pharmacology principles

pharmacology

study of drugs

drug

any substance that when taken into a living organism may modify one or more of its functions

pharmacotherapeutics

used intentionally to treat

pharmacokinetics

what the body does to the drug

how the body handles the drug

pharmacodynamics

how the medication works in the body

chemical name

structure

ex: N-acetyl-para-aminophenol

generic name

nonproprietary

ex: acetaminophen

brand name

trade or proprietary

ex: tylenol

classifications of drugs

over the counter

legend

scheduled

over the counter

non prescription

FDA says average person can read label and use it correctly

legend

prescription required from a physician

scheduled

controlled substances

needs to be prescribed

risk of abuse / addiction

food and drug administration

oversees approval and monitoring of drugs

primary concerns are if a drug is effective in treating condition and reasonably safe for human use

controlled substance schedules

1,2,3,4,5

according to their potential for abuse

regulated by the drug enforcement agency

schedule I controlled substance

no medical use

highest potential for abuse

ex: heroin, marijuana, LSD, PCP, GHB

schedule II controlled substance

high potential for physical and psychological dependence

ex: morphine, fentanyl, cocaine, amphetamines

schedule III controlled substance

mild to moderate physical and high psychological dependence

ex: anabolic steroids

schedule IV controlled substance

lower possibility of physical and/or psychological dependence

ex: hypnotics

schedule V controlled substance

least potential for physical / psychological dependance

ex: small amounts of opioids

herbal supplements

medicinal products whose active ingredients are plants or derived from plants

classified as food products

FDA does not regulate

no verification of quality / quantity of ingredients

**cannot patent

**often lacks or has very little clinical data

dietary supplement health and education act

cannot promote treatment of a disease or condition

*** supplements ARE NOT regulated by the FDA prior to marketing

does natural always mean safe

NO

important factors of herbal supplements

patients often do not report use

provider should always ask about use of herbals

may have strong pharmacological activity

possible interactions with other treatment

drug approval process steps

preclinical testing

phase I

phase II

phase III

phase IV and post marketing surveillance

preclinical testing drug approval

determine drug effects and safety

subjects are animals

1-2 years

phase I drug approval

determines effects, safe dose, pharmacokinetics

small number of healthy volunteers

less than 1 year

phase II drug approval

assess drug effectiveness in testing specific disease

limited number patients with target disease

2 years

phase III drug approval

assess safety and effectiveness in larger patient population

large number patients with target disease

3 years

**may have more than one phase III testing

phase IV and postmarketing surveillance drug approval

monitor issues that arise after NDA approval

general patient population

indefinite amount of time

label

FDA approved prescribing info

off label

use of medications for conditions other than what is FDA approved

still have info that it works

generic medication

patent expiration = other manufacturers

generally less expensive

dont have to go through same drug approval process

must show bio equivalence

bioequivalence**

absence of significant differnce in the rate and extent to which the active ingredient becomes available at the site of drug action when administered under similar conditions

threshold dose

point needed to be reached to have any effect from drug

ceiling effect

point on dose response curve where you can increase the dose but the response will not increase

potency

dose that produces a given response in a specific amplitude

*does not have anything to do with efficacy

*more potent drug is not always more efficacious

enteral routes of administration

oral (PO)

sublingual (SL) and buccal

rectal (PR)

oral route of administration

preferred

most convenient

peak drug effects 1-2 hours

absorbed mainly in duodenum

sublingual and buccal routes of administration

alternative to oral route

absorbed through oral mucosa

rectal administration route

alternative to parenteral route in NPO patients

parenteral routes of administration

intravenous (IV)

intramuscular (IM)

subcutaneous (SC, subQ, subcut)

intravenous route of administration

most rapid onset of action

intermittent bolus or continuous infusion

intramuscular route of administration

local or systemic effects

painful

variable / inconsistent to prolonged release

subcutaneous route of administration

local or systemic effects

intermittent injection or continuous infusion

limited by volume that can be injected / infused

intrathecal route of administration

epidural or subarachnoid space

much smaller doses than IV

must use preservative free formulations

intra-articular route of administration

local treatment of joint tendon or bursa

inhalation route of administration

gas, aerosol, dry powder

mainly used for pulmonary pathologies

topical route of administration

local or systemic effects

skin, mucous membrane, eyes, ears

creams / ointments

transdermal route of administration

mainly for systemic effects VIA PATCH

absorption

process by which UNCHANGED drug gets into systemic circulation

to small intestine and blood stream OR through skin into blood stream

bioavailability

EXTENT to which drug reaches systemic circulation

**% of drug that reaches bloodstream

what percentage of bioavailability does intravenous method have

100% because injected directly into bloodstreamd

distribution

reversible process in which drug is distributed into vascular and tissue compartments

what effects distribution

tissue permeability

blood flow

protein bindingw

what effect does protein binding have on medications

proteins are big and can make it harder for medication to enter some tissues

can change if / how drug works

volume of distribution (Vd)

ratio of amount administered to concentration in plasma

*very big = widely distributed

*very small = mainly stays in blood

what protein in blood do drugs normally bind to

albumin

is an unbound drug or a bound to protein drug pharmacologically active

unbound drug

what happens if there is a change in amount of protein in blood

can alter amount of drug available to act

*if increase in amount of unbound drug, may increase therapeutic effect and adverse effects

drug elimination

irreversible loss of drug by metabolism and excretion

**DONE BY LIVER AND KIDNEYS

what organ deals with metabolism

liver

what organ deals with excretion

kidney

metabolism

irreversible process of changing one chemical species into another

mainly occurs in liver

goals: inactivate drug, more hydrophilic to get into urine

metabolite

new species formed from breakdown of medication

can be pharmacologically active or inactive

excretion

irreversible process by which a drug is eliminated from the body

mainly via kidneys (filtration, secretion, reabsorption)

feces

lungs, bile, sweat, saliva, tears, breast milk

elimination rate

rate at which drug is eliminated is determined by amount and frequency of dosage

administration > elimination = accumulation

elimination > administration = ? reach threshold

primary measurements of elimination rate

clearance

half lifec

clearance

volume of blood from which drug is completely removed in a given unit of time

dependent on blood flow to organ, extraction ratio

half life

amount of time required to eliminate 50 % of drug from the body

**drug effectively eliminated in 4-5 halflives

plasma concentration

concentration of drug in blood at a given time

includes bound and unbound drugpe

peak

maximum concentration over dosing interval

trough

lowest concentration prior to next doses

steady state

point where amount of drug is equal to the amount that is eliminated

generally reached in 4 to 5 half lives

what factors can cause variations in response

genetics

disease

drug interactions

age

diet

gender

drug action

alters function of cells / tissues

receptor

drug target that is either on cell surface or in cell cytoplasm

binding affects by drug size and shape

receptor selectivity

non selective: binds all subtypes (more side effects)

selective: binds only one subtype (less side effects)

agonist

binds receptor and produces stimulatory response

antagonist

binds receptor to block the effects

3 ways drugs can activate

agonists vs antagonists

competitive vs noncompetitive

reversible vs irreversible

competitive

can be displaced by another substance

noncompetitive

cannot be displaced by another substance

reversible

drug can bind and unbind from receptor site

irreversible

drug forms permanent bond at receptor site

down regulation

desensitization

limits number of receptors

adverse reaction

side effect

noxious, unintended effect of drug that occurs at normal doses

allergy

abnormal response to a drug characterized by previous exposure and clinical manifestations of a reaction

Q____h

every __ hours

QD, QDay, daily, q24h

every day

BID

two times per day

TID

three times per day

QID

four times per day

PRN

as needed for _______