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Lecture 5:
Principles of Drug Administration
Drug Therapy in Special Populations
Objectives
Upon completion of this lecture, student will be able to
1. Describe the roles and responsibilities of nurses regarding
safe drug administration
2. Discuss the different routes of drug administration
3. Discuss the influences of the patient’s age on the effects of
drugs and drug responses
4. Discuss the pharmacological process and associated
changes in various patient age groups.
24-Nov-18
o Nurses are continually challenged to ensure that their
patients are given the correct medication at the correct time.
o Although many obstacles are encountered by nurses on
daily basis, nurses are both ethically and legally responsible
for correct administration of drugs.
o For safe and accurate drug administration (correct drugs
administration), the nurses
must have a physician’s order before administration of
medication
should use the “Six Rights” and three checks as a guideline
should minimize the use of abbreviations for drug names,
doses, routes of administration, and times of administration
because errors occurring with incorrect or misinterpreted
abbreviations. 24-Nov-18
Common abbreviations and their meanings
24-Nov-18
• Pharmaceutical Formulation: الصيدالنيةصياغة المستحضرات
• It is the method by which a drug is prepared – the process in which different chemical substances, including the active drug, are combined to produce a final medicine product.
• Dosage Form It is the form in which the above : شكل الجرعةformulation can be administered to a patient. e.g. as tablet, capsule, syrup or injection etc.
o Drug Formulation and dosage forms vary according to the:
• Drug’s chemical and physical characteristics, • Reason for use, and • Route of drug administration. • Some drugs are available in only one dosage form; others
are available in multiple dosage forms — choosing a form that is best received by the patient will lead to a better total outcome.
24-Nov-18
Most of drugs can be administered by a variety
of routes – Major routes of drug administration
include:
• Enteral,
• Parenteral, and
• Topical
24-Nov-18
Additional methods of administration
• Intra-lesional (into a lesion)
• Intra-thecal (instilling drugs directly into CSF) or intra-spinal
• Intra-cardiac (into the heart)
• Intra-pleural
• Intra-arterial (administration is not by direct arterial injection but by means of a catheter that has been placed in an artery)
• Intra-articular (into a joint)
• These methods are used by physicians & in some cases by advanced practice registered nurses for medication administration.
24-Nov-18
Factors that determine the choice of drug administration routes, include:
1) Physical and chemical properties of the drug (drug characteristics).
2) The dosage form in which the drug is available
3) Site of desired action, systemic or local effects
4) Rate and extent of absorption of the drug from different routes
5) Effect of digestive juices and first pass metabolism on the drug.
6) Rabidity with which the response is desired – onset of action (routine treatment or emergency).
7) Accuracy of dosage required (I.V. & inhalation can provide fine-tuning).
8) The patient’s age and condition – unconscious, vomiting, etc. (Patient related factors or patient characteristics)
24-Nov-18
Advantages Disadvantages
• Easy and Convenient
• Non-invasive, and often
painless
• Potentially reversible, and
hence safer than parenteral
routes – no risk of fluid
overload, infection, or
embolism
• Ideal for self-medication -
does not need assistance
• Inexpensive
• Variability: absorption can be highly
variable from one patient to another
→ difficult to control the conc. of a
drug at its sites of action, and
therefore makes it difficult to control
the onset, intensity, and duration of
responses.
• Inactivation of some drugs by
gastric acid and digestive enzymes
• Possible nausea and vomiting from
local irritation
• Patient must be conscious and
cooperative 24-Nov-18
.
• The enteral route – Oral drug administration (PO) includes drugs
given by mouth and swallowed – designed to pass through the
gastrointestinal tract. It is the oldest and most common route
Sublingual or buccal route
24-Nov-18
• For sublingual and buccal administration, the tablet or
pellet containing the drug is not swallowed but kept in
the mouth –sublingually(under the tongue) and
buccally (held between the gum and the cheek).
• Parenteral: introduction of drugs by any route other than the
oral-gastrointestinal route (enteral) or topical, usually refers
to administration of drugs by injection.
• This route takes the drug directly into the tissue fluid or
blood without having to cross the intestinal mucosa.
