• Portage Learning PHARMACOLO NURS 251 Module 1

• Portage Learning PHARMACOLO NURS 251 Module 1 1.1 : An Introduction to Pharmacology Concepts Pharmacology is the study or science of drugs. What is a drug? A drug is any chemical that affects the physiologic processes of a living organism. Commonly, the term drug refers to any medication that is used for diagnosing, curing, or treating disease. Drug Effects Drugs have many different effects on the body including the following: (1) therapeutic effects, (2) side effects, (3) adverse effects, and (4) toxic effects. Therapeutic effect is the desired drug effect to alleviate some condition or symptom. Side effects are the drug effect other than the therapeutic effect that are usually undesirable but not harmful. Adverse effect is a general term for undesirable and potentially harmful drug effects. Toxic effects are undesirable drug effects that implies the drug is poisoning the body and can be harmful or even life- threatening. Clinically, it is important to recognize the difference between these different ways drugs can affect the body. A simple side effect could be something as harmless as mild nausea after taking a medication that can be managed by taking it with food. The drug therapy can continue without a problem. However, adverse effects need to be assessed to determine whether there is any risk of harm. Drug therapy is often a risk vs. benefit assessment. The patient’s provider should weigh the risk of taking the medication vs. the benefit. It often comes down to the severity of the disease being treated to decide the number of adverse events that will be tolerated. A good example of this is chemotherapy treatments for cancer. There are often adverse events associated with these treatment regimens, yet the treatment is continued because the benefit of treating the cancer is greater than the adverse events the patient experiences. However, there are certainly times when a treatment becomes too toxic, and the patient is unable to tolerate the regimen. This is often a large part of managing a cancer patient’s treatment, to assess how they are handling the adverse effects associated with the treatment regimen and determine whether it is becoming too toxic and needs to be suspended. Basic Concepts There are some basic concepts that are important to understand and that can be applied to any drug. Most important is the drug’s mechanism of action—how a drug produces its effects. This course will cover the accepted mechanism of action of known drugs. When a drug enters the body, it has a targeted site of action—the location within the body where a drug exerts its therapeutic effect, often a specific drug receptor. Generally, these sites of action or receptors are on the surface or inside a cell. Receptors are specific cellular structures that a drug binds to in order to produce a physiologic effect. When a drug binds to a receptor, it can act either as an agonist, works to activate a physiologic response or drug effect, or an antagonist, works to interfere with other drugs or substances from producing a drug-effect. The dose-dependent relationship is a basic principle of pharmacology which states that the response to any drug depends on the amount of drug given. This is referred to as the dose dependent relationship. A dose is the exact amount of drug that is given. As shown in Figure 1.1, the onset of action is the time from the drug administration to the first observable effect. The duration of action is the length of time that the drug continues to produce its effect. All drugs have a therapeutic range defined as when the drug concentration is above the minimum effective concentration and below the maximum tolerate concentration.