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General Principles of Pharmacology

Course Number: 580


Until the nineteenth century, there were few standards or guidelines to protect the public from unsafe and ineffective drug, and unscrupulous purveyors. The first historical milestone in U.S. Food and Drug Laws was the publication of U.S. Pharmacopoeia (USP) in 1820, which listed standards for drug purity and strength, and directions for synthesis.1 Today, this information is found in the U.S. Pharmacopoeia-National Formulary (USP-NF).

To protect the public from deceitful and unsafe practices by manufacturers and clinicians, since the early 1900s, the U.S. Congress enacted a series of drug laws.1,2 The Harrison Narcotic Act of 1914 mandated prescriptions for products containing narcotics. The Durham-Humphrey Amendment of 1951 identified other, i.e., non-narcotic, drugs that cannot be safely used without medical supervision and prohibited their sale without a prescription by a licensed practitioner.

The Controlled Substances Act (CSA) of 1970, collected all legislations related to drugs with abuse potential, placed the drugs in schedules based on their accepted medical use and the potential for dependence when abused, and created a “closed” system for legitimate manufacturing, distribution, and dispensing of such drugs. The current list of controlled substances can be found in the most recent update of Title 21, Section 1308, Code of Federal Regulations.3

In the U. S. there are approximately 500 Food and Drug Administration (FDA)-approved active ingredients, i.e., therapeutic agents, available in several thousand different formulations.4 The FDA has specific requirements on content and format of labeling for human prescription drugs and biological products (Table 1).5 The labeling information must include specific headings and subheadings in a specified order, and must be updated when new information becomes available.

Table 1. Full Content and Format of Labeling for Human Prescription Drug and Biological Products.5

  Warning Box
1 - Indications and Usage
2 - Dosage and Administration
3 - Dosage Forms and Strengths
4 - Contraindications
5 - Warnings and Precautions
6 - Adverse Reactions
7 - Drug Interactions
8 - Use in Specific Populations
    8.1 - Pregnancy
    8.2 - Lactation
    8.3 - Females and males of reproductive  potential
    8.4 - Pediatric use
    8.5 - Geriatric use
9 - Drug Abuse and Dependence
    9.1 - Controlled substance
    9.2 - Abuse
    9.3 - Dependence
10 - Overdose
11 - Description
12 - Clinical Pharmacology
    12.1 - Mechanism of action
    12.2 - Pharmacodynamics
    12.3 - Pharmacokinetics
13 - Nonclinical Toxicology
    13.1 - Carcinogenesis, mutagenesis,
            impairment of fertility
    13.2 - Animal toxicology and/or pharmacology
14 - Clinical Studies
15 - References
16 - How Supplied/Storage and Handling
17 - Patient Counseling Information

The DailyMed website, operated by the U.S. National Library of Medicine, is the official provider of FDA label information.6 It is a trustworthy, standard, comprehensive, up-to-date, look-up and download resource of medication content and other labeling information found in package inserts of drugs marketed in the United States. The labeling information is the most recent submitted to and approved by the FDA and includes strengthened warnings undergoing FDA review.

Clinicians and patients acknowledge the major role played by drugs in modern healthcare. However, it is also of note that therapeutic agents seldom exert their beneficial effects without also causing adverse drug effects (ADEs). ADEs range from mild to severe reactions and can lead to hospitalization, permanent disability, and even death. The inevitability of this therapeutic dilemma lends credence to the statement that there are no “absolutely” safe biologically active agents.

Hence, it is important for practitioners to have a solid foundation in pharmacology. Understanding how drugs affect physiological homeostatic mechanisms at the molecular level forms the basis for developing sound therapeutic strategies. Consequently, the use of therapeutic agents requires an understanding of basic pharmacological principles. These principles apply to all drugs and are predicated on pharmacodynamic mechanisms and pharmacokinetic processes.