• The four routes that nurses commonly use to administer parenteral medications are:
Intramuscular (I.M)
Intravenous (I.V)
Intra-dermal (I.D)
Subcutaneous (S.C or SQ) 24-Nov-18
• Advantages of parenteral routes: • This route provide a rapid onset of action & ensure high blood
levels of the blood. (Drug action is faster – emergencies).
• Used for drugs with poor absorption from intestine (e.g. heparin) or unstable in the GI environment (e.g., insulin).
• Can be used for unstable of seriously ill patients, unconscious, uncooperative, vomiting patient.
• Not cause gastric irritation and vomiting.
• No chances of interference by food or digestive juices.
• Liver is bypassed
• Disadvantages of parenteral routes: • The preparation has to be sterilized.
• The technique is invasive and painful.
• It needs assistance of another person (though self-injection is possible – insulin).
• There is chance of local tissue injury. In general, parenteral route is more risky than oral (enteral) route
24-Nov-18
Topical drugs are those applied locally to the skin or the membranous
linings of the eye, ear, nose, respiratory tract, urinary tract, vagina, and
rectum. It is often more convenient as well as encouraging to the patient.
In the form of lotion, ointment, cream, powder, paints, drops, spray,
suppositories or pessaries, (including transdermal patches).
These applications include the following:
• Dermatologic preparations. Drugs applied to the skin, the topical
route most commonly used.
• Instillations and irrigations. Drugs applied into body cavities or
orifices. These routes may include the eyes, ears, nose, urinary
bladder, rectum, and vagina.
• Inhalations. Drugs applied to the respiratory tract by inhalers,
nebulizers, or positive-pressure breathing apparatuses.
24-Nov-18
Transdermal Delivery System (Transdermal
therapeutic system). • The use of transdermal patches (skin patch on which the
drug has been implanted) provides an effective means of
delivering certain medications.
• Drugs administered by this route are readily absorbed
from the skin and provide systemic effects. Drugs to be
administered by this route avoid the first-pass effect in the
liver and bypass digestive enzymes
• e.g., nitroglycerin for angina pectoris and scopolamine for
motion sickness, estrogen, fentanyl,…..
24-Nov-18
• This type of drug system are slowly absorbed from the skin
patches and maintains a relatively constant blood
concentration. Thus administration is less frequent than
when the drugs are given by another route.
• In addition, this drug system causes fewer adverse
reactions and reduces the possibility of toxicity
24-Nov-18
Inhalation Routes
This route is particularly effective and convenient for
patients with respiratory complaints (such as asthma or
chronic obstructive pulmonary disease), because the drug is
delivered directly to the site of action, thereby minimizing
systemic side effects. E.g., bronchodilators, such as
albuterol, and corticosteroids, such as fluticasone.
This route also can be used for systemic effect, e.g. general
anesthesia.
24-Nov-18
Drug Therapy in Special Populations
Drug therapy across the life span
Life Span Considerations of Medication
Administration, include:
1) Drug therapy during pregnancy and breast-feeding
2) Drug therapy for pediatric patients
3) Drug therapy for Geriatric patients
24-Nov-18 Dr. Utoor Talib
Drug Therapy during Pregnancy and Lactation • The clinical challenge is to provide effective treatment for
the mother while avoiding harm to the fetus or nursing
infant.
• Drug use during pregnancy is common – between one/half
and two/thirds of pregnant women take at least one medication, and the majority takes more.
• In pregnant patients, as in all other patients, the benefits of
treatment must balance the risks – risks apply to the fetus as
well as the mother.
• Unfortunately, the risks for most drugs used in pregnancy
have not been established. The clinician is obliged to
balance risks versus benefits, without knowing what the
risks really are.
• Drugs are most commonly used during pregnancy as
nutritional supplements (iron, vitamins, minerals) 24-Nov-18
Dr. Utoor Talib
• Physiologic Changes During Pregnancy
• Physiologic changes in the kidney, liver, and GI tract that can
alter drug pharmacokinetics. Because of these changes, a
compensatory change in dosage may be needed.
