Pharmacology – Chapters 1-3

Chemically equivalent
When two formulations of a drug meet the chemical and physical standards established by the regulatory agencies, they are termed chemically equivalent

Biologically equivalent
If two formulations of a drug produce similar concentrations in the blood and tissues, they are termed biologically equivalent

Therapeutically equivalent
If two formulations of a drug have an equal therapeutic effect in a clinical trial, they are termed therapeutically equivalent

Federal regulations and regulatory agencies
Agencies that are involved in regulating the production, marketing, advertising, labeling and prescribing of drugs

Harrison Narcotic Act of 1914
Established regulations for opium, opiates and cocaine (marijuana added in 1937)

Controlled substances act of 1970
Regulates manufacture and distribution of any substance with potential for abuse (DEA)

Omnibus budget reconciliation Act 1990
Pharmacists must provide patient counseling and drug utilization review on all medicaid patients (all patients)

Food, Drug and cosmetic Act of 1938
Prohibits interstate commerce of drugs that have not been shown to be safe and effective

Durham Humphrey law of 1952
Requires that certain types of drugs be sold by “prescription only”

Controlled substance act of 1970
Sets current requirements for writing prescriptions for drugs prescribed in the dental office (DEA)

Who can write prescriptions?
Physicians – Humans
Veterinarians – Animals
Dentists – Dental Problems
Optometrists – Eye problems
And under certain guidelines in certain states so can Physician’s assistants, Nurse Practitioners and Pharmacists

Chemical Name
A drugs chemical name is determined by its chemical structure…sometimes a code name is assigned to the drug and is often used in place of the chemical name because it is easier to write and speak the code name rather than the chemical structure

Generic Name
The “official” name given to a drug before marketing. (NOT CAPITALIZED). Each drug has one generic name.
ie- acetylsalicyclic acid, acetaminophen

Trade Name
AKA: Proprietary Name. If a drug is found to be useful, it is marketed and the company that discovered the drug gives it a trade name. ie – Coke. The trade name IS CAPITALIZED.
Trade names are good for 17 years under the Federal Trademark Law.

Pharmacology
The science of drugs and their properties

Pharmacokinetic
The movement of a drug within the body

Human clinical testing (4 phases)
Phase I – Healthy human volunteers, determine biologic effects, metabolism, safe dose range and toxic effects
Phase II – Larger human groups, ADR’s reported, effectiveness is tested
Phase III – Drug is given to patients that the drug is indicated for, Safety and efficacy must be demonstrated and dosage is determined
Phase IV – Postmarketing survelliance… some drugs can be removed from market due to ADR’s

Schedule I
Highest abuse potential. No excepted medical use. Examples are Heroin, LSD, marijuana

Schedule II
High abuse potential. Needs a written prescription with the providers signature – cannot be called into the pharmacy. NO REFILLS. Examples are oxycodone, morphine, amphetamine, secobarbital

Schedule III
Moderate abuse potential. Prescriptions may be telephoned in, no more than 5 prescriptions in 6 months. Examples are Codeine mixtures (Tylenol #3), hydrocodone mixtures (Vicodin)

Schedule IV
Less abuse potential. Prescriptions may be telephoned. No more than 5 prescriptions in 6 months. Examples are Diazepam (Valium), dextropropoxyphene forms (Davron)

Schedule V
Least abuse potential. Can be bought OTC in some states. An example is some codeine containing cough syrups.

1 teaspoon equivalent
1 tsp = 5 ml

1 tablespoon equivalent
1 Tbs = 15 ml

a or a with a line over it
before

ac
before meals

bid
twice a day

c with a line over it
with

cap
capsule

d
day

disp
dispense

gm
gram

gr
grain

gtt
drop

h
hour

hs
at bedtime

p with a line over it
after

pc
after meals

PO
by mouth

prn
as required, if needed

q
every

qid
4 times a day

s with a line over it
without

sig
write (label)

ss with a line over it
one-half

stat
immediately (now)

tab
tablet

tid
three times a day

ud
as directed

Heading
Name, address and phone #of prescriber
Name, address, age and phone # of patient
Date of prescription

