Chapter 1: Orientation to Pharmacology

Chapter 1: Orientation to Pharmacology This introduction to pharmacology defines key terms such as drug, pharmacology, clinical pharmacology, and therapeutics. It explains that pharmacology is the study of drugs and their interactions with living organisms, while clinical pharmacology focuses on the study of drugs in humans. The text also discusses the importance of understanding how drugs produce their therapeutic effects and the factors that determine the intensity of drug responses. Bullet points Four Basic Terms ● ● ● ● A drug is any chemical that can affect living processes Pharmacology is the study of drugs and their interactions with living systems Clinical pharmacology is the study of drugs in humans, including patients and healthy volunteers Therapeutics (or pharmacotherapeutics) is the use of drugs to diagnose, prevent, or treat disease Scope of the Text ● ● ● This text will focus primarily on drugs with therapeutic applications It will cover clinically relevant information in pharmacology and clinical pharmacology It will not address all compounds that fit the definition of a drug Pharmacology as a Science ● ● Pharmacology draws on information from multiple disciplines such as anatomy, physiology, chemistry, microbiology, and psychology It encompasses the study of physical and chemical properties of drugs, as well as their biochemical and physiological effects Therapeutics and its Concerns ● ● Therapeutics focuses on the use of drugs to diagnose, prevent, or treat disease, and the medical use of drugs This text mainly emphasizes the basic science underlying the clinical use of drugs Risks and Benefits of Drugs ● ● Drugs have both therapeutic and adverse effects The Greek word for drug, "pharmakon," can be translated as both remedy and poison Drug Selectivity ● A selective drug is defined as one that affects specific targets or tissues Properties of an Ideal Drug: ● ● ● ● ● ● ● Reversible Action: Most drug effects should subside within an appropriate time Predictability: Knowing how a patient will respond to a drug before administration Effectiveness: A drug should elicit the intended responses Safety: A drug should not produce harmful effects, even at high doses and for a long time Selectivity: A drug should target the intended sites without causing widespread effects Ease of Administration: The drug should be simple to administer and have a convenient dosage schedule Freedom from Drug Interactions: Minimizing the risk of harmful interactions with other drugs Drug Interactions ● ● When a patient is taking two or more drugs, drug interactions may occur Interactions can either augment or reduce drug responses ● ● Examples: respiratory depression caused by the combination of diazepam (Valium) and alcohol Antibacterial effects of tetracycline can be reduced by taking it with iron or calcium supplements Importance of Considering Drug Interactions ● ● ● When a patient is taking multiple medications, the possible impact of drug interactions must be considered Drug interactions can have significant effects on therapeutic outcomes and patient safety Aspirin and related drugs can cause life-threatening gastric ulceration, perforation, and bleeding when taken long-term in high doses Cost of Medications ● ● ● ● The cost of drugs can be a substantial financial burden for patients Expensive medications can limit access to necessary treatment Example: adalimumab (Humira) for rheumatoid arthritis and Crohn disease can cost more than $112,000 per year Chronic conditions requiring daily medication can lead to cumulative expenses Chemical Stability of Drugs ● ● ● Some drugs may lose effectiveness during storage or when prepared for administration Chemical instability can result in the loss of drug efficacy Certain drugs require periodic discarding due to chemical instability Generic Names of Drugs ● Generic names of drugs are often complex and difficult to remember and pronounce ● ● ● Brand names for drugs are usually simpler and easier to remember Examples: acetaminophen (Tylenol), ciprofloxacin (Cipro), simvastatin (Zocor) An ideal drug would have a simple generic name that is easy to recall and pronounce Factors Influencing Drug Responses ● ● ● Multiple factors determine how an individual will respond to a drug Understanding these factors helps in predicting and explaining drug effects The concentration of the drug at its sites of action determines the intensity of the drug response Factors affecting drug responses ● ● ● ● The primary determinant of drug concentration is the administered dose Administered dose is the same as the prescribed dose when administered correctly The intensity of drug response depends on the steps leading from the prescribed dose to the concentration Medication errors, administration, patient adherence, absorption, distribution, metabolism, excretion, physiologic and pathologic variables, genetic variables, and drug-receptor interaction affect drug concentration and response Pharmacodynamics ● ● ● ● Pharmacodynamics is the impact of drugs on the body The initial step leading to a response is the binding of a drug to its receptor The drug-receptor interaction is followed by a sequence of events resulting in a response The patient's functional state and placebo effects influence drug responses Administration and medication errors ● ● ● Drug dosage, route, and timing of administration are important determinants of drug responses Poor adherence to medication can result in incorrect administration and affect drug response Medication errors made by healthcare staff can detract from achieving the therapeutic objective Sources of individual variation ● ● ● ● Physiologic variables, pathologic variables, and genetic variables contribute to individual variation in drug response Physiologic variables include age, gender, and weight Pathologic variables include kidney and liver function Genetic factors can alter drug metabolism and predispose patients to unique drug reactions Pharmacokinetics ● ● ● Pharmacokinetic processes determine drug concentration at sites of action The four major pharmacokinetic processes are absorption, distribution, metabolism, and excretion These processes collectively impact how the body handles drugs Properties of an ideal drug ● The most important properties of an ideal drug are effectiveness, safety, and selectivity Individualized drug therapy ● Because all patients are unique, drug therapy must be tailored to each individual Benefits and risks of drugs ● ● ● Drugs have both benefits and risks If a drug is not effective, it should not be used There is no such thing as a wholly selective drug; all drugs can cause side effects Objective of drug therapy ● The objective of drug therapy is to provide maximum benefit with minimum harm