2 Drug Classes and Schedules

Drug Are Organized in Two Ways Therapeutic classification Pharmacologic classification

Therapeutic Classification of Drugs Based on what the drug does clinically Examples Anticoagulants Antidepressants Antineoplastics

Table 2.1 Therapeutic Classification

Pharmacologic Classification of Drugs Based on the drug's mechanism of action, or how the drug produces its effect At molecular, tissue, or body-system level More specific than therapeutic classification

Table 2.2 Pharmacologic Classification

Examples Calcium-channel blockers Diuretics Adrenergic antagonists

“Prototype” Drug—Serves as Model for a Drug Class Is well understood Has known action and adverse effects Is used to compare other drugs in the same pharmacologic class May not be the most widely used drug in its class Disagreements may exist over which drug should serve as prototype drug.

Newer Drugs in the Same Class Newer drugs in the same class may have replaced the prototype drug's use because they: Are more effective Have a more favorable safety profile Have longer duration of action

Most Drugs Have Three Names Chemical Generic Trade

Drug Has One Chemical Name Assigned using standard nomenclature established by International Union of Pure and Applied Chemistry (IUPAC) Describes physical and chemical properties of drug Sometimes helpful in predicting a substance's physical and chemical properties

Drug Has One Chemical Name Complicated, difficult to remember and pronounce Example: chemical name for diazepam: 7-chloro-1, 3-dihydro-1-methyl-5-phenyl-2H-1, 4-benzodiazepin-2-one

Chemical Group Name Drugs are sometimes classified by a portion of their chemical structure: Cephalosporins, phenothiazines, benzodiazepines Chemical group names can become invaluable to a nursing student.

Generic Name Assigned by the U.S. Adopted Name Council Less complicated and easier to remember

A Drug Has One Generic Name Used by many organizations Food and Drug Administration (FDA) United States Pharmacopoeia World Health Organization Written in lower case Example: diazepam

A Drug Has Several Trade Names Assigned by company marketing the drug Short, easy to remember Also called proprietary, product, or brand name

A Drug Has Several Trade Names Drug developer has exclusive rights to name and market a new drug for 17 years in the United States. Trade name is capitalized. Example: a trade name for diphenhydramine is Benadryl.

Trade Names After 17 years, competing companies may sell a generic equivalent drug, sometimes using a different name, which the FDA must approve.

Trade Names Trade names can be difficult because many drugs contain similar ingredients. A combination drug contains more than one active ingredient. The rule of thumb is that the active ingredients in a drug are described by their generic name, which is lowercase.

Table 2.3 Examples of Brand-Name Products Containing Popular Generic Substances

Rights Issues A pharmaceutical company with exclusive rights to a drug often prices it very high. When rights end, competing companies offer the generic form of the drug for less money.

Rights Issues Depending on the state, a pharmacist may offer the generic form of a prescribed drug, or may only be allowed to dispense the exact form written in the prescription. Drug companies lobby against easy substitution of generic drugs; consumer advocates lobby the opposite.

Generic vs. Brand-Name Drugs It is difficult to tell if there is a difference in effect between two forms of a drug, even if dosage is the same. Inert ingredients may be different.

Generic vs. Brand-Name Drugs Key to comparison is bioavailability—the physiologic ability of the drug to reach its target cells and produce its effect. Measuring how long a drug takes to exert its effect gives a crude measure of bioavailability.

Some States Have a Negative Formulary List List of trade-name drugs that pharmacists may not dispense as generic-drug substitutes Claim that there are differences in bioavailability between generic and trade-name drugs

Addiction and Dependence The overwhelming feeling that drives a person to use a drug repeatedly Dependence A physiologic or psychologic need for a substance

Addiction and Dependence Physical dependence An altered physical condition caused by the adaptation of the nervous system to repeated drug use When the drug is no longer available, the individual expresses physical signs of discomfort known as withdrawal.

Addiction and Dependence Psychologically dependent Little physical discomfort when drug is withdrawn, but intense compelling desire to continue use

Controlled Substances Controlled substances are drugs that: Are restricted by the Controlled Substances Act of 1970 Are frequently abused Have a high potential for addiction or dependence Have restricted use Are placed into one of five schedules

Controlled Substance Act of 1970 Also known as Comprehensive Drug Abuse Prevention and Control Act Restricts use of drugs with potential for abuse Restricted drugs placed into the five schedules Hospitals and pharmacies must maintain complete records of scheduled drugs.

Drug Enforcement Administration (DEA) Regulates Controlled Substance Act Hospitals and pharmacies must register with DEA. Must use assigned registration number to purchase scheduled drugs

Controlled Substances Anyone convicted of unlawful manufacturing, distributing, and dispensing of controlled substances faces severe penalties.

Scheduled Drugs Drugs that have a significant potential for abuse are placed into five categories called schedules. Schedule I drugs have the highest abuse potential, Schedule V the lowest.

Table 2.4 Examples of Brand-Name Products Containing Popular Generic Substances

Schedule I Drugs Restricted to situations of medical necessity, if allowed at all Little or no therapeutic value; mostly used for research

Examples of Schedule I Drugs Heroin LSD Methaqualone

Schedule II-V Drugs May be dispersed only in cases where therapeutic value has been determined Some Schedule V drugs may be dispersed without a prescription.

Not All Drugs with Abuse Potential Are Regulated Tobacco, alcohol, and caffeine

Schedule II Drugs High abuse potential High potential for physical and psychological dependence Therapeutic use with prescription Some drugs no longer used

Schedule II Drugs Have More Restrictions Need special order form to obtain Orders must be written. Orders must be signed by health care provider. Telephone orders to pharmacies are not permitted. No refills are permitted; patient must see health care provider first.

Examples of Schedule II Drugs Morphine PCP Cocaine Methadone Methamphetamine

Schedule III Drugs Moderate abuse potential Moderate physical dependence High potential for psychological dependence Therapeutic use with prescription

Examples of Schedule III Drugs Anabolic steroids Codeine with aspirin or Tylenol Hydrocodone with aspirin or Tylenol Some barbiturates

Schedule IV Drugs Lower abuse potential Lower potential for physical and psychological dependence Therapeutic use with prescription

Examples of Schedule IV Drugs Dextropropoxyphene Pentazocine Meprobamate Diazepam Alprazolam

Schedule V Drugs Lowest abuse potential Lowest physical and psychological dependence Therapeutic use without prescription Examples: OTC cough medicines with codeine

Teratogenic Drug Classification Five categories of risk that a drug poses to a fetus in the case of a pregnant woman taking the drug A, B, C, D, and X

Category A Drugs Controlled studies in women fail to show a risk to the fetus, and the possibility of fetal harm appears unlikely.

Category B Drugs Animal reproduction studies have not shown a fetal risk or adverse effect. Risks have not been confirmed in controlled studies in women.

Category C Drugs Either studies in animals have revealed adverse effects on the fetus and there are no controlled studies in women or studies in women and animals are not available.

Category D Drugs There is confirmation of human fetal risk, but the benefits from use in pregnant women may be acceptable despite the risk—for example, in a life threatening situation.

Category X Drugs Animal and human studies have shown fetal abnormalities. The drug is contraindicated in women who are or may become pregnant.