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.