nerve provides the motor innervation to the diaphragm?

  1. Phrenic nerve Correct answer.
  2. Vagus nerve
  3. Intercostal nerves
  4. Recurrent laryngeal nerve

Explanation

The phrenic nerve arises from cervical roots C3 to C5 and supplies the motor innervation to the diaphragm. The vagus nerve provides parasympathetic innervation to thoracic and abdominal organs, intercostal nerves supply intercostal muscles, and the recurrent laryngeal nerve innervates laryngeal muscles.

Question 8Biomedical sciences (anatomy, physiology, pathophysiology, microbiology, immunology, biochemistry)

At the arterial end of a systemic capillary, which force primarily drives fluid out of the capillary into the interstitium?

  1. Plasma oncotic pressure
  2. Capillary hydrostatic pressure Correct answer.
  3. Lymphatic contractility
  4. Interstitial hydrostatic pressure

Explanation

Capillary hydrostatic pressure reflects the blood pressure within the capillary and is the main outward Starling force at the arterial end. Plasma oncotic pressure pulls fluid back into the capillary, while interstitial hydrostatic pressure opposes filtration. Lymphatic contractility removes excess interstitial fluid but does not drive capillary filtration.

Question 9Biomedical sciences (anatomy, physiology, pathophysiology, microbiology, immunology, biochemistry)

What is the primary mechanism of action of beta-lactam antibiotics?

  1. Inhibition of the 30S ribosomal subunit
  2. Inhibition of DNA gyrase
  3. Inhibition of cell wall transpeptidation Correct answer.
  4. Inhibition of fungal ergosterol synthesis

Explanation

Beta-lactams acylate penicillin-binding proteins, which are bacterial transpeptidases, and thereby block peptidoglycan cross-linking in the cell wall. This weakens the wall and promotes bacterial lysis, especially in actively dividing organisms. Ribosomal 30S inhibition, DNA gyrase inhibition, and ergosterol synthesis inhibition belong to other antibiotic classes.

Question 10Biomedical sciences (anatomy, physiology, pathophysiology, microbiology, immunology, biochemistry)

MHC class I molecules present endogenous peptides primarily to which cell type?

  1. CD4-positive helper T cells
  2. CD8-positive cytotoxic T cells Correct answer.
  3. CD4-positive regulatory T cells
  4. Natural killer cells

Explanation

MHC class I molecules are expressed on nearly all nucleated cells and display cytosolic peptides to CD8-positive cytotoxic T lymphocytes. MHC class II molecules instead present exogenous peptides to CD4-positive helper T cells. Natural killer cells use MHC-independent recognition and are not the primary peptide-specific responders to MHC class I.

Question 11Biomedical sciences (anatomy, physiology, pathophysiology, microbiology, immunology, biochemistry)

Deficiency of which enzyme causes classic phenylketonuria?

  1. Branched-chain alpha-ketoacid dehydrogenase
  2. Homogentisate oxidase
  3. Phenylalanine hydroxylase Correct answer.
  4. Tyrosinase

Explanation

Classic phenylketonuria is caused by deficient phenylalanine hydroxylase, which converts phenylalanine to tyrosine. The block causes phenylalanine accumulation and alternative metabolite formation that can damage the developing brain. Tyrosinase deficiency causes albinism, homogentisate oxidase deficiency causes alkaptonuria, and branched-chain alpha-ketoacid dehydrogenase deficiency causes maple syrup urine disease.

Question 12Biomedical sciences (anatomy, physiology, pathophysiology, microbiology, immunology, biochemistry)

Anemia in advanced chronic kidney disease is most directly caused by inadequate production of which hormone?

  1. Atrial natriuretic peptide
  2. Calcitriol
  3. Aldosterone
  4. Erythropoietin Correct answer.

Explanation

Erythropoietin is produced mainly by peritubular interstitial fibroblasts in the kidney and stimulates proliferation of erythroid progenitors. In advanced chronic kidney disease, loss of functional renal mass reduces erythropoietin production and causes normocytic normochromic anemia. Aldosterone, calcitriol, and natriuretic peptides do not directly stimulate red blood cell production.

