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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.Â
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