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 medsto 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 Factorsthat 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.
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