Question 13Biomedical sciences (anatomy, physiology, pathophysiology, microbiology, immunology, biochemistry)

Which three structures make up the portal triad in the liver?

  1. Hepatic vein, inferior vena cava, and bile duct
  2. Portal vein, hepatic vein, and hepatic artery
  3. Central vein, bile canaliculus, and hepatic artery
  4. Proper hepatic artery, portal vein, and bile duct Correct answer.

Explanation

The portal triad consists of a branch of the proper hepatic artery, a branch of the portal vein, and a bile duct, all enclosed within connective tissue at the periphery of the hepatic lobule. The hepatic vein and inferior vena cava drain blood away from the liver and are not part of the triad. The central vein lies at the center of the lobule.

Question 14Biomedical sciences (anatomy, physiology, pathophysiology, microbiology, immunology, biochemistry)

Which hormone raises serum calcium by stimulating bone resorption and renal tubular calcium reabsorption?

  1. Parathyroid hormone Correct answer.
  2. Calcitonin
  3. Atrial natriuretic peptide
  4. Aldosterone

Explanation

Parathyroid hormone increases serum calcium through direct actions on bone and kidney and indirect actions on intestine via calcitriol. It stimulates osteoclastic bone resorption and increases distal renal tubular calcium reabsorption. Calcitonin lowers serum calcium, while natriuretic peptide and aldosterone primarily regulate sodium balance and blood pressure.

Question 15Biomedical sciences (anatomy, physiology, pathophysiology, microbiology, immunology, biochemistry)

Which statement best contrasts exotoxins with endotoxins?

  1. Exotoxins are heat-labile proteins, whereas endotoxins are heat-stable lipopolysaccharides Correct answer.
  2. Exotoxins act only by activating Toll-like receptor 4, whereas endotoxins act enzymatically on host cells
  3. Exotoxins are heat-stable lipopolysaccharides, whereas endotoxins are heat-labile proteins
  4. Exotoxins are produced only by Gram-negative bacteria, whereas endotoxins are produced by Gram-positive bacteria

Explanation

Exotoxins are typically heat-labile proteins secreted by living bacteria and often act enzymatically on specific host targets. Endotoxins are heat-stable lipopolysaccharides from the outer membrane of Gram-negative bacteria and signal through Toll-like receptor 4. This contrast explains why endotoxins withstand heat and are not actively secreted proteins.

Question 16Biomedical sciences (anatomy, physiology, pathophysiology, microbiology, immunology, biochemistry)

What is the principal role of C3b in complement activation?

  1. Chemotaxis of neutrophils
  2. Anaphylatoxin-mediated mast cell degranulation
  3. Opsonization of microbial surfaces Correct answer.
  4. Formation of the membrane attack complex pore

Explanation

C3b covalently attaches to microbial surfaces and acts as a major opsonin, promoting recognition and phagocytosis by complement receptors on phagocytes. C5b initiates assembly of the membrane attack complex, while C3a and C5a are anaphylatoxins and C5a also promotes chemotaxis. Thus C3b primarily enhances phagocytic clearance rather than direct lysis.

Question 17Biomedical sciences (anatomy, physiology, pathophysiology, microbiology, immunology, biochemistry)

Which enzyme catalyzes the rate-limiting step of heme biosynthesis in hepatocytes?

  1. Ferrochelatase
  2. ALA synthase Correct answer.
  3. Porphobilinogen deaminase
  4. ALA dehydratase

Explanation

ALA synthase condenses glycine and succinyl-CoA to form delta-aminolevulinic acid, and this reaction is the rate-limiting step of heme synthesis. Hepatic ALA synthase is regulated by heme availability and drug-induced cytochrome P450 demand. The other enzymes act at later steps in the pathway.

