SP PHAR 6112 Final Exam Chicago State University School of Pharmacy

Explanation:

Correct Answer: (B) Franz Cell

The Franz diffusion cell is the gold standard in vitro model used to evaluate the skin penetration and permeation of topically and dermatologically applied drugs. It consists of a donor compartment where the drug formulation is applied to a membrane (or excised skin), and a receptor compartment filled with a physiological fluid that simulates the conditions beneath the skin. Samples are taken from the receptor compartment at timed intervals to measure the amount of drug that has penetrated through the skin, providing critical data for the development of topical formulations.

Why Other Options are Incorrect:

A. Laser Abrasion — Laser abrasion is a physical skin enhancement technique used to improve drug penetration in vivo by removing the outer layers of the stratum corneum. It is not an in vitro model for evaluating drug penetration.

C. Derma roller — A derma roller is a microneedling device used to create microchannels in the skin to enhance transdermal drug delivery in vivo. It is a physical penetration enhancement method, not an in vitro evaluation model.

D. Distek apparatus — The Distek apparatus is a dissolution testing instrument used to evaluate drug release from oral dosage forms such as tablets and capsules. It is not designed for evaluating dermatological drug penetration.

Explanation:

Correct Answer: (A) Intestine

Enteric coated tablets have a special polymer coating that is resistant to the acidic environment of the stomach (pH 1–3) but dissolves in the more alkaline environment of the small intestine (pH 6–7). This design serves two purposes: it protects acid-sensitive drugs from degradation in the stomach, and it protects the gastric mucosa from drugs that can cause irritation or ulceration. Drug release and absorption therefore occur in the intestine, not the stomach.

Why Other Options are Incorrect:

B. Mouth — Drug release in the mouth is the function of sublingual tablets, buccal tablets, or orally disintegrating tablets, not enteric coated tablets, which are designed to remain intact until they reach the intestine.

C. Rectum — Rectal drug delivery is achieved through suppositories or rectal solutions, not enteric coated tablets which are oral dosage forms designed for intestinal release.

D. Stomach — The entire purpose of enteric coating is to prevent drug release in the stomach. The coating is specifically engineered to resist gastric acid and remain intact until it reaches the higher pH environment of the intestine.

Explanation:

Correct Answer: (A) Crystallization

Crystallization is a fundamental pharmaceutical manufacturing process used both to form and to purify active pharmaceutical ingredients (APIs). In this process, a drug substance is dissolved in a solvent at high temperature and then allowed to cool or concentrate, causing the pure drug to precipitate out as highly ordered crystals. Impurities remain in solution and are separated from the purified drug crystals. Crystallization is widely used in pharmaceutical production because it yields APIs of high purity, defined crystal structure, and consistent physical properties such as melting point, solubility, and bioavailability.

Why Other Options are Incorrect:

B. Oxidation — Oxidation is a chemical degradation process in which a drug molecule loses electrons or reacts with oxygen, leading to chemical breakdown and loss of drug potency. It is a cause of pharmaceutical instability, not a method of API formation or purification.

C. Racemization — Racemization is a chemical process in which an optically pure enantiomer (chiral drug) is converted into an equal mixture of both enantiomers (a racemic mixture). This is generally an undesirable process in pharmaceutical production as it can reduce drug efficacy and introduce unwanted stereoisomers with different pharmacological profiles.

D. Reduction — Reduction is an electrochemical process involving the gain of electrons by a molecule. While reduction reactions are used in some synthetic chemistry steps, it is not specifically identified as a general process for the formation and purification of APIs in the way that crystallization is.

Explanation:

Correct Answer: (C) Active hepatic first pass

The three principal processes that determine urinary excretion of a drug are glomerular filtration, active tubular secretion, and tubular reabsorption — all of which occur in the kidney as illustrated in the attached nephron diagram. The hepatic first pass effect refers to the metabolism of a drug by the liver before it reaches systemic circulation and is a process of hepatic metabolism, not renal excretion. It has no role in determining urinary drug excretion.

Why Other Options are Incorrect:

A. Active tubular secretion — This is a primary renal excretion process where drug molecules are actively transported from the peritubular capillaries into the renal tubular lumen for excretion in urine.

B. Active or passive tubular reabsorption — Tubular reabsorption is a key process in renal drug excretion where drug molecules in the tubular filtrate are reabsorbed back into the bloodstream, reducing the amount excreted in urine.

D. Glomerular filtration — Glomerular filtration is the first and primary step in renal drug excretion, where unbound drug molecules are filtered from the blood through the glomerular capillaries into the Bowman's capsule to begin the process of urinary excretion.

Explanation:

Correct Answer: (D) A measure of acidity

pH is defined as the negative logarithm of the hydrogen ion concentration and serves as a quantitative measure of the acidity or alkalinity of a solution. A pH below 7 indicates an acidic solution, a pH of 7 is neutral, and a pH above 7 indicates an alkaline (basic) solution. It is the standard scale used in chemistry and pharmacology to express the degree of acidity or basicity of a substance.

