a drug-to-drug interaction, individuals should also let their doctor know if they are taking drugs prescribed by other physicians. Individuals should closely follow instructions for use and package directions on both prescription and over-the-counter drugs. Consulting with a pharmacist and/or physician may be beneficial if package directions are unclear to the patient. In general, grapefruit juice should not be taken with medication unless recommended by a doctor. Patients taking MAOI inhibitors should always check food and beverage labels to ensure tyramines aren’t included and should avoid all fermented drinks. or antagonists. Genetic factors can also play a role in changing the number or function of specific receptors. 4. The largest and most important set of mechanisms that causes variation in responsiveness to a drug is associated with changes in post receptor processes; that is, events that occur after the drug binds to receptors, involving biochemical processes in the responding cell and organ systems in the body with which it interacts. Before administering treatment, the prescriber must be aware of any individual characteristics that might influence the drug’s effects. The most important of these are the age and health of the patient, as well as the degree or severity of the individual’s physical impairment by disease or condition. To avoid toxicity, drugs are typically administered in the lowest dosage that brings about the desired benefit and in conjunction with other drugs that limit the toxicity of the first drug. In addition, specific drug actions may be increased by adjusting the concentration of drug available to receptors in different parts of the body by administering the drug by a different route – as an inhalant, for example, instead of a pill. These factors are typically incorporated into client assessment when prescribing specific drugs: ● Age : Very young and elderly individuals have a limited ability to metabolize and excrete drugs. In neonatal cases, hepatic enzyme systems are not fully functioning, so drug metabolism is reduced and there is increased risk of toxicity. In the elderly, there is a longer period of metabolism by the liver and a decline in renal function, which may produce a situation of delayed excretion by the kidneys and a prolonged drug action. ● Body weight : Body size affects the amount of drug distributed and available. This is the reason many drugs are prescribed according to body weight, especially for long-term treatment. ● Nutritional level : Malnourishment alters drug distribution and metabolism. Poor diets may slow enzyme activity, which delays the drug’s metabolism. Reduction in plasma protein, (i.e., a low-protein diet) may alter drug availability. ● Food/drug interactions : Food may enhance or inhibit drug absorption. ● Diseases : Diseases like Crohn’s disease, renal disease or liver disease (hepatitis, cirrhosis, liver failure) may affect absorption. Circulatory diseases, including heart failure and peripheral vascular disease, reduce distribution and transportation of drugs throughout the body. ● Genetic/ethnic factors : Good or poor enzymatic function can be inherited. ● Pregnancy and lactation : Both may affect drug absorption and distribution.
who take a number of medications or self-treat with over- the-counter drugs and/or herbal remedies may not be able to determine which drug actually triggered the interaction. A 2017 study found that 35 percent of respondents participating disclosed their use of herbal supplements to their health care providers (Rashrash, 2017). In cases where a serious drug or herb interaction occurs, withholding this information can delay diagnosis and put the patient at increased risk. Patients with chronic health conditions, particularly those with liver disorders, should always inform their health care professional before taking any over-the-counter medications or dietary supplements. Because of the risk for Human variation to drug responsiveness Humans vary considerably in the degree to which they respond to drugs. One individual may even respond differently to the same drug at different points in time. In some cases, an individual will respond in an unusual or idiosyncratic way. These effects may be associated with genetic differences in how the body processes the drug or, in some cases, immunologic mechanisms, known as allergic reactions . In such cases, the individual is considered hypersensitive to the drug. There are also individuals who react much less (hyporeactive) or more intensely (hyperreactive) than the vast majority of those given the same dose. In some cases, the degree of response changes during the course of treatment. Usually, if the individual’s response changes over the course of administration, it is a decrease in effect, called a tolerance , to the drug. When responsiveness decreases rapidly after administration of the drug, the response is referred to as tachyphylaxis . When administering a drug for the first time, the prescriber must consider a number of factors, including the potential of a particular drug to produce tolerance or tachyphylaxis, as well as the individual’s age, gender, body size, health, genetic factors and other drugs the individual is taking. Four main properties are associated with variation in drug responsiveness among different individuals or within a particular individual at different points in time: 1. Changes in the concentration of a drug that reaches a receptor: Pharmacokinetic differences, including differences in absorption rate of a drug, how the drug is distributed through different compartments of the body, and/or differences in eliminating the drug from the blood. Changes in the concentration will alter what receptors it reaches, changing the drug’s effects. While many differences can be anticipated according to characteristics like age, weight, health and function of the liver and kidneys, for example, specials tests must be administered to confirm the presence of different drug- metabolizing enzymes or other genetic differences. 2. Variation in the concentration of an endogenous receptor ligand is associated specifically with variability in responses to drug antagonists. Partial agonists may exhibit even more extreme responses. 3. Changes in the number or function of receptors: Studies show that changes in drug responsiveness may be caused by increases or decreases in the number of receptor sites or by changes in the efficiency in the coupling of receptors. In some cases, the change in the number of receptors involved is brought about by hormones; in other cases, the agonist ligand itself causes a decrease in the number of receptor sites involved or the coupling efficiency (desensitization) of its receptors. These properties may contribute to tachyphylaxis, or tolerance to the drug, and can occur with either agonists
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