Question 18Biomedical sciences (anatomy, physiology, pathophysiology, microbiology, immunology, biochemistry)

Edema in nephrotic syndrome is primarily attributable to which mechanism?

  1. Lymphatic obstruction by protein casts
  2. Increased capillary hydrostatic pressure from sodium retention
  3. Primary hyperaldosteronism causing sodium reabsorption
  4. Reduced plasma oncotic pressure from hypoalbuminemia Correct answer.

Explanation

Nephrotic syndrome causes heavy urinary albumin loss, lowering plasma albumin and reducing plasma oncotic pressure. This favors movement of fluid from the vascular compartment into the interstitium and produces edema. Sodium retention can contribute secondarily, but hypoalbuminemia is the primary driving mechanism.

Question 19Biomedical sciences (anatomy, physiology, pathophysiology, microbiology, immunology, biochemistry)

Which lung volume cannot be measured directly by simple spirometry?

  1. Tidal volume
  2. Expiratory reserve volume
  3. Inspiratory reserve volume
  4. Residual volume Correct answer.

Explanation

Residual volume is the air remaining in the lungs after a maximal forced expiration, so it cannot be exhaled into a spirometer. It is measured indirectly by helium dilution, nitrogen washout, or body plethysmography. Tidal, inspiratory reserve, and expiratory reserve volumes are all exchangeable with the spirometer and can be measured directly.

Question 20Biomedical sciences (anatomy, physiology, pathophysiology, microbiology, immunology, biochemistry)

In which nephron segment is the largest fraction of filtered water reabsorbed?

  1. Descending limb of the loop of Henle
  2. Proximal convoluted tubule Correct answer.
  3. Distal convoluted tubule
  4. Collecting duct

Explanation

The proximal convoluted tubule reabsorbs approximately 65% of filtered water along with sodium and other solutes in an iso-osmotic manner. The descending limb, distal tubule, and collecting duct reabsorb smaller fractions, with the collecting duct subject to hormonal regulation by vasopressin and aldosterone. Therefore, the largest fraction of filtered water is reclaimed proximally.

Question 21Pharmaceutical sciences (pharmaceutics, pharmacology, medicinal chemistry, pharmacokinetics)

For a drug that is extensively extracted by the liver, which route of administration avoids hepatic first-pass metabolism entirely?

  1. Enteric-coated oral tablet
  2. Intravenous injection Correct answer.
  3. Oral tablet
  4. Rectal suppository

Explanation

Drug absorbed from the gut or rectum enters the portal circulation and passes through the liver before reaching the systemic circulation, so first-pass extraction reduces bioavailability. Intravenous administration delivers the full dose directly into the systemic circulation, bypassing the gut wall and liver entirely. Rectal absorption avoids first-pass only partially, because the upper rectum drains into the portal vein.

Question 22Pharmaceutical sciences (pharmaceutics, pharmacology, medicinal chemistry, pharmacokinetics)

The bactericidal action of penicillins against susceptible bacteria results from interference with which process?

  1. Dihydrofolate reductase inhibition
  2. Inhibition of DNA gyrase
  3. Binding to the 30S ribosomal subunit
  4. Cross-linking of peptidoglycan chains Correct answer.

Explanation

Beta-lactam antibiotics acylate the transpeptidase enzymes (penicillin-binding proteins) that cross-link peptidoglycan, weakening the cell wall so that the osmotically fragile bacterium lyses. This mechanism requires actively dividing organisms, which explains why penicillins are bactericidal rather than static.

Question 23Pharmaceutical sciences (pharmaceutics, pharmacology, medicinal chemistry, pharmacokinetics)

In a wet-granulated tablet formulation, povidone (polyvinylpyrrolidone) is included primarily to act as which type of excipient?

