Pharmacology Essentials: FDA, Naming, and Administration

FDA Regulations and Drug Approval Process

The FDA regulates prescription and OTC drugs, checking for safety and effectiveness. FDA approval for a drug can take up to 17.5 years. The process begins with laboratory and animal studies, followed by preclinical trials, Investigational New Drug (IND) status, Clinical Trials, New Drug Application (NDA), and Phase IV monitoring. The DEA is concerned with illegal drugs or narcotics (controlled substances).

Pharmacokinetics vs. Pharmacodynamics

• Pharmacokinetics: How the body acts upon the drug.
• Pharmacodynamics: How the drug affects your body.

Drug Naming Conventions

• Chemical Name: Describes the specific chemical structure; it is infrequently used (e.g., N-Acetyl-p-aminophenol).
• Generic Name: The official or nonproprietary name assigned by the FDA, derived from the chemical name (e.g., ibuprofen, acetaminophen). All drugs have a generic name, but not every drug is available in generic form.
• Trade Name: Also known as the brand name; it may or may not relate to other names (e.g., Tylenol for acetaminophen, Motrin for ibuprofen).

Drug Classifications

• OTC (Over-the-Counter): Non-prescription drugs used to treat signs and symptoms. Some were once prescription-only, and some exist as both OTC and Rx.
• Prescription (Rx): Used to treat or cure pathology under medical supervision. A physician prescribes and a pharmacist dispenses these, as they carry increased risk.
• Controlled Substances: Scheduled drugs based on increased potential for abuse and dependence, and decreased medicinal use. These require restrictive controls.

Routes of Drug Administration

• Enteral Oral: Systemic dosage forms like pills, syrups, and capsules. Advantages: Easy to administer and inexpensive. Disadvantages: Takes longer for effect and is subject to the first-pass effect (medications are processed by the liver, reducing the final dose reaching the target area).
• Enteral Sublingual/Buccal: Placed under the tongue or in the cheek (e.g., lollipop, film, spray). Advantages: Does not affect the liver; the first-pass effect is not an issue. Disadvantages: Only certain molecules can pass through the cheek.
• Enteral Rectal: Administered via suppository or ointment.
• Parenteral: Dosage via injections or suspensions. Advantages: Quickest to reach the blood; no first-pass effect.
• Inhalation: Dosage via powder or aerosol. Advantages: Goes straight to the lungs to diffuse into the blood.
• Topical: Dosage via creams, patches, or drops. These usually stay local, though some are systemic.

Phases of Pharmacokinetics

1. Absorption: The drug must be bioavailable (the amount in mg remaining after stomach digestion). This is affected by the amount and rate of absorption.
2. Distribution: Can be systemic vs. local. It is affected by uneven distribution, chemical structure, tissue vascularity, and local capillary structure.
3. Duration of Action: The period when concentration levels are sufficient to produce a therapeutic effect.
4. Metabolism: Chemical alteration by enzymes (Substrates + Enzymes = Effects + Metabolites). The liver performs this action, making metabolites water-soluble and inactive (leftovers).
5. Elimination: The removal of drug metabolites via urine or feces. Key organs include the kidneys, sweat glands, and lungs.

The half-life is the time it takes to reduce peak blood concentration by 50%. Patients must take doses more frequently if the half-life is short (e.g., 30 minutes).