Chapter 1: Pharmacokinetics and Routes of Administration

- Absorption

 Route of admin affects the rate and amount of absorption

o Oral:

 GI pH and emptying time

 Presence of food in the stomach or intestines

 Form of meds (liquid/XR)

o Sublingual/buccal

 Quick absorption systemically through highly vascular mucous membranes

o Inhalation via mouth/nose

 Rapid absorption through alveolar capillary networks

o Intradermal, topical

 Slow, gradual absorption

o SQ/IM

 Highly soluble meds have rapid absorption (10-30min), poorly soluble have slower absorption

 Blood perfusion at site of injection affect absorption

o IV

 Immediate and complete

- Distribution

o Transportation of meds to sites of action by body fluids

o Plasma binding protein: meds compete for protein binding sites within bloodstream, primarily albumin. The ability of med to

bind to protein can affect how much med will leave and travel to target tissues.

- Metabolism

o Primarily occurs in the liver but can take place in the kidney

o Factors that influence metabolism:

 Age (infants/older adults require smaller doses)

 First pass effect: liver inactivates some meds on first pass through and thus require sublingual or IV route (may need

higher dose)

- Excretion:

o Eliminated through the kidneys.

o Kidney dysfunction can result in elevated levels of medications.

- Med Response

o Maintain plasma levels between minimum effective concentration and the toxic concentration:

- Therapeutic index (TI)

o High TI has a wide safety margin.

o Low TI requires monitoring of serum levels.

o Tough levels: obtain immediately before next dose.

- Half-life:

o Time it takes a medication level to drop in the body by 50%.

o Short vs long half-life: long half-life has greater risk for med accumulation in body.

- Agonist: enhance

- Antagonist: blocks

- Routes of admin:

o Oral/Enteral:

 90 degrees upright

 do not mix with large amounts of food

 lean chin in to help facilitate swallowing

o Sublingual/buccal

 Keep med in place until completely dissolved

o Transdermal

 Wash skin with soap and water then dry it thoroughly before placing patch. Place patch on hairless area and rotate sites

to prevent irritation.

o Drops:

 Place drop in center of sac.

 Avoid placing directly on cornea.

 If blink repeat process.

 Apply gentle pressure with finger and a clean facial tissue on the nasolacrimal duct for 30-60 seconds to prevent

systemic absorption.

o Ears:

 Have client lay on unaffected side.