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

Explanation

Povidone is dissolved or dispersed in the granulating fluid so that it adheres powder particles together, giving granules that flow and compress well; it is therefore classified as a binder. Lubricants and glidants modify powder flow and ejection rather than promoting granule cohesion, and disintegrants act after ingestion to break the tablet apart.

Question 24Pharmaceutical sciences (pharmaceutics, pharmacology, medicinal chemistry, pharmacokinetics)

A reversible competitive antagonist is added to a tissue bath containing an agonist at equilibrium. What change is expected in the agonist log concentration–response curve?

  1. A parallel rightward shift with a reduced maximum response
  2. No change in EC50 but a reduced maximum response
  3. A parallel rightward shift with an unchanged maximum response Correct answer.
  4. A leftward shift with an increased maximum response

Explanation

Because a competitive antagonist binds reversibly at the same site as the agonist, sufficiently high agonist concentrations can displace it, so the maximum response is preserved. The concentration of agonist needed to occupy a given fraction of receptors is increased, producing a parallel rightward shift of the curve with unchanged Emax.

Question 25Pharmaceutical sciences (pharmaceutics, pharmacology, medicinal chemistry, pharmacokinetics)

For a drug that follows linear (first-order) one-compartment kinetics, the elimination half-life is calculated by which expression?

  1. CL / Vd
  2. 0.693 × CL / Vd
  3. 0.693 × Vd / CL Correct answer.
  4. Vd × CL

Explanation

The elimination rate constant k equals clearance divided by volume of distribution, and half-life is ln2 divided by k. Substituting gives t½ = 0.693 × Vd / CL, so half-life lengthens when volume of distribution increases or clearance falls.

Question 26Pharmaceutical sciences (pharmaceutics, pharmacology, medicinal chemistry, pharmacokinetics)

Enalapril is given as a prodrug rather than as the active enalaprilat. Which statement best explains this design?

  1. The prodrug avoids hepatic first-pass metabolism entirely
  2. It is absorbed by the peptide transporter PEPT1, improving oral absorption Correct answer.
  3. Enalaprilat is unstable at gastric pH and is destroyed in the stomach
  4. Enalaprilat is too lipophilic to reach the active site of ACE

Explanation

The dicarboxylic acid enalaprilat is highly ionized and poorly permeant, so it is absorbed only slightly when given orally. Esterifying one carboxyl group gives enalapril, which is recognized by the intestinal peptide transporter PEPT1 and absorbed well, then hydrolysed by esterases to release enalaprilat.

Question 27Pharmaceutical sciences (pharmaceutics, pharmacology, medicinal chemistry, pharmacokinetics)

Phenytoin shows saturable, zero-order elimination at concentrations above the therapeutic range. If the daily dose is increased by 100 mg in such a patient, what is the expected result?

  1. Plasma concentration rises in direct proportion to the dose increase
  2. Steady state is reached more quickly after the increase
  3. Plasma concentration falls because clearance increases at higher concentrations
  4. Plasma concentration rises disproportionately and toxicity may occur Correct answer.

Explanation

Once metabolizing enzymes are saturated, a constant amount of drug is eliminated per unit time regardless of concentration, so the increment in dose is not matched by an increase in elimination. The extra drug accumulates, and a small dose increase can produce a large, unpredictable rise in plasma concentration with nystagmus, ataxia and other toxicity.

Question 28Pharmaceutical sciences (pharmaceutics, pharmacology, medicinal chemistry, pharmacokinetics)

Atropine causes mydriasis, dry mouth and urinary retention. Blockade of which receptor subtype accounts for these effects?

  1. Nicotinic Nn receptors
  2. Beta-2 adrenergic receptors
  3. Muscarinic M3 receptors Correct answer.
  4. Alpha-1 adrenergic receptors

Explanation

Parasympathetic tone mediated by muscarinic M3 receptors drives pupillary constriction, salivary and bronchial secretion, and detrusor contraction. Atropine is a competitive antagonist at these receptors, so blockade produces mydriasis, xerostomia and urinary retention. Nicotinic receptors mediate ganglionic and neuromuscular transmission rather than these end-organ effects.

