5 Pharmacology Practice Questions and Explanations
Learn how absorption, distribution, metabolism, excretion, and drug action shape medication effects, interactions, safety, and individual response.
How the body handles drugs
describes how the body handles a drug through absorption, distribution, metabolism, and excretion. Together, these processes shape drug exposure, effects, timing, and safety.
Absorption and first-pass metabolism
After an oral medication is absorbed, it may pass through the intestine and liver before reaching the general circulation. The occurs when some of the drug is metabolized along this route, reducing the amount of unchanged drug that reaches circulation. The effect varies by medication and route; it does not mean that every oral drug is inactivated.
Distribution and
Many drugs circulate partly bound to plasma proteins, including albumin, and partly unbound. The is generally more available to reach tissues and interact with targets immediately, while bound drug may act as a temporary reservoir. Changes in can affect exposure, but the clinical effect depends on the drug and the person’s overall physiology.
Metabolism and drug interactions
Metabolism breaks down drugs, and the activity of a drug-metabolizing enzyme can affect how much of a drug remains in the body. If another drug inhibits an enzyme that mainly breaks down a medication, the medication’s concentration or exposure may increase, potentially raising the risk of adverse effects. Enzyme induction can instead increase metabolism and potentially reduce exposure. The direction and clinical importance of an interaction depend on the specific drugs.
Excretion and kidney function
The kidneys are a major route of excretion for many drugs and their metabolites. When kidney function declines, may be reduced, slowing elimination and potentially causing a drug to accumulate, prolonging exposure and raising the risk of adverse effects. Whether a dose needs adjustment is specific to the medication and the patient; a clinician should assess it.
How drugs act on the body
concerns how a drug acts on the body. An binds to and activates a receptor, producing a response. An binds in a way that blocks or reduces activation by an .
Benefits and unwanted effects
A is the intended beneficial response to a medication, such as the intended reduction of a patient’s pain. An unwanted response may be described as a side effect or, when harmful or clinically significant, an . Unwanted effects can occur even when a medication is used as directed.
The
The lies between exposures that are too low to provide adequate benefit and exposures that may be toxic. When a medication has a narrow , the effective and potentially harmful exposure ranges are relatively close. Relatively small changes in dose or drug concentration can matter, and monitoring may be appropriate for particular medications.
Why responses vary
Two people who receive the same prescribed dose may respond differently. Differences can involve , such as altered metabolism or excretion, and , such as sensitivity at the drug’s target.
Factors influencing response
Factors that can contribute to variation in medication response include age, kidney or liver function, genetics, other medications or interacting substances, and whether doses are taken as prescribed. Genetic information is only one part of the overall assessment.