Exam 1 Flashcards
deliver a drug to the body at a predetermined rate, increase the duration of drug action and decrease the frequency of dosing (enhance compliance), reduce or eliminate adverse effects, provide a uniform constant plasma drug concentration, avoid the peaks and troughs for improved therapeutic outcome
why modified release formulations
this drug is a rapid acting vasodilator, immediate release form causes significant and sudden reduction in BP, increased sympathetic outflow means increased HR and forcer contraction due to sudden drop, increase cardiac oxygen demand, if coronary blood flow does not increase than ischemia and necrosis can occur
why an immediate release form of nifedipine can potentially cause myocardial infarction
what should be the release kinetics (first or zero order) to provide a constant plasma drug level?
Zero order (constant amount of drug, replacing what is eliminated by body so amount of drug in body is constant)
to achieve a constant plasma drug level what should be the rate-limiting step (slowest step), drug release or drug absorption?
drug release, for a drug to be a good candidate its absorption should be fast because if slow is doesn’t matter if release is fast of slow because drug will just sit there
- dose-dumping (when modified dosage form releases all of its contents at once, everything gets released, contains more drug than immediate, can produce a high toxic level if chewed/released all at once)
- mistakenly exchange immediate release formulations with modified release formulations or vice versa
- less flexibility in dose adjustments (predetermined rate)
- formulation challenges, not suitable for all drugs
- problematic for patients with preexisting GI conditions for oral products like this (GI narrowing, shortened bowel, bariatric surgery)
limitations to modified release products
what type of modified drug release is monolithic (meaning the whole tablet is uniform)?
matrix systems
what type of modified drug release has different regions of the dosage form?
reservoir systems
mechanism of drug release: dissolution or erosion of matrix
example is niacin extended release tablets (antilipemic agent), polygel controlled release delivery system
hydrophilic matrix: soluble
patient counseling points:
- tablets come in 250mg, 500mg, 750mg scored, can be broken because monolithic but do not crush/chew
- long-acting forms reduce adverse effects of this drug including GI disorders, cough, skin rash, flushing
- tablets should be taken after a low-fat snack and cold water at bedtime because flushing will most likely occur during sleep
- also available in other dosage forms, should not substitute because they aren’t all the same
niacin ER tablets (Slo-Niacin)
mechanism of drug release: swelling of the matrix (depends on how fast or slow the matrix swells), dissolution and diffusion of drug through swollen gel layer
hydrophilic matrix: swellable
mechanism of drug release: dissolution and diffusion of drug through insoluble matrix
example: potassium chloride ER tablets (reduce the local adverse effect of KCl in GI tract
hydrophobic (insoluble) matrix
tablets:
K-tab and Klor-Con (wax matrix tablets)
Klor-Con M10, M15, M20 (microencapsulated potassium chloride)
capsule:
generic comes in 8 or 10 mEq, sprinkles
Counseling points:
- oral dosage forms should be taken with meals and a full glass of water or other liquid to minimize the risk of GI irritation (ER tabs reduce likelihood of producing high localized concentrations of potassium in GIT)
potassium chloride ER products
will draw in water, it will dissolve and create a channel, it is a water-soluble channeling agents, this affects drug release because increased this means increase channels for increased release rate
PEG
what are tablets called that appear in the stool after administration because they have a wax layer on the outside (Klor-Con, not Klor-Con M because M has wax at a micro level so not big enough to see in stool)?
ghost tablets
mechanism of drug release: drug dissolves out and then diffuses through a membrane (membrane still allows drug to come out, can’t break tabs because will release lots of drug at once)
example: felodipine ER coated tablet (calcium antagonist, rapid-acting vasodilator, lowers the risk of myocardial infarction)
reservoir system
tablet core: matrix system
membrane coating: wax that creates membrane, PEG (pore forming agent)
Felodipine ER tabs
what does OROS stand for?
osmotic-controlled release oral delivery system
mechanism of drug release: solvent-activated push, very controlled laser drills hole that has to be same size every time, drug release ultimately depends on size of hole, zero order constant amount of drug, semipermeable but rigid membrane
OROS
OROS example that should be swallowed whole, not crushed, split, or chewed
Procardia XL (nifedipine)
which system is dose dumping more likely to occur with (matrix or reservoir)?
reservoir
- dosage form that releases a discrete portion or portions of the drug at a time other than promptly after administration
- enteric coated dosage forms are an example of this (reduce stomach irritation like in aspirin, protect the drug from the acidic environment of the stomach like omeprazole, provide local action in the intestine/site of action like bisacodyl, prevent regurgitation and irritation of the esophagus like risedronate which is highly irritant)
- colon targeted drug delivery to treat problems in the colon, don’t want drug release in the stomach
delayed release dosage forms
- coated microbeads, granules, pellets
- Coreg CR (carvedilol) ER capsule is for heart failure and hypertension, it’s like giving two doses one IR and one CR, capsules should not be crushed, chewed, or divided but contents of capsule can be sprinkled on applesauce for IR
- ConZip (tramadol) ER capsule - capsule has a tablet (IR) and beads (ER) inside it to provide this effect
repeat action - biphasic
Concerta (methylphenidate) ER tablet for ADHD, elimination of this drug is about 3.5 hours (the IR tab is given every 4 hours/TID), OROS system, tablets should not be chewed, divided, crushed, ghost pill, drug overcoat gives first IR phase of release then inside is released in two phases
repeat action - triphasic
Claritin D 12 or 24 hour: outer layer is IR with loratadine and pseudoephedrine, core is ER with just pseudoephedrine (core is larger because need more excipients for ER)
repeat action - multilayer tablets