Question 29Pharmaceutical sciences (pharmaceutics, pharmacology, medicinal chemistry, pharmacokinetics)

According to the Noyes–Whitney relationship, which change would most increase the dissolution rate of a poorly water-soluble drug powder?

  1. Milling to a smaller particle size Correct answer.
  2. Increasing the particle size to reduce the surface area
  3. Reducing the volume of the dissolution medium
  4. Coating the particles with magnesium stearate

Explanation

The Noyes–Whitney equation states that dissolution rate is proportional to the surface area of solid exposed to the solvent and to the concentration gradient. Reducing particle size greatly increases the specific surface area, so the dissolution rate rises and absorption of a dissolution-limited drug improves.

Question 30Pharmaceutical sciences (pharmaceutics, pharmacology, medicinal chemistry, pharmacokinetics)

A 70 kg patient requires a loading dose of a drug with a volume of distribution of 0.5 L/kg and a target plasma concentration of 4 mg/L. Systemic bioavailability of the intravenous product is complete. What loading dose is required?

  1. 70 mg
  2. 140 mg Correct answer.
  3. 35 mg
  4. 280 mg

Explanation

Loading dose equals volume of distribution multiplied by the target concentration divided by bioavailability. Vd is 0.5 L/kg × 70 kg = 35 L, and 35 L × 4 mg/L = 140 mg. The calculation is independent of clearance because it only fills the apparent distribution volume.

Question 31Pharmaceutical sciences (pharmaceutics, pharmacology, medicinal chemistry, pharmacokinetics)

Which physicochemical profile best predicts passive penetration of the blood–brain barrier by a small-molecule drug?

  1. Moderate lipophilicity and low polar surface area Correct answer.
  2. High aqueous solubility at physiological pH
  3. Extensive ionization at pH 7.4
  4. A molecular weight greater than 800 Da

Explanation

The blood–brain barrier is a tight-junction endothelium with high lipid content, so passive entry favours small, uncharged molecules with moderate lipophilicity (logP roughly 1–3) and low polar surface area. Excessive polarity, charge or molecular size limits transcellular diffusion regardless of aqueous solubility.

Question 32Pharmaceutical sciences (pharmaceutics, pharmacology, medicinal chemistry, pharmacokinetics)

Repeated dosing with ephedrine over several days produces rapidly diminishing pressor responses. This tachyphylaxis is best explained by which mechanism?

  1. Formation of neutralizing antibodies against the drug
  2. Rapid phosphorylation and internalization of beta receptors
  3. Depletion of presynaptic noradrenaline stores Correct answer.
  4. Competitive blockade of the receptor by a metabolite

Explanation

Ephedrine acts largely indirectly by displacing noradrenaline from vesicular stores in sympathetic nerve terminals. When stores are depleted faster than they are replenished, the same dose releases less transmitter and the response wanes, a classic form of tachyphylaxis.

Question 33Pharmaceutical sciences (pharmaceutics, pharmacology, medicinal chemistry, pharmacokinetics)

An elementary osmotic pump tablet releases drug at a nearly constant rate for most of its dosing interval because of which property?

  1. An enteric coating dissolves slowly in the small intestine
  2. The drug dissolves immediately on contact with gastric fluid
  3. Water enters at a constant rate through the semipermeable membrane Correct answer.
  4. Drug is released by zero-order erosion of the polymer matrix

Explanation

In an osmotic pump, water crosses the semipermeable membrane at a rate governed by the osmotic pressure difference across it, which remains essentially constant while undissolved drug remains in the core. The resulting volume flux pushes dissolved drug out through the delivery orifice at a zero-order rate.

Question 34Pharmaceutical sciences (pharmaceutics, pharmacology, medicinal chemistry, pharmacokinetics)

In a patient with marked hypoalbuminaemia taking a highly protein-bound drug with low hepatic extraction, which measurement best guides dose adjustment?

