Basic Principles III Flashcards
passive processes
simple diffusion, facilitated diffusion, filtration
active processes
active transport, micropinocytosis
weak electrolyte drugs
ionized forms do not diffuse, non-ionized forms diffuse and are lipid soluble. Follow the concentration gradient
weak acid drugs
will be in HA form in the stomach fluid (low pH), but when they diffuse to plasma (higher pH), will mainly be in H + A form
weak base drugs
will be in H + B form in stomach fluid (low pH), but when they diffuse to plasma, they will mainly be in the HB form
enteral administration
uses a portion of the GI tract
parenteral administration
does not use the GI tract
considerations for routes of administeration
planned use of medication, clinical setting (acute vs chronic), rapidity of onset of desired action, specific target organ that drug is intended to reach
oral advantages
easy, safe, self administered, cheap, prolonged absorption causes prolonged effect
oral disadvantages
may be too slow, unpredictable, and variable. May be too irritating or destroyed by gastric acids. May be completely metabolized on first pass through liver. Not available for comatose or vomiting patients
rectal advantages
useful for infants, coma, vomiting. Useful for bad tasting drugs. Useful for drugs destroyed in upper GI tract. Avoids liver. For local action in rectum
rectal disad
poor compliance. Absorption may be erratic. Possibility of rectal irritation
sublingual advantages
bypasses liver when first absorbed. Rapid absorption
sublingial diasadvan
must be soluble in saliva, not distasteful, have appropriate pKa for rapid absorption. Must be small tablets.
IV advantages
rapid effect, can watch response and titrate dose, all dose enters blood, good for when you cant do oral, good for irritating drugs or large volumes of drugs. Allows hypertonic solution to be administered
IV disadvan
cost, skill in administration, danger of infection, embolus formation, anaphylactic rxn, adverse cardiovascular effects if given too fast, painful
intraarterial advantages
administration of radio-opaque material for visualization of circulatory tree. High concentration of drug going to local area when desirable.
intraatertial disadvan
cost, skill in administration, danger of infection, embolus formation, anaphylactic rxn, adverse cardiovascular effects if given too fast, painful
intramuscular advantages
when oral isnt avail, may be less variable absorption, may be less painful than subcutaneous, more rapid absorption than subcutaneous, possiblity of slowing absorption to prolong effect
intramuscular disadvan
pain, sterile, posible local necrosis, lag period before onset, accidental injection in vein possible, not to be used after anticoag
subcutaneous advantages
absorption usually slower than intramuscular, more prolonged effect
subcutaneous disadvan
pain, sterile, posible local necrosis, lag period before onset, accidental injection in vein possible, not to be used after anticoag
intrathecal advantages
when local effect on CNS required and other routes are unsatisfactory
intrathecal disadvan
skill needed, danger of spinal cord injury
topical advantages
for local action on or under skin/membrane. Non invasive
topical disadvan
difficulty of absorption through skin. Danger of excessive absorption through membranes and systemic toxicity
inhalation advantages
rapid absorption for systemic effect. High concentration attainable for local effect. Self administration possible
inhalation disadvan
possible excessive absorption and systemic toxicity. Poor regulation of dosage, irritation of pulmonary tract
bioavailability
fraction of dose available for biologic action. Measured by the area under the curve for the oral dose form vs. the IV dose form
limiting step for oral drugs
usually dissolution
factors affecting absorption in enteral drugs
form of drug, food in stomach, illness, blood flow
factors affecting absorption in parenteral drugs
blood flow, head, cold, illness. Form of drug
