Pharmacology Flashcards
What aare adjacent corneocytes held together by?
corneodesmosomes
What is conventional transdermal drug delivery driven by?
diffusion
What is Fick’s Law?
Rate of absorption (flux) is equal to the permeability coefficient times the concentration of drug
What are the important factors in the role of the vehicle?
The solubility of the drug in vehicle (Cy)
Maximising the movement of the drug from vehicle to the atratum corneum (drug must escape from vehicle)
What is the permeability coefficient (Km) described as?
the equilibrium solubility of the drug in the stratum corneum realtive to its solubility in the vehicle
What is the purpose of excipients?
They are put into the vehicle to enhance the solubitliy of the drug and so enhance absorption
Why might excess, non-dissolved drug be included into transdermal patches?
increases duration of effectiveness nad porvides a constant rate of delivery- dissolved drug that is removed by absorption is replaced by undissolved drug maintaining a fairly constant soluble concentration
Why are topically applied drugs generally poorly absorbed?
only a small fraction partitions into the stratum corneum
Name some factors that can improve partitioning
hydration of the skin by occlusion (increases the reservoir with which the drug can be absorbed)
inclusion of excipients which also increase the solubility of hydrophobic drugs
What are the factors that affect the absorption of topically applied drugs in drug preparation?
drug conc. the drug salt (different salts can have varying potencies) the vehicle (can affect how active a drug is)
What do glucocorticoids combine with in the cytoplasm?
GRalpha
What does combination of steroid with GRalpha cause the dissociation of?
inhibitory heat shock proteins
they were previously joined to GRalpha but steroid kicks it out
What does the steroid and GRalpha do in the nucleus?
bind to the glucocorticoid response elements which switches on or off transcription of specific
Where is subcutaneous drug delivered?
adipose tissue just beneath teh surface of the skin
How does subcutaneous drug reach systemic circulation?
diffuses into capillaries or lymphatics
What are some advantages to subcut drug administration?
absorption is relatively slow (poor vascular supply)
can be used to introduce a depot of drug under the skin that is very slowly released into the circulation
What is an advantage of subcut drug administration?
injection volume is limited
What is the skin a good route for a systemic effect?
avoids first pass metabolism
drug absorption can be terminated rapidly
What makes a drug suitable for transdermal drug delivery?
low molecular weight
moderately lipophilic
potenet
relatively brief half life
What is iontophoresis
application of low voltage electrical pulses to the skin via a surface electrode over a prolonged period of time can drive low molecular mass molecules (of the same charge) through the skin- move away from the same charge
What is electroporation?
very brief high volatge pulses lead to “pore” formation