  1. Urinary excretion rate of total drug
  2. Unbound (free) plasma concentration Correct answer.
  3. Red blood cell count
  4. Total plasma concentration

Explanation

Only the unbound fraction is able to distribute to tissues and interact with receptors, so it is the determinant of effect. With low-extraction drugs and reduced albumin, total concentration falls while free concentration may remain normal, so interpreting total concentration alone would lead to unnecessary dose escalation.

Question 35Pharmaceutical sciences (pharmaceutics, pharmacology, medicinal chemistry, pharmacokinetics)

Clarithromycin is co-prescribed with simvastatin, and the patient develops muscle pain and a raised creatine kinase. Which mechanism best explains this interaction?

  1. Reduced gastric absorption of simvastatin
  2. Displacement of simvastatin from plasma protein binding sites
  3. Induction of CYP3A4 lowers simvastatin exposure
  4. Inhibition of CYP3A4 increases simvastatin exposure Correct answer.

Explanation

Simvastatin undergoes extensive first-pass metabolism by CYP3A4, and clarithromycin is a strong mechanism-based inhibitor of that enzyme. Concentrations of simvastatin and its active acid rise several-fold, increasing the risk of myopathy and rhabdomyolysis.

Question 36Pharmaceutical sciences (pharmaceutics, pharmacology, medicinal chemistry, pharmacokinetics)

Which formulation strategy is most appropriate for a drug that undergoes rapid acid–base-catalysed hydrolysis in aqueous solution?

  1. Increase the water content of the vehicle
  2. Lyophilize the product and reconstitute immediately before use Correct answer.
  3. Store the solution at elevated temperature
  4. Add a chelating agent to sequester trace metal ions and prevent oxidation

Explanation

Hydrolysis requires water, so removing water by lyophilization essentially stops the degradation and gives a stable powder with a long shelf life. The product is reconstituted with a suitable diluent just before administration and then used within its short in-use period.

Question 37Pharmaceutical sciences (pharmaceutics, pharmacology, medicinal chemistry, pharmacokinetics)

A drug shows a secondary plasma concentration peak 6–8 hours after oral dosing and a terminal half-life longer than predicted from its clearance. Which process best explains these findings?

  1. Saturable plasma protein binding
  2. Delayed gastric emptying of the dose
  3. Redistribution from a deep compartment
  4. Enterohepatic recirculation of the drug Correct answer.

Explanation

Drug excreted in bile reaches the intestine, where bacterial enzymes may regenerate the absorbable parent compound, allowing it to be reabsorbed and creating a second peak. Repeated cycles of biliary excretion and reabsorption act as a reservoir that prolongs the terminal half-life beyond what clearance alone would predict.

Question 38Pharmaceutical sciences (pharmaceutics, pharmacology, medicinal chemistry, pharmacokinetics)

Warfarin is given as a racemate; S-warfarin is three to five times more potent than R-warfarin as an inhibitor of vitamin K epoxide reductase. Which statement is correct?

  1. S-warfarin is excreted unchanged by the kidney
  2. Both enantiomers are equipotent so assay selectivity is irrelevant
  3. R-warfarin is cleared mainly by CYP2C9
  4. CYP2C9 inhibition preferentially raises S-warfarin exposure Correct answer.

Explanation

The two enantiomers are handled by different enzymes: S-warfarin, the more active enantiomer, is metabolized principally by CYP2C9, while R-warfarin is cleared by CYP1A2 and CYP3A4. A CYP2C9 inhibitor such as fluconazole therefore raises exposure to the more potent enantiomer and produces a greater anticoagulant effect than a change in total warfarin concentration alone would suggest.

Question 39Pharmaceutical sciences (pharmaceutics, pharmacology, medicinal chemistry, pharmacokinetics)

An 80-year-old woman weighing 60 kg has a serum creatinine of 1.2 mg/dL. Using the Cockcroft–Gault equation, her estimated creatinine clearance is closest to which value?