Body
Rx
Name and dose size
Amount to be dispensed
Directions to the patient

Closing
Prescriber’s signature
DEA #
Refill instructions

Drugs
chemical substances used for the diagnosis, prevention or treatment of disease or for the prevention of pregnancy

Potency
The potency of a drug is a function of the amount of drug required to produce an effect

Efficacy
Efficacy is the maximum intensity of effect or response that can be produced by a drug. Related to the maximal effect of a drug, regardless of dose. The efficacy and potency of a drug are unrelated

Median lethal-dose (LD50)
Median lethal-dose (LD50) is the dose when 1/2 of the subjects die. LD50 is only determined on animals

Neurotransmitters (chemical signaling)
transmit messages . There are at least 50 different neurotransmitters.
ie- acetylcholine, norepinephrine, epinephrine, dopamine, serotonin

Local (chemical signaling)
Some organs secrete chemicals near them (not into the circulation).
ie- prostaglandins, histamines

Hormones (chemical signaling)
Hormones are secreted to produce effects throughout the body. Hormones are usually slower than neurotransmitters.
ie – insulin, thyroid hormone, adrenocorticosteroids,

Endogenous
Originating or produced within an organism, tissue or cell

Agonists
An agonist is a drug that has an affinity for a receptor, combines with a receptor and produces an effect. Naturally occurring neurotransmitters are agonists.

Antagonist
An antagonist counteracts the actions of an agonist. There are 3 types of antagonists: 1) Competitive antagonist 2) noncompetitive antagonist 3) physiologic antagonist

Competitive antagonist
a drug that produces NO EFFECT

Noncompetitive antagonist
a drug that binds to a receptor site that is different from the agonist. REDUCES THE RESPONSE OF THE AGONIST

Physiologic antagonist
different receptor site than the agonist. produces an opposite effect via different receptors. PRODUCES OPPOSITE EFFECT OF THE AGONIST

Pharmacokinetics
The study of how a drug enters the body, circulates within the body, is changed by the body and leaves the body. The factors that influence the movement of a drug are divided into 4 steps: Absorption, Distribution, Metabolism, and Excretion

Passive Transfer
Lipid-soluble substances moves across the lipoprotein membrane by a passive transfer process called simple diffusion. It is proportional to the concentration gradient (difference) of the drug across the membrane and the degree of lipid solubility

Active Transport
A process where a substance is transported against a concentration gradient. Transport “carriers” give energy for the transportation of the drug.

Facilitated Diffusion
Does NOT move against a concentration gradient. Pinocytosis (pinching off little caves) may be the process by which substances pass into the cells.

Absorption
The process where drug molecules are transferred from the site of administration to the circulating blood

Weak acids
DO NOT easily penetrate tissues

Weak bases
DO penetrate tissues more easily

Oral absorption of tablet/capsule
goes through 4 stages
1) Disruption
2) Disintegration
3) Dispersion
4)Dissolution

Oral absorption of drug in solution
Drug in solution skips the steps of the absorption of tablet/capsule. Therefore, the ONSET OF ACTION IS QUICKER

Absorption from injection site
Depends on solubility of the drug and the blood flow at the site. Affected by dose form…drugs in suspension are absorbed slower than drugs in solution. The least soluble drugs have a LONGER DURATION OF ACTION

Distribution
Drugs occur in 2 forms in the blood: BOUND TO PLASMA PROTEINS (reservoir for the drug) and FREE DRUG (exerts pharmacological effect). All drugs enter the body and are split between bound and free drugs.

Distribution by Plasma
A drug is absorbed from its site of administration , is distributed to its site of action via blood plasma. The biologic activity of the drug is related to the concentration of free drug. Drugs bind to proteins & act as storage sites.

