Pharmacology: Basic Terms and Drug Properties

• "First do no harm" and "Honor the healing power of nature" are concepts attributed to Hippocrates.
• "It depends only upon the dose, whether a poison is poison or not… a lot kills, a little cures" - Paracelsus.

Pharmacology

• Pharmacology is a science drawing on information from multiple disciplines.
• These disciplines include anatomy, physiology, psychology, chemistry, and microbiology.

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.
• Therapeutics, also known as pharmacotherapeutics, involves the use of drugs to diagnose, prevent, or treat disease or to prevent pregnancy.

Properties of an Ideal Drug

• Effectiveness is considered the most important property a drug can possess.
• A safe drug will not produce harmful effects.
• A selective drug elicits only the response for which it is given.

Examples of Adverse Effects

• Certain anticancer drugs can increase the risk for infection; cyclophosphamide and methotrexate are examples.
• Opioid analgesics at high doses can cause respiratory depression; morphine and meperidine are examples.
• Aspirin and other related drugs can cause severe gastric ulceration, perforation, and bleeding when taken for prolonged periods.

Additional Properties of an Ideal Drug

• Reversible action.
• Predictability.
• Ease of administration.
• Freedom from drug interactions.
• Low cost.
• Chemical stability.
• Simple generic name.
• No drug is ideal.

Factors Determining Drug Response Intensity

• Administration.
• Pharmacokinetics.
• Pharmacodynamics.
• Sources of individual variation.

Administration

• Important determinants of drug responses are dosage size, route, and timing.
• Medication errors.
• Patient adherence.

Pharmacokinetics

• Determines how much of the administered dose reaches its sites of action.
• It's the impact of the body on drugs
• Four major pharmacokinetic processes: drug absorption, drug distribution, drug metabolism, and drug excretion.

Pharmacodynamics

• The impact of drugs on the body.
• Drug-receptor interaction involves the binding of a drug to its receptor.
• Patient's functional state influences pharmacodynamic processes.
• Placebo effects help determine the responses a drug elicits.

Sources of Individual Variation

• Physiologic variables like age, gender, and weight.
• Pathologic variables, such as diminished function of kidneys and liver.
• Genetic variables can alter the metabolism of drugs and predispose the patient to unique interactions.
• Drug interactions.

New Drug Development

• The randomized controlled trial is used.
• The randomized controlled trial makes use of controls.
• Randomization is used.
• Blinding is part of the process.

Stages of New Drug Development

• Preclinical testing.
• Clinical testing includes Phase I, Phases II and III, and Phase IV: Postmarketing surveillance.

Limitations of the Testing Procedure

• There is limited information about women and children.
• Failure to detect all adverse effects is a limitation.

New Drugs and Discretion

• Avoid immediately adopting new drugs or being the last to abandon older ones.
• Balance potential benefits against inherent risks.
• New drugs generally present greater risks than old ones.

Drug Names

• Chemical name.
• Generic name.
• Trade name.

Generic vs Trade Names

• Consider whether generic products and brand-name products are therapeutically equivalent.
• Consider whether a difference between brand-name and generic products justifies the use of trade names.

Over-the-Counter Drugs

• Americans spend about $20 billion annually on over-the-counter (OTC) drugs.
• OTC drugs account for 60% of all doses administered.
• Forty percent of Americans take at least one OTC drug every 2 days.
• Four times as many illnesses are treated by a consumer using an OTC drug as by a consumer visiting a physician.

Sources of Drug Information

• People such as clinicians, pharmacists, and poison control centers.
• Pharmaceutical sales representatives.
• Reference books like Goodman & Gilman’s The Pharmacological Basis of Therapeutics, Pharmacotherapy: A Pathophysiologic Approach, and Applied Therapeutics: The Clinical Use of Drugs.