pharmacokinetics: study of what body does to a drug (ADME)

• absorption: transmission of medications from location of admission to the bloodstream

  • rate: determines how soon medication will take effect

  • amount: determines intensity of its effects

  • route: affects rate & amount of absorption

• distribution: transportation of medications to sites of action (via bodily fluids)

  • influenced by circulation, cell membrane permeability, plasma protein binding (esp. albumin)

• metabolism (biotransformation): changes medications into less active / inactive forms through enzymes

  • influenced by age, increase in enzymes, first-pass effect, similar metabolic pathways, nutritional status

• excretion: elimination of medications from the body

therapeutic index (TI): high = wide safety margin, low = narrow safety margin

• trough level: lowest plasma level

• peak level: highest plasma level

• plateau: medication’s concentration in plasma during a series of doses

half-life: amount of time required for the medication in the body to decrease by 50%

• short half-life: (4-8 hrs)

• long half-life: (~24 hrs) greater risk of toxicity / accumulation

pharmacodynamics: study of what drug does to the body

• agonist: medication that binds to / mimics receptor activity

  • ex: morphine (activates analgesia/sedation/constipation receptors)

• antagonist: medication that blocks receptor activity

  • ex: losartan (blocks angiotensin II receptos on blood vessels which prevents vasoconstriction)

• partial agonist: medication that acts as both agonist and antagonist (limited affinity)

  • ex: malbuphine (antagonist at mu receptors, agonist at kappa receptors → analgesia with minimal resp depression @ low doses)

ROUTES OF MED ADMINISTRATION

oral / enteral

must sit at 90 degree angle

administer with small amounts of food if irritating (ex: analgesics)

avoid administering with interacting foods / beverages

+ safe, inexpensive, easy & convenient

- highly variable absorption, inactivation may occur in GI tract / by first-pass, pt must be conscious & cooperative

• contraindications: vomiting, decreased GI motility, no gag reflex, difficulty swallowing, decreased LOC

sublingual / buccal

directly enters bloodstream and bypass liver

ng / g- tubes

use liquid forms if available or crush

do not administer sublingual through NG tube

administer each medication separately

dissolve contents in 15-30 mL sterile water, flushing before & after each med, and after all meds with 15-30 mL warm sterile water

topical

+ painless, limited adverse / systemic effects

do not apply with bare hands

wash area with soap & water prior to application

transdermal

wash area with soap & water prior to application

rotate application site daily

eyes

apply gentle pressure with tissue on tear duct for 30-60 secs after administration to prevent systemic absorption

wait 5 mins between each medication per eye

ears

have pt remain on side for 2-3 mins (as tolerated) after instilling ear drops

nose

instruct pt to not blow nose for 5 mins after drops or spray

rectal suppositories

position pt in left lateral / lateral semi-prone recumbent position

insert just beyond internal sphincter

have pt remain flat / left lateral position for at least 5 mins after

vaginal

position in modified lithotomy / dorsal recumbent position

insert along posterior vaginal wall: 3-4” (suppositories) 2-3” (creams, jellies, foams)

remain supine for at least 5 mins after

metered dose inhalers (MDI)

shake 5-6 times before use

take a deep breath, exhale, press inhaler, take slow inhalation (3-5 secs), hold breath (10 secs), remove inhaler, slowly exhale

dry-powder inhalers (DPI)

do NOT shake

exhale completely, take deep breath, hold breath (5-10 secs), remove inhaler, slowly exhale

parenteral (anything besides oral)

use vastus lateralis (infants-toddlers)

use ventrogluteal site for IMs and injecting volumes more than 2 mL

use deltoid for 1 mL volume or less

intradermal

insert needle with bevel up (small bleb will appear)

do NOT massage site after injection

subcutaneous

select site with adequate fat-pad size

pinch skin & inject at 45-90 degree angle (90 for obese pts)

intramuscular

inject at 90 degree angle

+ use for poorly soluble meds and for administering meds with slow absorption for extended period of time

- more costly, inconvenient, pain (local tissue & nerve damage), infection risk at injection site

intravenous

16 g (trauma) 18 g (surgery / blood administration) 22-24 g (children, older adults, pts with medical issues)

hand/arm peripheral veins preferred

+ rapid onset & immediate absorption, control over precise amount administered, large fluid volumes

- more costly, inconvenient, immediate absorption = dangerous if wrong dosage/med, increased infection/embolism risk, distribution inhibited by poor circulation

epidural

placed by clinician

used for IV opioid analgesia

VITAMINS: water-soluble

• B1 (thiamine):

  • beriberi or Wernicke Korsakoff syndrome (deficiency)

• B2 (riboflavin):

  • deficiency: red tongue, cracked lips/corner of mouth

• B3 (niacin):

  • pellagra (deficiency)

• B6 (pyroxidine): involved in metabolism, amino acid absorption, and neurotransmitter synthesis

  • deficiency: abnormal CNS function

• B12 (cyanocobalamin): involved in DNA synthesis & cell division; needs intrinsic factor to be absorbed through oral administration

  • pernicious anemia (deficiency)

• C (ascorbic acid): active in oxidation-reduction rxns, used in metabolic activities, enhances iron absorption

  • scurvy (deficiency)

VITAMINS: fat-soluble

• A

• D

• E

• K

MINERALS: inorganic elements/salts that bind with enzymes, etc.

• calcium: high concentration in bones & teeth; sufficient vit D required for absorption: essential for nervous, muscular & skeletal systems

  • hypocalcemia (deficiency)

    • rickets (children)

    • osteomalacia, osteoporosis (adults)

  • hypercalcemia (toxicity): N/V/D

  • chelation- calcium salts binding with tetracyclines to → insoluble complex (ex: !digoxin!)

• magnesium: essential for metabolism, nerve physiology, & muscle contraction; used for (pre)/eclampsia

  • hypomagnesia (deficiency)

  • hypermagnesia (toxicity): tendon reflex loss, CNS depression, heart block, resp distress, hypothermia, difficult BMs

• phosphorus: “building block”

• zinc: essential in metabolic reactions of proteins & carbohydrates, normal tissue growth & repair

• folic acid: used in pregnancy to prevent CNS issues in fetus

  • women of childbearing years should be taking 400 mcg/day

• iron

• potassium: !never push K bolus! do not use with K+ sparing diuretics or ACE inhibitors, or pts with chronic kidney disease

  • hypokalemia (deficiency): <3.5

  • hyperkalemia (toxicity): >5