Pharmacology basics

• Pharmacology is a science drawing on information from 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, is the use of drugs to diagnose, prevent, or treat disease, or to prevent pregnancy.

Ideal Drug Properties

• Effectiveness is the most important property a drug can have.
• Safety means the drug cannot produce harmful effects.
• Selectivity means the drug elicits only the response for which it is given.

Additional Ideal Drug Properties

• Reversible action is an additional property.
• Predictability is an additional property.
• Ease of administration is an additional property.
• Freedom from drug interactions is an additional property.
• Low cost is an additional property.
• Chemical stability is an additional property.
• A simple generic name is an additional property.
• No drug is ideal.

Adverse Effects Examples

• Certain anticancer drugs like cyclophosphamide and methotrexate can increase the risk for infection.
• High doses of opioid analgesics can cause respiratory depression for example morphine or meperidine.
• Aspirin and related drugs can cause severe gastric ulceration, perforation, and bleeding when taken for prolonged periods.

Factors Determining Drug Response

• Administration affects drug response intensity.
• Pharmacokinetics affects drug response intensity.
• Pharmacodynamics affects drug response intensity.
• Sources of individual variation affect drug response intensity.

Administration

• Dosage size, route, and timing are important determinants of drug responses.
• Medication errors affect drug response.
• Patient adherence affects drug response.

Pharmacokinetics

• Pharmacokinetics affect how much of the administered dose gets to its sites of action.
• Pharmacokinetics describe the impact of the body on drugs.
• The four major pharmacokinetic processes are drug absorption, distribution, metabolism, and excretion.

Pharmacodynamics

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

Individual Variation Sources

• Physiologic variables like age, gender, and weight are sources of individual variation.
• Pathologic variables like diminished kidney and liver function are sources of individual variation.
• Genetic variables can alter drug metabolism and predispose patients to unique interactions.
• Drug interactions are sources of individual variation.

New Drug Development

• New drug development uses randomized controlled trials.
  • These trials use controls
  • These trials randomize
  • These trials are blind

Drug Development Stages

• Preclinical testing is part of drug development.
• Clinical testing is part of drug development.
  • This involves Phase I
  • This involves Phases II and III
  • This involves Phase IV: Postmarketing surveillance

Testing Procedure Limitations

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

Exercising Discretion with New Drugs

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

Drug Names

• Drugs have chemical, generic, and trade names.

Generic vs. Trade Names

• Generic products should be therapeutically equivalent to brand-name products.
• Differences between brand-name and generic products may justify using 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 administered doses.
• 40% of Americans take at least one OTC drug every two days.
• Four times as many illnesses are treated by a consumer using OTC drugs compared to consumers visiting a physician.

Drug Information Sources

• Clinicians
• Pharmacists
• Poison control centers
• Pharmaceutical sales representatives can supply drug information.
• Reference books can provide drug information.
  • For example, Goodman & Gilman's The Pharmacological Basis of Therapeutics
  • For example, Pharmacotherapy: A Pathophysiologic Approach
  • For example, Applied Therapeutics: The Clinical Use of Drugs