Basics Flashcards
Absorption
Getting drug to blood
Distribution
- Movement of drug to body’s tissue
- Results in therapeutic and adverse effects
Metabolism
Breaking drug down
Excretion
Getting drug out of body
Factors Influencing Drug Absorption
- Route
- Drug properties
> molecular size, lipid solubility, pH - Pt properties
> surface area of absorptive site, blood flow to site of absorption
Oral Route
- Most meds absorped in small intestine
- Due to first-pass metabolism, the oneset of action for most oral drugs is 30-60mins
Sublingual
Absorbed into highly vascular tissue under tongue; rapid actions
Topical
- Delivers drug directly to affected area
- Minimal systemic absorption
Transdermal
- Provides constant rate of drug absorption
- Always apply to intact skin
> broken skin incrs absorption
Intravenous (IV)
- Full strength: immediate onset & fully absorbed; more likely to cause toxic effects
- If admining more than 1 drug at same site, must be compatible
Intramuscular (IM)
- Absorbed directly into capillaries in muscle & sent into circulation
- Men more vascular muscles than women; men reach a peak lvl faster than women
Subcutaneous (SQ)
- Slowly absorbed; timing of absorption varies depending on fat content & state of local circulation
- Incrd adipose tissue = dcrd absorption (less capillaries)
Bioavailability
- IV: 100% absorption, 100% biooavailable
- IM/SQ: 100% absorption, <100% bioavailable
- Oral: <100% absorption, 0-70% bioavailable
Factors Affecting Distribution
-
Blood flow to organs/tissues
> areas of rapid perfusion/distribution: heart, liver, kidney, brain
> areas of slow distribution: muscle, skin, fat - Ability to cross blood-brain barrier or fetal/placental barrier
-
Drug properties
> Protein binding (albumin); highly protein bound = less available for distribution
> highly water soluble drugs stay in bloodstream; go more places
> highly lipid-soluble drugs more readily lipid cell membranes & deposit in adipose tissue
Primary Site for Metabolism
- LIVER
- hepatic microsomal enzyme system (P-450 system)
- inactivates/breakdown drug for excretion; some to active form (prodrug)
- changes in hepatic microsomal enzyme can affect drug metabolism
Factors Affecting Metabolism
- Metabolic activity may be dcrd in some pts
> infants & elderly
> genetic disorders
> severe liver disease - Dosages reduced in dcrd liver func to prevent toxicity
Nursing Considerations for Metabolism
- Liver disease is a caution/contra when admining certain drugs
- Monitor liver functions to avoid drug toxicity or injury to liver
Primary Site for Excretion
- KIDNEY
- Liver/Bowel are secondary
> drug processed by liver, released into bile, eliminated in feces
Factors Affecting Excretion
- Kidney dysfunction
> drugs not excreted effectively; reach toxic lvls - Nurse: monitor kidney func to avoid drug toxicity or AKI
Older Adult: Physiological Changes of Aging r/t Pharm
cardio
gastro
hepatic
renal
- Cardiovascular: dcrd CO
-
Gastrointestinal:
> incrd gastric pH & dcrd peristalsis
> dcrd absorption - Hepatic: dcrd enzyme production & dcrd blood flow to liver
- Renal: dcrd blood flow, GFR, & overall function
Older Adult: Pharmacokinetic Alterations - Absorption
Changes can result in dcrd absorption of oral drugs
Older Adult: Pharmacokinetic Alterations - Distribution
- Dcrd total body water incrs concentration of med; risk for toxicity
- Dcrd protein (albumin); greater amnt of free drug; risk for toxicity
Older Adult: Pharmacokinetic Alterations - Metabolism
Enzyme activity dcrd due to dcrd function; incrd risk for toxicity
Older Adult: Pharmacokinetic Alterations - Excretion
Dcrd # of nephrons & GFR; incrd risk for toxicity
Anaphylaxis
- Involves massive systematic response (histamine)
- Leads to bronchoconstriction, shock, & death
- CMs:
> hypotension
> tachycardia
> dyspnea
> edema
> hives
> itching
> resp or cardiac arrest
Allergic Reactions: Nursing Interventions
- Stop administration immediately
- Apply oxygen (if needed)
- Call rapid response team if severe
- Notify PCP
- Admin IV fluids as ordered
- Admin antihistamines as ordered
Pharmacokinetics
What the body does to the drug
Agonist (Receptor Theory Type)
- Drugs interact directly w/ receptor sites
- Cause same activity of natural chemicals would case at tht site
- EX: insulin; beta-agonist
Cholinergic Agonist
- Parasympathetic branch
- Mimics acetylcholine
- Incrs saliva production
- Slows HR
- Constricts bronchioles
- Stims digestive process
- Incrs urination
- Common use: Alzheimer’s disease
Cholinergic Mnemonic - SLUDGE
S = salivation
L = lacrimation
U = urination
D = diaphoresis (sweating)
G = GI upset
E = emesis (vomiting)
Adrenergic Agonist
- Sympathetic branch
- Tachycardia & vasoconstriction
- Bronchodilation
- Dcrd GI motility
- Glycogenolysis (incrd bld glucose)
- Constricts bladder sphincter
- Uses: cardiac & respiratory
- Sympathomimetic
(think of switching the fight or flight ON)
