module 11: basic pharmacology
Basic Pharmacology
What is a medication?
a substance used for medical treatment, especially a medicine or drug
Medications helps diagnose, treat, prevent, or manage disease
Differences between Chemical/Generic/Brand Names:
chemical:
Generic and brand: help providers and patients recognize the product more easily
Medication basics
dosage forms: liquids, tablets, capsules, injectables, etc.
Mechanism of action: how a drug produces its effect
Risk vs. benefit: every medication carries potential benefits and possible risks
Four approaches to treatment
Cure: medications that eradicate or eliminate a disease
Manage: medications that control a chronic condition over time
Alleviate: medications that relieve symptoms but may not address root cause
Prevent: medications that reduce the risk of illness or disease
Pharmacology: science of how drugs interact with living systems
2 Concepts:
Pharmacokinetics: what the body does to the drug
ADME
A- Absorption
D- Distribution
M- Metabolism
E- Excretion
Bioavailability: percentage or fraction of a drug that reaches systemic circulation and can have an effect
Volume of Distribution (vD): theoretical space in the body that the drug appears to occupy; helps explain how widely a drug disperses into tissues
Metabolite: substance formed when the body chemically changes a drug, often in the liver; some metabolites are active and can exert therapeutic or toxic effects
Half-Life: the time it takes for the concentration of a drug in the bloodstream to reduce by half; influences dosing intervals and duration of therapy
Pharmacodynamics: what the drug does to the body
Receptor Binding
lock and key
Agonists
exert their effect by activating the receptor
Antagonists
block other substances from activating the receptor
Key Pharmacology Terms
Drug: substance with therapeutic intent
Active ingredient: component producing the drug’s effect
Indication: the condition the drug is meant to treat
Contraindication: circumstances where a drug shouldn’t be used
Dose: the amount to be taken at one time
Frequency: how often the medication is to be administered
Duration: for how long the medication is to be administered
Quantity: how much medication is to be ordered
Adverse Effect: unintended, undesirable or harmful effect of a medication
Side effect: effect of a medication that are not intended as a part of its therapeutic use
Efficacy: drugs ability to produce desired result
Potency: concentration of drug needed for its effect
Prescription vs. Over-the-Counter (OTC)
prescription (RX): requires prescriber authorization, needs pharmacist oversight
Over-the-counter (OTC): readily available for self-medication
Dietary Supplements:
vitamins, minerals, and herbal products
→ may have therapeutic and adverse effects
→ can interact with medications
→ should be included in a patient’s medication history
Medication Use System
Prescribing
Transcribing
Preparing
Dispensing
Administering
Monitoring
Transitioning
Repeat
Pharmacist Job
Inventory management
Quality improvement
Complicance
Research
Medication safety
Operations
pharmacotherapy: treating disease with drugs
lifestyle modifications: changing patient’s diet, exercise, physical surroundings (e.g., removing a pet)
decreasing risk factors: eliminating tobacco, alcohol, illicit drugs, etc.
surgery:
pharmacotherapy: treating w/ prescription or nonprescription medications or dietary supplements
pharmacokinetics:
study of movement of drugs through the body
→ therapeutic doses: doses that produce the desired effects in people
some can be toxic to patients
4 Processes!
absorption
drug enters the blood
EX: through transdermal patch, inhaled into nose or lungs, taken by mouth, injected, etc
bioavailability: describe ratio between amount of drug that reaches the blood & amount of drug placed into body
→ high bioavailability means most of the drug taken ends up getting into systemic circulation via blood
→ low bioavailability means a small amount of drug reach systemic circulation via blood
distribution
movement of the drug through the blood and into various cells or tissues where it exerts its effect
metabolism
chemical changes made to the drug by the body
→ often made by the liver but can sometimes be made by gastrointestinal wall, kidneys, lungs, or blood
liver is main metabolizing organ of the body!
→ has enzymes that metabolize drugs into inactive compounds, or metabolites.
→ they are contained in special structures of the liver, CYP 450 system
CYP 1A2 and CYP3A4 are enzymes that cause drugs to interact w/ each other because they both have effects on or are metabolized by specific enzymes in the system
inactive chemical = prodrug
excretion
the drug or its metabolites leave the body, usually in urine or feces, sometimes through the lungs
→ can either be excreted as active drugs or inactive metabolites
the amount of drug excreted or metabolized to inactive compounds in a given organ or tissue over a certain amount of time is expressed mathematically
→ the time it takes for the serum drug concentration to decline by one-half is called = drugs half-life
Example of 4 Steps:
Alcohol!