• For some drugs, distribution and hepatic metabolism and
excretion increases during pregnancy – change in cardiac output,
plasma volume, and regional blood flow
• Tone and motility of the bowel decrease in pregnancy, causing
intestinal transit time to increase. Because of prolonged transit,
there is more time for drugs to be absorbed.
• Placental drug transfer: Essentially all drugs can cross the
placenta, although some cross more readily than other –drugs
that are lipid soluble cross the placenta easily, whereas drugs that
are ionized, highly polar, or protein bound cross with difficulty.
• Gestational Age and Drug Therapy
• Factors affecting Teratogenesis: Sensitivity of fetus to drug is
dependent upon
Timing of exposure
Ability of drug to pass into the fetal circulation
Intensity of exposure – Dosing, frequency and duration
• When drug is given in relation to the developmental stage –timing of exposure:
Pre-implantation (conception week 2)
Embryonic period (week 3 week 8 post conception)
Fetal period (week 9 40 weeks post conception or until birth term)
**Exposure during pre-implantation, the teratogen acts in an all-or-none response, because exposure to a teratogen either causes death of the embryo or has no effect – if dose is high enough →the fetus will die, if dose is sub-lethal → the fetus will recover
• Drugs are less likely to cause congenital malformations during this period because the baby’s organ systems have not yet begun to form.
** During the embryonic period, there is rapid development of
internal structures. This is the period of maximum sensitivity
to teratogens.
• Teratogenic agents taken during this phase can lead to
structural malformation and spontaneous abortion. The
specific abnormality depends on which organ is forming at
the time of exposure.
• Exposure to teratogens during the 1st trimester results in
gross malformations
** During the fetal period, there is continued growth and
maturation of the baby’s organ systems.
Exposure to teratogens during the fetal period (2nd and 3rd
trimesters) is more likely to produce slowed growth or
impaired organ function, rather than gross structural
malformations.
24-Nov-18 Dr. Utoor Talib
• Pregnancy Drug Categories
In 1983, an effort to prevent teratogenicity effects, the Food and Drug Administration (FDA) established a system for classifying drugs according to potential harm to the fetus.
According to this system, drugs can be put into one of five categories: A, B, C, D, & X.
Drugs in Risk Category A are the least dangerous. In contrast, drugs in category X are the most dangerous; these drugs are known to cause human fetal harm.
Drugs in category B, C & D are progressively more dangerous than drugs in category A & less dangerous than drugs in category X.
24-Nov-18 Dr. Utoor Talib
24-Nov-18 Dr. Utoor Talib
Drug therapy during Lactation
Drugs taken by lactating women can be excreted in breast
milk. As a general rule drugs given to nursing mothers
reach infants in much smaller amounts than drugs given to
pregnant women. Most drugs can be detected in milk, but
concentrations are generally too low to be harmful.
Drugs that are lipid soluble enter breast milk readily,
whereas drugs that are ionized, highly polar, or protein
bound tend to be excluded.
Nonetheless, prudence is always in order. If possible, drugs
should be avoided during breast-feeding; however, patients
with chronic illnesses may require medication therapy for
their own health.
24-Nov-18 Dr. Utoor Talib
Drug Therapy in Pediatrics • Most drug use in pediatrics is empiric in nature because few studies
have been done in that population. Until recently, the FDA did not
require drug trials in children. As a result, for many drugs given to
young patients we lack good information on dosing, pharmacokinetics, and the therapeutic and adverse effects.
• Drug therapy in pediatric patient requires special consideration because of the child’s changing size, developmental level, and organ function.
• Pediatric patients respond differently to drugs than do adults
(middle-aged people). These differences allow pediatric patients to
be a greater risk for medication errors, and for prolonged and intense responses.
•
• Pediatrics = all patients under age 16 • Pre-mature infants (< 36 weeks gestation), Full-term infants (36 – 40
weeks gestational age), Neonates (birth –1 month), Infants (1 month – 1 year), and Children (1–12 years old), and Adolescents (12 –16 years old)
24-Nov-18 Dr. Utoor Talib
Pharmacokinetic factors specific to pediatrics include:
Decreased gastric acid production and slower gastric emptying time.
