How Medications are Developed
How Medications Work
Principles of Medication Safety
Spring 2026
Drug Regulation
• Federal Drug
Administration (FDA)
⚬ Oversees drug
testing to ensure
safety and
efficacy of all
drugs
Hazardous Drug Identification
• Determined by the NIOSH
• Necessary to exercise the proper drug handling precautions to avoid:
⚬ Carcinogenicity
⚬ Teratogenicity or developmental toxicity
⚬ Reproductive toxicity
⚬ Organ toxicity at low doses
⚬ Genotoxicity
• Drug handling precautions may include one or more of the following:
⚬ Use of double chemotherapy gloves
⚬ Use of protective eyewear
⚬ Use of a protective gown
⚬ Reparatory protection
⚬ Ventilated engineering control
Drug Names
• Chemical Name
⚬ N-Acetyl-para-aminophenol
• Generic Name
⚬ Acetaminophen
• Brand Name
⚬ Tylenol, Excedrin
Over the Counter (OTC) Drugs
• No prescription needed in the United States
• 40% of Americans take at least one OTC medication every 2 days
• Some medications that were originally sold only via prescription are now OTC
• Since 2006, new labeling requirements by FDA
• Increased availability increases the risk for drug interactions and drug-induced
health problems (e.g. sedation)
How Medications Work
How Drugs Cross a Cell Membrane
• Channels and Pores
• Transport Systems
• Direct Penetration of the
Membrane
⚬ Most Common
Drug Absorption
• Dependent on:
⚬ Rate of Dissolution
⚬ Surface Area
⚬ Blood Flow
⚬ Lipid Solubility
⚬ pH Partitioning
Administration Routes
Parenteral
• Intravenous (IV)
⚬ No barriers to absorption, absorbed quickly, rapid onset, permits large fluid
volumes, irritant drugs
• Intramuscular (IM)
⚬ Easily passes through capillary wall, rapid to slow absorption, permits use of
poorly soluble drugs
• Subcutaneous (SubQ)
⚬ Same considerations for IM injections
Enteral
• Oral (PO)
⚬ Absorbed through the capillary wall of the epithelial lining of the GI tract, slow
and variable absorption, easy, convenient, ideal for self-medication, inexpensive
⚬ In terms of variability, consider tablets, enteric coated preparations and
sustained-release preparations
Other Routes: Transdermal, Vaginal, Rectal, Inhalation, Topical
Distribution
• Drug is delivered by the
blood to the tissues and
organs of the body
• Rate of flow is determined
by blood flow to that tissue
Distribution
• The Blood-Brain Barrier
⚬ Tight junctions that make it difficult for
drugs to pass through
⚬ Only drugs that are lipid soluble or have a
transport system can cross to a significant
degree
• Placental Drug Transfer
⚬ Membranes of the placenta do not
constitute an absolute barrier to the
passage of drugs
Distribution
• Drugs can form
reversible bonds with
various proteins
• Plasma albumin is the
most abundant and
important protein
⚬ Large molecule that always
remains in the bloodstream
⚬ Impacts drug distribution
Entering Cells
• Some drugs must enter cells to reach the site of action
• Most drugs must enter cells to undergo metabolism and excretion
• Many drugs produce their effects by binding with receptors on the external
surface of the cell membrane
⚬ These do not need to cross the cell membrane to act
Metabolism
• Also known as biotransformation
• Defined as the chemical alteration of drug structure
• Most often takes place in the liver
• Hepatic drug-metabolizing enzymes
• Therapeutic consequences of drug metabolism
• Special considerations in drug metabolism
• Most drug metabolism that takes place in the liver is performed by the hepatic
microsomal enzyme system, which is also known as the P450 system
Therapeutic Consequences of Drug
Metabolism
• Accelerated renal drug excretion
• Drug inactivation
• Increased therapeutic action
• Activation of prodrugs
• Increased or decreased toxicity
Special Considerations in Drug Metabolism
• Age
• Induction of drug-metabolizing enzymes
• First-pass effect
• Nutritional status
• Competition among drugs
Excretion
Drug Responses
• Minimum Effective Concentration
• Toxic Concentration
• Therapeutic Range
• Drug Half-Life
• Plateau
Pharmacodynamics
• Maximal Efficacy
• Relative Potency
• Receptor
• Affinity
• Agonist
• Antagonist
⚬ Noncompetitive and Competitive
• Partial Agonist
• Therapeutic Index
Drug Interactions
• Intensification of effects
⚬ Increased therapeutic effects
⚬ Increased adverse effects
• Reduction of effects
⚬ Reduced therapeutic effects
⚬ Reduced adverse effects
• Creation of a unique response
• Consider interactions with food as well
⚬ Grapefruit juice
Minimizing Adverse Drug Interactions
• Minimize the number of drugs a patient receives
• Take a thorough drug history
• Be aware of the possibility of illicit drug use
• Adjust the dosage when metabolizing inducers are added or deleted
• Adjust the timing of administration to minimize interference with absorption
• Monitor the patient for early signs of toxicity
• Be especially vigilant when a patient is taking a drug with a low therapeutic index
Adverse Drug Reactions
• Side Effect
• Toxicity
⚬ Hepatotoxicity, cardiotoxicity, nephrotoxicity
• Allergic Reaction
• Idiosyncratic Effect
• Paradoxical Effect
• Iatrogenic Disease
• Physical Dependence
• Carcinogenic Effect
• Teratogenic Effect
Medication Errors
• Cause injury to up to 1.3 million people per year
• 13 major categories including wrong: patient, drug, route, time, dose, omitted dose,
wrong dosage form, wrong diluent, wrong strength/concentration, wrong infusion
rate, wrong technique, deteriorated drug error, wrong duration of treatment
• Caused by human factors, communication mistakes and name confusion
Medication Reconciliation
• A process designed to reduce medication omissions, duplications
and dosing errors as well as adverse drug events and
interactions
• Five steps:
1. Create a list of current medications
2. Create a list of all medications to be prescribed in the new setting
3. Compare the medications on both lists
4. Adjust medications based on the comparison
5. During next transition of care, provide new list to patient and new provider
• Should be conducted during every transition of care
Variation in Drug Responses
• Body weight
• Age
• Kidney and liver disease
• Acid-base imbalance
• Altered electrolyte status
• Tolerance
• Placebo Effect
• Bioavailability
• Sex and ancestry
• Co-morbidities
• Diet
• Adherence
Drug Therapy During Pregnancy
• All drugs cross the placenta to some extent
• Provider must weigh the risk vs. benefit
• Teratogen-induced gross malformations result from exposure
early in pregnancy (Week 3-8)
• Functional impairments result from exposure to teratogens later
in pregnancy
• Drugs that are lipid soluble readily enter breastmilk
Drug Therapy in Pediatric Patients
(Child’s BSA x Adult Dosage)/1.73m² = Pediatric Dose
Drug Therapy in Older Adults
• Altered absorption, distribution, metabolism, and excretion
• Adverse drug reactions more common
• Nonadherence
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