Inhalation
Sublingual, buccal
Intradermal, topical
Oral
Subcutaneous, intramuscular
intravenous
inspiratory effort
Meds must pass through the layer of cells that line the GI tract.
NO barriers
Swallowing before dissolution allows gastric pH to inactivate the medication.
capillary walls have large spaces between cells, no significant barrier.
close proximity of epidermal cells