HTHSCI 2H03: Test 1

4 main process

absorption

distribution

metabolism

elimination/excretion

Routes of drug administration

topical, enteral, parenteral

Tropical

applied to site of action

ex. skin, inhalers (inhaled and applied to lungs*), eye and ear drops

*only organ we can reach this way

enteral (gut)

oral

rectal (pediatric patient or pt with nausea/vomiting)

Parenteral

Does not involve GI system

-intravenous(IV): rapid response. Bypasses absorption, very quick. Cannot be used 24/7

-Subcutaneous: for vaccines, pain management. Under skin in fatty area

-Intramuscular: into muscle. for vaccines

Transdermal: Patches. Absorbed into bloodstream. Ex. Birth Control patches

Intrathecal: spinal route, in CSF. Usually used in surgery

Sublingual: Under tongue, higher vascular. Direct effect. Ex. Heart medicine in emergecy

See diagram on slide 3

Drug absorption

the movement of a drug from its site of administration across body membranes, and into the system circulation

Factors affecting drug absorption

Route of administration

drug properties and formulation

drug dosage

blood flow at administration site

digestive motility

drug tract enzymes and pH

intestinal P-glycoproteins (P-Gp)

Factors that impact all routes of drug absorption

Route of administration

drug properties and formulation: liquids have a faster biological effect, some tablets are fast acting; easier to absorb

drug dosage: move across a concentration gradient. Thus, higher dosage= faster absroption

blood flow at administration site. Not highly vascular=less absorption

Factors that impact oral route

digestive motility: had a meal or not

digestive tract enzymes and ph: may destroy drug,

intestinal P-glycoproteins (P-Gp): designed to get rid of toxins through feces, some drugs may bind to these proteins. body cannot reconginze drug as therapeutic. may eliminate some

Drug absorption

orally administered drugs are most commonly available in tablet or capsule form

drugs (the active ingredient) are bound to excipients (inactive ingredients) to facilitate oral administration

these drugs must first dissolve (e.g separate from their excipients) before they can be absorbed.

These excipients can be manufactored to also:

enhance the rate of dissolution: rapid release=excipients let go fast

slow the rate of dissolution: extended release=fewer dosage( excipients hold on) and is dissolved very slow (continuous biological effect)

Alter the actvity of hepatic enzymes, impacting the first effect

Drugs are absorbed via two processes:

passive diffusion and carrier mediated transport

passive diffusion

most common mechanism of drug absorption

movement dictated by the concentration gradient

-drug moves from a higher concentration to a lower concentration til equilibrium is reached

drug must be small in molecular size ans sufficently lipid soluble to pass through biological memebrnaes via diffusion

carrier mediated transport

this process requires energy

drugs can move against the concentration gradient

drugs that are large in molecular size or highly water soluble are actively transported across biological membranes

dissolving, absorption and distrubtion

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absorption and distrbution

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