Transcript Drugs I - Chemistry

Grouping of Drugs
 Names may reflect the conditions for which
they are used (e.g. antidepressants)
 May reflect their chemical characteristics
(benzodiazepines)
 May reflect the effects on body systems
(central nervous system depressants)
Prototype Drugs
 Individual drugs that represent groups of
drugs are called Prototypes
 May be the first drugs of this group to be
developed (e.g., penicillin for antibiotics,
morphine for opioid analgesics)
Drug Names
 Generic Name is related to the chemical
name and is independent of the
manufacturer (e.g., sertraline)
 Trade name is designated and patented by
the manufacturer (e.g., Zoloft)
American Drug Laws and
Amendments
 1938 Food, Drug and Cosmetic Act required
proof of safety, authorized factory
inspections, established penalties for
fraudulent claims
 1952 Durham-Humphrey Amendment
designated drugs that must be prescribed by
a physician and dispensed by a pharmacist
(e.g., controlled substances, etc.)
American Drug Laws cont.
 1970 Comprehensive Drug Abuse
Prevention and Control Act; Title II,
Controlled Substances Act
 Categorized according to potential for abuse
 Regulated distribution of narcotics and other
drugs of abuse
 DEA charged w/enforcing the Controlled
Substances Act
Categories of Controlled Substances
 Schedule I—not approved for medical use
and have high abuse potentials; LSD,
heroin, peyote, ecstasy (3,4 methyenedioxymethamphetamine)
 Schedule II—used medically. High abuse
potential (methadone, meperidine, cocaine,
pentobarbital, Tylox)
Categories of Controlled Substances
continued
 Schedule III-less potential for abuse than I
and II but may lead to psychological or
physical dependence (Vicodin, Tylenol with
codeine)
 Schedule IV-drugs have some potential for
abuse (Valium, Dalmane, Klonopin)
 Schedule V-contain moderate amounts of
controlled substances. An example is
Lomotil (atropine and diphenoxylate)
Pregnancy Categories
 Cat. A-studies in pregnant women failed to
show risk to the fetus
 Cat. B- animal studies have failed to show a
risk to the fetus but there are no adequate
studies in women
 Cat. C-animal studies have shown an
adverse effect on the fetus, no adequate
human studies, benefits may outweigh risks
Pregnancy Categories cont.
 Cat. D-positive evidence of human fetal risk
 Cat. X-animal or human studies have shown
fetal abnormalities or toxicity
Bioavailability
 Is the portion of a dose that reaches the
systemic circulation and is available to act
on body cells
 IV administration is 100% bioavailable
 Subcutaneous administrations has more
rapid absorption than does the oral route
 Mucous membranes allow for rapid and
direct absorption into the bloodstream
Distribution
 Involves the transport of drug molecules
within the body
 After the drug is absorbed into the
bloodstream, it is carried by the blood or
tissue fluids to its sites of pharmacologic
action, metabolism and excretion
 Protein binding is an important factor in drug
distribution
Distribution cont.
 Drug distribution into the CNS is limited because
of the blood-brain barrier
 Blood-brain barrier is composed of capillaries with
tight walls which limits movement of drug
molecules into brain tissue
 Only drugs that are lipid soluble or have a
transport system can cross the blood-brain barrier
and reach therapeutic concentrations in brain
tissue
Distribution cont.
 Drug distribution during pregancy and
lactation is unique as most drugs cross the
placenta or in the case of lactation, pass into
breastmilk
Protein binding
 Most drugs form a compound with plasma
proteins, mainly albumin, which act as carriers
 Only the free or unbound portion of a drug acts on
body cells
 As unbound drug acts on cells, the decrease in
plasma drug level causes some of the bound drug
to be released
 Protein binding allows a part of a drug dose to be
stored and released as needed
Metabolism
 Method by which drugs are inactivated or
biotransformed by the body
 Some drugs yield metabolites that are also
active and exert effects on the body until
they are excreted (normeperidine)
 Most drugs are lipid soluble which aids their
passage across the cell membrane
Metabolism cont.
 Excretion usually is by kidneys. Need to be
water soluble for this to occur. Thus, one
function of metabolism is to convert fat
soluble medications to water soluble ones.
 Hepatic drug metabolism or clearance is a
major mechanism for terminating drug
action and eliminating drug molecules from
the body
Metabolism cont.
 Most drugs are metabolized by the
cytochrome P450 enzymes in the liver
 Liver contains complex system of enzymes,
three of which are key in the metabolism of
medications/drugs
Cytochrome p450
 CYP enzymes catalyze the chemical reactions
which ultimately metabolize the medications
 With chronic administration (greater than 1-3
weeks), some drugs stimulate hepatocytes to
produce larger amounts of drug metabolizing
enzymes (inducers). Enzyme induction
accelerates drug metabolism. Result is that larger
doses of the drug may be need for therapeutic
effects.
