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Life Span Consideration
Chapter 7
Drug Absorption
• Absorption:
– Process by which a drug is transferred from its site
of body entry to circulating body fluids (blood,
lymph) for distribution
Drugs applied to the Skin
• Absorption of drugs applied to the skin (topical) is usually
effective in infants
– Outer layer of skin not fully developed
– Skin is more fully hydrated
– Enhanced with plastic-coated diapers
• Plastic increase hydration of the skin
– Inflammation of skin also increases the amount of drug
absorbed
• Ex. Diaper Rash
• Skin absorption in older patient is often hard to predict
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Drier skin
Wrinkled skin
Decreased number of hair follicles
Decreased cardiac output
• Decreases the amount of blood flow to tissues
Drugs Given Orally
• Most drugs are administered orally
– Some tablets and capsules are too large for
children and older patients
• With permission some tablets can be crushed & mixed
with food
– Some tablets cannot be crushed:
» Timed-release
» Enteric-coated
» Sublingual
• Liquids can also be ordered
Oral Medications
• Factors to consider:
– Teeth:
• Do not give chewable tablets to anyone lacking teeth or
loose teeth
– Saliva flow:
• Lessens with age
Gastrointestinal Absorption
• GI absorption of drugs is influenced by disease
processes other factors including:
– Gastric pH:
– Gastric emptying
– Motility of the GI tract
– Blood flow
Drug Distribution
• Distribution:
– Mode in which drugs are transported by
circulating body fluids to the sites of action
(receptors) and to the sites of metabolism and
excretion.
• Most drugs are transported:
– Dissolved in the circulating body water (blood)
– Bound to plasma proteins with the blood
Drug Metabolism
• Metabolism:
– Process by which the body inactivates drugs
• Enzymes are factors in drug metabolism
– Enzymes:
» Substances produced by body cells
» Enzymes break down glucose and other nutrients to release
energy for cellular work.
– Enzyme systems in the liver provide the major
pathway for drug metabolism
• Liver weight, number of functioning liver cells and liver
blood flow decrease with age, therefore metabolism is
slower in elderly
• Other factors that may affect metabolism include:
– Genetics, smoking, diet, gender, liver disease, other medications
Drug Excretion
• Excretion:
– Elimination of a drug from the body
• Metabolites of drugs, and sometimes the drug itself,
are eventually excreted from the body
– Excreted mainly through urine and feces
– Minor routes of excretion include:
» Skin
» Lungs
» Saliva
» Breast Milk
Therapeutic Drug Monitoring
• Measurement of a drug’s concentration in
body fluids
– Completed in order to determine the drug dosage
and the blood level of the drug in relation
Assisting with the Nursing Process
• Vital signs & urinary output are used to plan
dosages and monitor the effects of drug therapy
– Children:
• Great risk of complications as bodies & organs are
developing
– Elderly:
• Great risk for drug interactions and/or drug toxicity
– Assist through the use of drug organizers, destroying old
prescriptions, and breaking/crushing large tablets if allowable
– Pregnancy / Breast Feeding:
• Risk of injuring developing fetus