Physicochemical properties of drugs

Which of the following best explains why weakly basic drugs are absorbed mainly in the intestine rather than in the stomach?

• They are completely ionized at high pH in the intestine.

• They are unstable in gastric acid.

• They require active transporters found only in the intestine.

• They are mostly unionized at the intestinal pH, enabling passive diffusion.

A drug has a logP value of 6. Which outcome is most likely?

• Rapid renal elimination due to high hydrophilicity.

• Poor absorption due to extreme lipophilicity.

• Easy penetration across the blood-brain barrier with short half-life.

• Optimal distribution due to balanced hydrophilicity and lipophilicity.

Which pair of drugs demonstrates structural non-specificity in their mechanism of action?

• Epinephrine and isoproterenol (acting on adrenergic receptors)

• Codeine and morphine (acting on opioid receptors)

• Sodium sulfate and magnesium sulfate (acting as osmotic laxatives)

• Ibuprofen and naproxen (acting on COX enzymes)

Which of the following compounds would most likely violate Lipinski’s rule for oral bioavailability?

• A drug with molecular weight 420, logP = 4.2, 6 H-bond donors, 8 H-bond acceptors

• A drug with molecular weight 350, logP = 1.5, 3 H-bond donors, 7 H-bond acceptors

• A drug with molecular weight 480, logP = 4.8, 2 H-bond donors, 9 H-bond acceptors

• A drug with molecular weight 290, logP = 2.3, 1 H-bond donor, 5 H-bond acceptors

A weak acid drug with pKa = 4 will be mostly absorbed in which site?

• Mouth (pH 7–8)

• Stomach (pH 1–3)

• Duodenum (pH 6.5–7.5)

• Blood (pH 7.4)

Why would a drug be formulated as a low-soluble salt (e.g., piperazine adipate)?

• To increase water solubility for injections.

• To prolong drug effect by slowing dissolution.

• To improve BBB penetration.

• To reduce drug metabolism in the liver.

Which statement best distinguishes adsorption from absorption?

• Adsorption is the process of drug entry into systemic circulation, while absorption is accumulation on a surface.

• Adsorption is always stronger than absorption due to covalent bonding.

• Adsorption involves accumulation on a surface, while absorption involves passage into the bulk phase.

• Adsorption occurs only with lipophilic drugs, absorption only with hydrophilic drugs.