FACTORS AFFECTING MEDICATION DOSAGES AND RESPONSES

Body weight: Because body tissues absorb medications, individuals who have a greater body mass require larger doses. Because the percentage of body fat an individual has can alter the distribution of a medication, basing dosages on body surface area can be a more precise method of regulating an individual’s response to a medication.

Age: Young children who have immature liver and kidney function, and older adults, often with reduced liver and kidney function, require proportionately smaller medication doses to compensate for their heightened sensitivities to medications.

Gender: Women respond differently to medications than men due to a higher proportion of body fat and the effects of female hormones.

Genetics: Genetic factors such as missing enzymes can alter the metabolism of certain medications, thus enhancing or reducing a medication’s action. The usual effect is either fewer benefits from the medication or greater medication toxicity.

Biorhythmic cycles: Responses to some medications vary with the biologic rhythms of the body. For example, hypnotic medications work better when given at the usual sleep time than at other times.

Tolerance ● Reduced responsiveness to a medication clients take

over time, such as morphine, is pharmacodynamic tolerance. Other medications, such as barbiturates, cause metabolic tolerance as metabolism of the medication increases over time and the effectiveness of the medication declines.

● Some clients develop cross‑tolerance to another medication after they have become tolerant to a chemically similar medication.