  1. 35 mL/min Correct answer.
  2. 60 mL/min
  3. 18 mL/min
  4. 42 mL/min

Explanation

Cockcroft–Gault gives CrCl = (140 − age) × weight / (72 × serum creatinine), multiplied by 0.85 for women. Here (140 − 80) × 60 / (72 × 1.2) = 41.7 mL/min, and applying the female factor gives approximately 35 mL/min, which corresponds to moderate renal impairment requiring dose review.

Question 40Pharmaceutical sciences (pharmaceutics, pharmacology, medicinal chemistry, pharmacokinetics)

A patient is identified as a CYP2D6 ultrarapid metabolizer. What is the expected consequence of standard-dose codeine therapy?

  1. Absence of analgesia because codeine is not converted to morphine
  2. Reduced formation of morphine, causing loss of analgesia, as seen in poor metabolizers of CYP2D6
  3. Greater morphine formation, so more analgesia but a risk of respiratory depression Correct answer.
  4. Higher plasma codeine concentrations with an unchanged analgesic effect

Explanation

Codeine is a prodrug that requires O-demethylation by CYP2D6 to morphine, the active analgesic. Ultrarapid metabolizers convert codeine unusually quickly and can achieve morphine concentrations associated with exaggerated analgesia and life-threatening respiratory depression, which is why codeine is avoided in this genotype.

Question 41Pharmacy practice and pharmacotherapy (assessment, therapeutic decision-making, monitoring)

A 62-year-old patient with type 2 diabetes and hypertension is started on ramipril. Which laboratory parameters should be monitored after initiation and dose increases?

  1. Serum potassium and serum creatinine Correct answer.
  2. Fasting glucose and hemoglobin A1c
  3. Thyroid-stimulating hormone and free T4
  4. INR and platelet count

Explanation

Angiotensin-converting enzyme inhibitors reduce aldosterone production and can raise serum potassium and worsen kidney function, especially in patients with chronic kidney disease or volume depletion. Baseline and follow-up measurement of potassium and creatinine within one to two weeks of starting therapy or increasing the dose is standard practice.

Question 42Pharmacy practice and pharmacotherapy (assessment, therapeutic decision-making, monitoring)

Which agent is the specific antidote for warfarin-associated coagulopathy?

  1. Andexanet alfa
  2. Idarucizumab
  3. Vitamin K (phytonadione) Correct answer.
  4. Protamine sulfate

Explanation

Warfarin inhibits vitamin K epoxide reductase, reducing synthesis of clotting factors II, VII, IX, and X. Vitamin K replenishes the cofactor needed for their activation and is the specific reversal agent for warfarin.

Question 43Pharmacy practice and pharmacotherapy (assessment, therapeutic decision-making, monitoring)

In a region with high pneumococcal macrolide resistance, an otherwise healthy 45-year-old nonsmoker is diagnosed with uncomplicated community-acquired pneumonia and will be treated as an outpatient. Which empiric antibiotic is most appropriate?

  1. Levofloxacin
  2. Amoxicillin Correct answer.
  3. Azithromycin
  4. Trimethoprim-sulfamethoxazole

Explanation

Amoxicillin is the preferred empiric agent for uncomplicated community-acquired pneumonia in otherwise healthy outpatients, particularly when local pneumococcal macrolide resistance is high. Respiratory fluoroquinolones are generally reserved for patients with comorbidities or recent antibiotic exposure.

Question 44Pharmacy practice and pharmacotherapy (assessment, therapeutic decision-making, monitoring)

Which antihypertensive class is most strongly associated with a persistent dry cough?