alcohol is absorbed in stomach & first part of small intestine
→ moves through blood and into the brain, where it acts as a CNS depressant (slows down transmission of impulses among nerves in the brain)
metabolized in the liver, lungs, urine, and sweat to inactive compounds, including acetaldehyde. amount of acetaldehyde & other metabolites produced is predictably proportional to amount of alcohol in blood & also excreted through lungs and into the breath
pharmacodynamics: relationship between serum or tissue drug levels and drug effects
EX: higher concentration of BP drugs have more antihypertensive effects than do lower concentration
alcohol
→ low 50 mg/dL = euphoria
→ 100 mg/dL = impairment motor functions
→ 150-250 mg/dL = nausea and dysphoria
→ 300 mg/dL = loss of consciousness
→ 400 mg/dL = coma, sometimes death
strength of a drug is amount contained in a unit of the product, whether a tablet or tsp of liquid
EX: diazepam 5-mg tablets or amoxicillin suspension 150mg/5mL
some drugs have doses that can be therapeutic to one, but toxic to another
Dosage Forms Commonly Used
Solid Dosage Forms
pills
→ solid oral dosage forms that are made from a paste; rolled between first finger and thumb, then dried
tablets
→ powders that are compressed w/ enough force that they stay together during shipping but not enough force to prevent from dissolving in the body
→ can be swallowed, chewed and then swallowed, dissolved under the tongue or in buccal pouch, sometimes ground up if patient cannot swallow
capsules
→ gelatin containers w/ loose powders or timed-release beads inside
→ cheapest and easiest solid oral dosage form to make
Liquid Dosage Forms
solutions
→ liquid in which the drug is completely dissolved in the vehicle, making product clear (not necessarily colorless)
→ few oral solutions are used due to bitter taste, rather used for topical preparations (e.g., antibiotic solution used for acne)
suspensions
→ common liquid oral dosage form in which the drug is present in small particles in a flavored vehicle, suspensions never clear and must be shaken well to disperse the drug before a dose is measured
→ ex: liquid antibiotics used orally, anti-infective products used in the ears, etc. can be given to those who will not or cannot swallow
syrups and elixirs
→ used to mask the bitter taste of medicines. syrups are sweetened vehicles, elixirs contain alcohol
→ ex: most cough syrups and elixirs such as phenobarbital
Topical and Other Dosage Forms
creams and ointments
→ semisolid preparations used to deliver drugs to the skin or mucous membranes (nose, vagina). creams are water based and easily washed off, while ointments are fat based and resistant to removal w/ water.
→ ex: hydrocortisone cream and ointment. however they are not always interchangeable (when dealing w/ prescription product, selection must always be what the prescriber intended.
lotions (emulsions)
→ lotions, or products used to soften or deliver drugs to the skin = liquid preparations that have 2 phases. can be water phase dispersed into fat phase, OR small lipid globules dispersed in a water phase.
→ ex: calamine lotion & many others (vaseline intensive care & curel) which rehydrate or soften the skin
transdermal patches and subdermal inserts
→ drugs delivered through the skin using patches that control the rate of drug administration & through use of inserts that are surgically implanted under the skin
→ ex: nitroderm patches & implanon contraceptive inserts; patients ask if patches can be cut, do NOT advise patient either way without consulting pharmacist first, as each patch has specific instructions
Vaginal, Urethral, and Rectal Dosage Forms
suppositories
→ dosage form designed to remain solid at room or refrigerator temperature & to melt and release the drug when inserted into an orifice (opening) of the body
2 most commonly used:
- rectum or vagina, few suppositories are used in urethra of men
→ numerous agents are formulated as rectal suppositories (ex. phenergan, used when patients’ nausea and vomiting are so severe they cannot keep down the oral form of this drug) vaginal suppositories include antifungal agents (monistat)
→ vaginal contraceptives: gels, foams, jellies
Injectable Dosage Forms
injectable solutions
→ most are formulated as sterile solutions. depending on specific drug in solution, it can be injected into arteries, veins, or tissues or can be used to make large-volume solutions that are infused into body through a vein, artery, or peritoneal cavity (space around stomach, intestines, liver, etc)
→ be extremely careful to ensure you use right drug and strength. some drugs cannot be given intravenously, some cannot be injected into muscle
injectable suspensions
→ few injectable products are formulated as suspensions. they are always injected into muscle where they are absorbed into the blood. NEVER should be injected into veins or arteries, since the particles in them can get stuck in lungs & capillaries, causing serious injury or death.
→ ex: antibiotics; absorbed from intramuscular injections quickly. others, including antipsychotic agents, are made to be absorbed in a 3-4 week period
injectable emulsions
→ for when patients are unable to take food by mouth, they must be fed through veins and arteries (parenterally). lipid emulsions provide the fat that people normally get from their diets
→ ex: liposyn, intralipid, nutrilipid
generic name
given by the United States Adopted Names (USAN), a joint project of the American Medical Association, the United States Pharmacopeial Convention, and American Pharmacists Association (APhA).
any company that markets this drug is required by FDA to place its generic name on package label at least half the size of the company’s own brand name
brand name (trade or proprietary) name
given to the company that first marketed or created it.
dosage forms
oral
injectable
intranasal
topical administration
common uses
drugs officially approved for treatment or prevention of certain disease by FDA are called approved indications
adverse (side) effects
drug actions that occur at normal doses of a drug
→ toxic & toxicities refer to those effects that are produced when too much of a drug is used
contraindications/precautions
certain drugs either cannot be used or be used w/ caution in patients w/ more than 1 disease.
→ EX: nonprescription cough and cold products can raise blood pressure and affect blood glucose levels
another contraindication is patient allergy to a drug. when patients allergic to one drug and react similar to other drugs, they are said to exhibit cross sensitivities. these are then listed as precautions
storage considerations
all drugs will degrade or be changed into other substances when exposed to oxygen and/or water
rate at which drugs degrade is a function of their chemical structure and conditions under which they are stored.
→ lower temps slow degradation process
→ some drugs must be frozen, others can be stored at room temp but must be protected by extreme temperatures
drug interactions
when one drug prevents the absorption of another
involves interference w/ or changes in drug metabolism in the liver
food and herbal remedies can also interact w/ drugs