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Pharmacology for Nurses

1.3 Drug Classifications and Prototypes

Pharmacology for Nurses1.3 Drug Classifications and Prototypes

Learning Outcomes

By the end of this section, you should be able to:

  • 1.3.1 Explain the basis for placing drugs into therapeutic and pharmacologic classes.
  • 1.3.2 Discuss the prototype approach to drug classification.
  • 1.3.3 Define federal controls on drugs that have abuse potential.

Drug Classifications

One helpful method for sorting out the sheer number of drugs on the market is by organizing them into different classifications. Most drugs are classified in two ways—therapeutic classification and pharmacologic classification.

  • Therapeutic classification refers to a drug’s therapeutic use or clinical indication (the diagnosis or disease being treated). When using a therapeutic classification, one describes the therapeutic effect, or the clinical result that occurs after the client takes a drug. For example, in Antihypertensive and Antianginal Drugs, the drug metoprolol is discussed. Its therapeutic classification is antianginal because it relieves the chest discomfort associated with coronary artery disease. It also reduces blood pressure, so it has a second therapeutic classification and is also known as an antihypertensive.
  • Pharmacologic classification refers to how the drug works in the body—its mechanism of action. Metoprolol’s pharmacologic classification is beta-adrenergic blocker—it works by blocking the stimulation of the body’s beta-adrenergic receptors, which inhibits the heart’s response to sympathetic nerve stimulation. Sometimes a drug is classified by the body system it affects, such as the autonomic nervous or upper respiratory systems.

Important note: Even though a drug may have more than one therapeutic classification, such as the previous example of metoprolol being both an antianginal and an antihypertensive, it will essentially have the same mechanism of action (though its targeted effect may be different), side effects, and safety parameters. Knowledge of a drug’s classification helps the nurse understand its intended effects and its adverse effects. The primary difference is in the client’s reason for taking the drug.

Drug Prototypes

Once drugs are sorted into classifications, it is customary to utilize one drug within the class to compare to all the other drugs within that class. It becomes the “class representative,” known as the drug prototype. Using a drug prototype is helpful for an individual learning pharmacology because it makes learning much more manageable. It is also helpful in the clinical setting. Consider the situation of a nurse who has administered the beta-adrenergic blocker metoprolol multiple times in the clinical setting and is quite familiar with its actions and side effects. When a health care provider orders the beta-adrenergic blocker atenolol, that nurse knows it will have a similar mechanism of action, side effects, and safety parameters as metoprolol. This is much easier for the student to learn than attempting to identify and learn every single drug made in the class.

Pharmacology books often use drug prototypes to simplify explanations of drug classes and assist students in their learning. Table 1.3 provides an example of a drug prototype table used throughout this text.

Drug Class
Pharmacological class or Therapeutic class

Mechanism of Action
This is a description of how the drug works in the body.
Drug Dosage
This indicates the quantity, frequency, and route of administering the medication to the client, and how it may differ by age, body weight, or clinical condition.
How is the drug used?
What disease or symptom does it treat?
Is it used for prevention?

Therapeutic Effects
This explains the drug’s desired effects—how the provider knows if it is effective.
Drug Interactions
Are there any drugs that cause undesired effects if used together?

Food Interactions
Do foods prevent the desired effect from occurring? Do certain foods cause toxicity?
Adverse Effects
What undesired effects might occur?
Is there a reason this drug should be avoided in this client?
Table 1.3 Sample Drug Prototype Table

Drug Schedules

Many different chemicals, substances, and drugs come under U.S. Drug Enforcement Administration (DEA) oversight (U.S. DEA, n.d.). In 1970, Congress passed the Controlled Substances Act, which led to the establishment of the DEA in 1973 and described the controls for manufacturing, distributing, and prescribing habit-forming drugs. This legislation not only categorized controlled substances based on their potential for abuse but also established drug schedules and provided drug treatment programs for those with addictions. All hospitals and pharmacies must keep records of drugs purchased and sold. Any health care provider with prescriptive authority must be registered with the DEA and given a unique DEA identifier that they must place on any controlled substance prescription.

As noted in Table 1.4, Schedule I drugs have no medical use and a very high potential for abuse and physical/psychological dependency; therefore, most health care providers cannot issue prescriptions for those drugs, and pharmacies cannot fill those prescriptions. If research is being conducted with a Schedule I drug, applications and supporting documents have to be sent to the DEA for special permission. Schedule II, III, and IV drugs must have a medically sound reason for a prescription. Schedule V drugs are those with the lowest potential for misuse and dependency (U.S. DEA, n.d.).

Cannabis has been classified as a Schedule 1 drug since the 1970 Controlled Substances Act. However, more than half of the states in the nation have decriminalized the substance, with some permitting medical usage and others both medical and recreational usage. As of May 2024, the Drug Enforcement Agency has recommended that cannabis be reclassified as a Schedule III drug, which would support wider medical usage and scientific research but not permit recreational usage on a national level. Formal reclassification will require additional steps.

Drug Schedule Examples of Drugs in This Category Therapeutic Use Potential to Cause Physical or Psychological Dependency Potential for Abuse
Schedule I Heroin, lysergic acid diethylamide (LSD), peyote; see above regarding cannabis No accepted medical use High The highest potential for abuse
Schedule II Cocaine, methamphetamine, oxycodone, fentanyl, methadone, hydromorphone, mixed amphetamine salts, Adderall, Ritalin Medical use High High
Schedule III Acetaminophen with codeine, ketamine, anabolic steroids Medical use Moderate to Low Moderate to Low
Schedule IV Benzodiazepines such as alprazolam and diazepam; tramadol Less abuse potential than Schedule III drugs and limited dependence liability Low Low
Schedule V Atropine with diphenoxylate (Lomotil), pregabalin General medical use Low Low
Table 1.4 Scheduled Drugs in the United States (sources:;

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