  1. Dihydropyridine calcium channel blockers
  2. Angiotensin II receptor blockers
  3. Angiotensin-converting enzyme inhibitors Correct answer.
  4. Thiazide diuretics

Explanation

Angiotensin-converting enzyme inhibitors reduce bradykinin breakdown, and bradykinin accumulation is thought to cause the persistent dry cough reported in a substantial minority of patients. Switching to an angiotensin II receptor blocker usually resolves the cough because ARBs do not inhibit bradykinin metabolism.

Question 45Pharmacy practice and pharmacotherapy (assessment, therapeutic decision-making, monitoring)

Which insulin product has a duration of action suitable for once-daily basal coverage?

  1. Insulin glargine Correct answer.
  2. Insulin lispro
  3. Insulin aspart
  4. Regular human insulin

Explanation

Insulin glargine is a long-acting basal insulin with a relatively flat profile lasting approximately 24 hours, allowing once-daily dosing in many patients. Lispro and aspart are rapid-acting mealtime insulins, while regular insulin has a shorter duration than glargine.

Question 46Pharmacy practice and pharmacotherapy (assessment, therapeutic decision-making, monitoring)

A patient starting isoniazid for latent tuberculosis should receive which vitamin to prevent peripheral neuropathy?

  1. Folic acid
  2. Cyanocobalamin
  3. Pyridoxine Correct answer.
  4. Thiamine

Explanation

Isoniazid interferes with pyridoxine metabolism and can cause peripheral neuropathy, so pyridoxine supplementation is routinely given with isoniazid. The supplement does not treat tuberculosis but prevents this predictable adverse effect.

Question 47Pharmacy practice and pharmacotherapy (assessment, therapeutic decision-making, monitoring)

A patient taking warfarin for atrial fibrillation has an INR of 5.6 and no bleeding. What is the most appropriate initial management?

  1. Continue the current warfarin dose and recheck the INR in 1 week
  2. Start a therapeutic heparin infusion until the INR falls
  3. Give intravenous vitamin K 10 mg and fresh frozen plasma
  4. Hold warfarin for 1 to 2 doses and recheck the INR Correct answer.

Explanation

For an INR between 5 and 9 without bleeding, usual management is to omit one or two warfarin doses and monitor the INR rather than give routine vitamin K. Intravenous vitamin K and fresh frozen plasma are reserved for major bleeding or very high INR with high bleeding risk.

Question 48Pharmacy practice and pharmacotherapy (assessment, therapeutic decision-making, monitoring)

A patient with type 2 diabetes has an eGFR of 28 mL/min/1.73 m2. What is the most appropriate action regarding metformin?

  1. Continue the current dose unchanged
  2. Increase the dose to improve glycemic control
  3. Discontinue metformin Correct answer.
  4. Add a second biguanide

Explanation

Metformin is contraindicated when the eGFR falls below 30 mL/min/1.73 m2 because of the increased risk of lactic acidosis. It should not be initiated in this range and should be discontinued in a patient already taking it.

Question 49Pharmacy practice and pharmacotherapy (assessment, therapeutic decision-making, monitoring)

Which medication is most likely to increase the INR when added to warfarin therapy?

  1. Amiodarone Correct answer.
  2. Rifampin
  3. St. John's wort
  4. Carbamazepine

Explanation

Amiodarone inhibits CYP2C9 and CYP3A4, reducing warfarin metabolism and often raising the INR. Patients starting amiodarone with warfarin need closer INR monitoring and may require a warfarin dose reduction.

Question 50Pharmacy practice and pharmacotherapy (assessment, therapeutic decision-making, monitoring)

A patient with asthma uses salbutamol two or three times per week for symptom relief. According to current asthma guidelines, what is the preferred next step?

  1. Add montelukast
  2. Add a long-acting beta2-agonist
  3. Start a low-dose inhaled corticosteroid Correct answer.
  4. Double the salbutamol dose

Explanation

Reliever use more than twice weekly suggests inadequate asthma control, and inhaled corticosteroid therapy is the cornerstone of controller treatment. Long-acting beta2-agonists should not be used as monotherapy in asthma because of safety concerns.