Half-Life
The amount of time (t1/2) for the concentration of a drug to fall to 1/2 of its blood level.
shorter 1/2 life = leaves body more readily = shorter duration of action
longer 1/2 life = slowly removed = longer duration of action

Blood-brain barrier
For drugs to penetrate the CNS, they need to cross the BBB, therefore they must be highly lipid soluble. *most drugs pass the placenta easily*

Enterohepatic Circulation
Drugs are absorbed via intestines, distributed through the blood, metabolized in the liver and excreted via the kidneys.Once drug is metabolized, the metabolite is secreted via bile into the intestine, broken down by enzymes & released into the body. THE DRUG IS ABSORBED & THE PROCESS CONTINUES

Redistribution
Movement of a drug from the site of action to nonspecific sites of action. Drugs duration of action is affected by redistribution of the drug from one organ to another

Drugs can be metabolized 3 different ways, what are they?
1) Active to Inactive
2) Inactive to Active
3) Active to Active

Active to Inactive
Active parent compound forms an inactive metabolite

Inactive to Active
Inactive parent drug is transformed into an active compound (called a prodrug)

Active to Active
Active parent compound converted to a 2nd active compound then is converted into an inactive product. The action of the drug is PROLONGED

Metabolism
Body changes drug to metabolites so it can be excreted by the kidneys. The metabolite is more polar & less lipid soluble than the parent compound. Metabolites are less likely to be bound to plasma and less likely to be stored in fat tissue.
Metabolism of drugs are divided into 2 types: Phase I & Phase II (first pass effect)

Phase I
Occurs in the liver. Lipid molecules are metabolized 3 ways: Oxidation, Reduction & Hydrolysis

Phase II
Enzymes in liver break down drug through conjugation reactions. Most common conjugation occurs with glucuronic acid (glucuronidation). Basically, drugs bind to compounds already present in the body.

Oxidation
An enzyme system that breaks down (oxidative metabolism) drugs located in the liver. Enzymes are located in the Endoplasmic Reticulum and are called MICROSOMAL ENZYMES

Hydrolysis
Hydrolytic enzymes break up esters & add water. Ester local anesthetics are inactivated by plasma cholinesterases.

Reduction
Reduction reactions are mediated by the enzymes found in the hepatic microsomes.

Enzyme INDUCTION (stimulation)
Microsomal enzymes can be induced (stimulated) by some drugs or by smoking tobacco. Increase in enzyme action causes the drug to be metabolized faster and decreases the blood level of the drug which REDUCES the drugs effect.

Enzyme INHIBITION (slow-down)
With inhibition, the enzymes action is decreased therefore blood levels of the drugs and the effect of the drug will be INCREASED.

When a drug alters the liver microsomal enzymes, what effect can this have on metabolism?
It can either speed up (induction) or slow down (inhibition) metabolism which can either cause a decrease in the drugs effect or toxicity of the drug.

Excretion of drugs
Kidneys (most important route) – URINE, includes glomerular filtration, active tubular secretion & passive tubular secretion.
Drugs are also excreted through the lungs, biliary, milk, sweat, saliva (aspirin, phenytoin, ampicillin, diazepam, pen vk, phenobarbital) & gingival crevicular fluid (tetracycline)

Enteral Route
Placed directly into the GI tract by ORAL or rectal route.

Parenteral Route
Bypasses the GI tract via INJECTION, inhalation & topical

Oral Route (enteral)
Safest, least expensive & convenient route. May cause nausea & vomiting

Injection (parenteral route)
fast absorption, rapid onset, more predictable response. Also the most dangerous & expensive

Parenteral Routes include:
Intravenous, Intramuscular, Intradermal, Intrathecal, Intraperitoneal, Inhalation (nitrous) & topical (benzocaine)

Factors that alter drug effects
Patient compliance
Psychological factors
Tolerance – Tachyphylaxis
Pathologic state
Time of administration
Route of administration
Sex
Genetic variations
drug interactions
Age
weight
environment

Child dose calculations
2.2 lbs = 1 kg
convert lbs to kg by divide the weight in kg by 2
ie- 40kg divided by 2 = 20
then multiply that by the # of mg in the drug (5 mg)
ie- 20 times 5 = 100 mg

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