What factors may influence a patient’s response to medication?

The response to medication can indeed be influenced significantly by a variety of physiological and biological factors, and the correct choice emphasizes the most fundamental ones: age, weight, and existing health conditions.

Age plays a crucial role in pharmacokinetics and pharmacodynamics; for example, infants and the elderly may metabolize drugs differently due to immature or declining organ function, respectively. Weight is equally important as it affects the distribution of drugs within the body — a heavier individual may require a higher dosage to achieve the same therapeutic effect as someone lighter. Existing health conditions can alter the way medications are processed and utilized by the body; for instance, renal or hepatic impairment can lead to decreased clearance of drugs, necessitating careful consideration of dosing and monitoring.

In contrast, while factors such as a patient's mood and environment, medical history and recent surgeries, and allergies and lifestyle choices can also influence medication response, they are often secondary to the fundamental physiological factors of age, weight, and health status. These core biological determinants provide a more direct influence on how medications interact with the body at a systemic level.