Drugs are usually given less often because they are metabolized
(involves first-pass metabolism) and excreted slowly, due to immature
liver and kidney function. Complete maturation of the liver and
kidney develops by 1 year.
Increased absorption of topical medications (greater body surface area
and thinner skin). This ↑the risk of toxicity from topical drugs.
Decreased serum protein-binding sites (until age 1). There may be an
increase in serum medication level of protein-binding medications.
Intramuscular administration: drug absorption following IM injection
in the neonate is erratic and slower than in adults. Delayed absorption
is due in part to low blood flow through muscle during the 1st days of
postnatal life.
24-Nov-18 Dr. Utoor Talib
Site selection for intramuscular injections depends on age and size. In
infants, use thigh muscles. In children older than 18 months of age,
use deltoid muscles; injections are considered less painful than in
thigh muscles. In children older than 3 years of age, use gluteal
muscles.
Blood-brain barrier: the BBB is not fully developed at birth making
infant much more susceptible to drugs. As a result, drugs and other
chemicals have relatively easy access to the CNS, making the infant
especially sensitive to drugs that affect CNS function. Accordingly, all
medicines employed for their CNS effects (e.g. morphine,
Phenobarbital) should be given in reduced dosage.
By the age of 1 year, most pharmacokinetic responses are similar to those in adults.
• Hence, drug sensitivity in children over the age of 1 is more like that
of adults than of the very young – except drug-metabolizing
capacity is markedly elevated until the age of 2 years, and then
gradually declines. A further sharp reduction takes place at puberty, when adult values are reached).
24-Nov-18
Dr. Utoor Talib
Drug Therapy in Geriatric patients (65+ years) • Drug therapy in the elderly represents a special therapeutic
challenge:
− older pts are more sensitive to drugs than younger adults
− exhibit more variability in response
− they experience more adverse drug reactions & drug-drug interactions.
Social, economic, physiologic, and age related health factors place elderly patients at high risk for medical problems.
The goal of drug therapy in the elderly may be “care” rather than “cure”, elderly suffer from chronic illnesses, the usual objective is to reduce or control symptoms & improve quality of life since cure is generally impossible.
To help ensure that drug therapy is safe and effective (as possible), individualization of treatment is essential – to achieve the desired intensity and duration of effect of the drug in each individual patient.
24-Nov-18 Dr. Utoor Talib
The age-related physiologic changes or aging process can affect all phases of pharmacokinetics, there is a gradual, progressive decline in organ function; this decline can alter the absorption, distribution, metabolism, and excretion of drugs.
o Increased gastric pH (alkaline)
o Decreased GI motility and gastric emptying time
o Decreased blood flow through cardiovascular system, liver, and kidneys
o Decreased hepatic enzyme function
o Decreased kidney function and glomerular filtration rate
o Decreased protein-binding sites
o Decreased body water, increased body fat, and decreased lean body mass
Pharmacokinetic changes may be minimal in patients who have remained physically fit, whereas they may be dramatic in patients who have aged less gracefully.
24-Nov-18 Dr. Utoor Talib
Nursing interventions for older adults: Decreasing the risk of adverse medication effects
Promoting compliance.
• Measures that can reduce the incidence of adverse drug reactions include: The majority of adverse drug reactions in the elderly are avoidable and dose related – not idiosyncratic.
o Taking detailed drug history, including over-the counter medications.
o Accounting for the pharmacokinetic and pharmacodynamic changes that occur with aging.
o Initiating therapy with low doses.
o Assess/monitor for therapeutic and adverse effects
o Monitoring clinical responses and plasma drug levels to provide a rational basis for dosage adjustment.
o Employing the simplest regimen possible.
o Monitoring for drug-drug and drug-food interactions & iatrogenic illness.
o Periodically reviewing the need for continued drug therapy, and discontinuing medications as appropriate.
o Encouraging the pt to dispose of old medications. 24-Nov-18
Dr. Utoor Talib
Dr. Utoor Talib 24-Nov-18