Cytochrome p450
 Enzyme inhibition may occur with concurrent
administration of two or more drugs that compete
for the same metabolizing enzymes (e.g., Dilantin,
EES, Tagamet)
 Oral meds are generally absorbed by the GI tract
and carried to the liver. Drug may undergo
extensive metabolism leaving little for systemic
use. This is called the first pass effect.
Excretion
 Refers to the elimination of a drug from the
body
 Most are excreted by the kidneys although
some are excreted in the bile then the feces
Serum Drug Levels
 Lab measurement of the amount of a drug in
the blood at a particular time
 Minimum effective concentration (MEC)must be present before a drug exerts its
pharmacologic action on body cells
 Duration of action-time during which serum
drug levels are at or above the MEC (may
measure serum drug levels when the drugs
have a low therapeutic index)
Pharmacodynamics--Receptors
 Involves drug actions on target cells and the
resulting alterations in cellular biochemical
reactions
 Most drugs chemically bind with receptors at
the cellular level
 Drug-receptor complex initiates
physiochemical reactions that stimulate or
inhibit cellular functions
Pharmacodynamics-receptors
 Receptors vary in type, location, number
and functional capacity
 When drug molecules chemically bind with
cell receptors, pharmacologic effects result
from agonism or antagonism
Pharmacodynamics-receptors
 Agonists-are drugs that produce effects similar to
those produced by naturally occurring hormones,
neurotransmitters and others. Agonists may
accelerate or slow normal cellular processes
depending on the type of receptor activated.
 Antagonists—drugs that inhibit cell function by
occupying receptor sites.
 Not all drugs act on receptors. Examples include:
antacids, osmotic diuretics, chelators.
Variables that affect drug actions
 Dosage
 Route
 Drug-diet interactions. Food may slow
absorption or foods may actually interact
with certain medications (tyramine and MAO
inhibitors; tetracycline and milk products;
ingestion when taking certain
antihypertensive medications)
Variables affecting drug actions
 Drug-drug interations-additive effects such
as seen with sedatives and ethanol.
Synergism as seen with acetaminophen and
codeine.
 Antidote—drug can be given to antagonize
the toxic effects of another drug
Variables that affect drug actions
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Age
Pregnancy
Body weight
Gender-hormonal effects
Pathologic conditions
Placebo response
Variables that affect drug actions
 Genetics-hepatic drug metabolizing
enzymes===acetyltransferase. Rapid acetylators
may need larger than usual dosages and
conversely, smaller doses if slow acetylators
 Glucose-6-phosphate deficiency—develop
hemolytic anemia if take antimalarials or
sulfonamides
 Ethnicity—ACE inhibitors in African Americans
 Tolerance and cross tolerance
Adverse effects of drugs
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CNS
GI
Hematologic-anticonvulsants
Hepatic-acetaminophen, INH
Nephrotoxicity-aminoglycosides, NSAIDS
Hypersensitivity
Drug fever-fever associated w/administration of
some antimicrobials, atropine or TCAs
Adverse Drug Effects
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Drug dependency
Idiosyncrasy
Carcinogenicity
teratogenicity
Toxicology—Drug Overdosage
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General management
CPR
ETT
IV
Check blood sugar, drug screen, liver and kidney
function
5. Charcoal
6. Narcan or possibly antidotes
7. May alkalinize the urine to prevent kidney
damage
Antidotes for Selected Therapeutic
Drugs
 Acetaminophen-mucomyst
 Digoxin-digibind
 Beta blockers-Glucagon (increases
myocardial contractility)
 Phenothiazines-benadryl (EPS)
 Coumadin-vitamin K
 Heparin-protamine sulfate
Antidotes cont.
 Benzodiazepines—flumazenil
 Cholinergics-atropine
 Calcium channel blockers—calcium
gluconate
General Principles of accurate drug
administration
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Six Rights
Right patient
Right drug
Right dose
Right route
Right time
Right documentation
General Principles cont.
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Follow the ‘rights’ consistently
Learn essential information about each drug
Interpret prescriber’s orders correctly
Read labels for right medication and
concentration
Drug Administration
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Minimize the use of abbreviations
Calculate dosages correctly
Measure doses accurately
Use appropriate anatomic landmarks to
identify sites of IM injections-follow
manufacturers recommendations
 Verify client identity
Drug Administration
*****Seek information about the client’s
medical diagnoses and condition in relation
to drug administration
 Be especially vigilant with children to avoid
errors
Legal Responsibilities
 Nurse is legally responsible for safe and accurate
administration of medications
 Nurse is expected to have sufficient drug
knowledge to recognize and question erroneous
orders
 Unit dose wrappings of oral drugs should be left in
place until the nurse is in the presence of the client
and ready to administer the medication
Medication Orders
 Include the full name of the patient
 Generic or trade name of the drug
 The dose, the route and frequency of
administration
 Date, time and signature of the prescriber
Herbal and Dietary supplements
 Feverfew-for migraines, menstrual
complaints. Can cause withdrawal s/s.
 Ginseng-increase stamina, endurance and
mental acuity. Can affect bleeding time, BP,
increase hypoglycemia. No longer than 3
weeks use with Siberian ginseng.
Questions