Why Other Options are Incorrect:

A. Extent of dissociation of acids — The extent of acid dissociation is expressed by the acid dissociation constant (Ka) or its logarithmic form (pKa), not pH. While pH is influenced by acid dissociation, it is not itself a measure of the extent of dissociation.

B. The same as pOH — pH and pOH are related but not the same. They are complementary values where pH + pOH = 14 at 25°C. pH measures hydrogen ion concentration while pOH measures hydroxide ion concentration.

C. High for acids — This is incorrect. Acids have a low pH (below 7), not a high pH. A high pH value indicates alkalinity or basicity, which is the opposite of acidity.

Explanation:

Correct Answer: (D) Lubricating gels

Astroglide is a personal lubricant gel specifically formulated to reduce friction and relieve dryness, discomfort, and irritation during sexual activity. It does not contain any active pharmacological ingredient intended to treat a medical condition. Its primary function is purely mechanical lubrication, which places it in the category of lubricating gels — preparations designed to reduce friction between surfaces.

Why Other Options are Incorrect:

A. Diagnostic gels — Diagnostic gels such as ultrasound gels are used to facilitate medical imaging by improving sound wave transmission. They serve no lubricating or therapeutic purpose and are unrelated to Astroglide's function.

B. Miscellaneous gels — Miscellaneous gels is a non-specific category that does not accurately describe a product with a well-defined and specific lubricating function like Astroglide.

C. Medicated gels — Medicated gels contain active drug ingredients intended to produce a therapeutic pharmacological effect. Astroglide contains no active drug ingredient and does not treat any medical condition, so it does not qualify as a medicated gel.

Explanation:

Correct Answer: (A) Oleaginous bases

Polyethylene glycol (PEG) bases are water-soluble, synthetic suppository bases that are hydrophilic in nature — meaning they dissolve in body fluids rather than melting at body temperature. They are emphatically not oleaginous (oil-based). Oleaginous bases such as cocoa butter are fatty, water-insoluble materials that melt at body temperature. PEG bases are the opposite — they are water-soluble and dissolve in rectal fluids, which is a fundamentally different mechanism of drug release from oleaginous bases.

Why Other Options are Incorrect:

B. Non-irritating bases — PEG bases are generally considered non-irritating to mucosal membranes when used in appropriate concentrations, making this a true characteristic of PEG suppository bases.

C. Hydrophilic bases — PEG bases are indeed hydrophilic (water-loving) and water-soluble. This is one of their defining and most clinically significant characteristics, distinguishing them from oleaginous bases.

D. Chemically stable — PEG bases are chemically stable, have a long shelf life, and do not require refrigeration, which makes them advantageous over cocoa butter in pharmaceutical manufacturing and storage.

Explanation:

Correct Answer: (A) Oleaginous

Oleaginous (oil-based) formulations such as ointments made with petrolatum or mineral oil are the most effective choice for hydrating dry skin. They work by forming an occlusive barrier on the skin surface that prevents transepidermal water loss (TEWL), trapping moisture within the skin and allowing it to rehydrate. Oleaginous bases have the greatest moisturizing and emollient effect of all topical formulation types, making them the preferred choice for dry skin hydration.

Why Other Options are Incorrect:

B. Foams — Foam formulations are lightweight, spread easily, and are preferred for hairy areas or large body surfaces. They do not provide the occlusive, moisturizing barrier needed to hydrate significantly dry skin.

C. Aerosols — Aerosol formulations deliver drug as a fine spray and evaporate quickly after application. The rapid evaporation actually contributes to skin drying rather than hydration, making them unsuitable for this purpose.

D. Elixirs — Elixirs are oral liquid formulations containing alcohol and water used for systemic drug delivery. They are not topical preparations and are entirely inappropriate for skin hydration.

Explanation:

Correct Answer: (D) 28%

First, calculate the total drug released over 72 hours: 50 μg/hr × 72 hr = 3,600 μg = 3.6 mg released. Next, calculate the drug remaining: 5 mg − 3.6 mg = 1.4 mg remaining. Finally, calculate the percentage remaining: (1.4 mg ÷ 5 mg) × 100 = 28%. Therefore, 28% of the fentanyl remains in the patch when it is removed after 72 hours.

Why Other Options are Incorrect:

A. 68% — This would imply only 1.6 mg was released (32% released), which does not match the calculation of 3.6 mg released at the given rate over 72 hours.

B. 24% — This value is close but incorrect. It may result from a rounding or calculation error in the conversion of micrograms to milligrams.

C. 72% — This incorrectly equates the number of hours worn (72 hours) with the percentage of drug remaining, which is a conceptual error unrelated to the pharmacokinetic calculation.