L33 - overview of absorption via different routes

• within or by intestine

located outside alimentary canal, taken into body or administered in manner other than digestive tract

into epidermis

• fast • precise dosing, large volumes possible • 100% bioavailability

• can be toxic with rapid Cp elevation (can be controlled by infusion) • suitable vein • need professional • cost • duration

• rich capillary bed • passive diffusion of drug • blood flow important • carrier solvent absorption

• large volume • sustained release

• need professional • erratic absorption

passive diffusion into capillaries or lymphatics (peptides)

• slow, sustained delivery • self adminsiteation • implants for long term delivery

• small doses • pain + irritation from repeated injections

alveoli

cornea, skin, mouth

nasal cavity, gi tract

ductal lining

• topical delivery • avoidance of first pass metabolism • drugs sensitive to intestinal metabolism • acid-sensitive drugs • polar compounds with poor oral absorption

small lipophilic drugs, then they enter circulation with up to 100% bioavailability

• air conditioning (temp, humidity, filtration + smell)

• large SA due to microvilli • protective mucus layer • cillia for clearance • mucus acts as physical barrier + chemical barrier

• olfactory epithelium: blood brain barrier not present • drugs can enter brain directly via paracellular diffusion/ axonal transport via olfactory nerves

• for local condiitons • not systemic delivery

• corneal route: major route via transcellular (lipophilic) or paracellular (hydrophilic) diffusion • conjunctival route: drug passes through conjunctiva and sclera, most drugs lost in capillary bed + enter circulation

• local effect • can hold 2-3mL fluid • enzyme activity lower than in gi

• treats respiratory conditions • can reduce dose needed if given by other routes • drugs delivered by nebulisers, dry powder inhalers, metered dose inhalers • lungs oxygenate blood so huge potential for systemic delivery