Pharmaceutical Drugs and Dosage: Drug delivery systems - Review questions answers
Review questions
14.1 The
solution instilled as eye drops into the ocular cavity may disap-pear from the
precorneal area of the eye by which of the following route(s):
A. Nasolacrimal
drainage
B. Tear turnover
C. Corneal absorption
D. Conjunctival uptake
14.2 After
oral drug delivery, drugs are absorbed in the gastrointestinal tract, and through the
portal circulation, they enter the liver, where they are destroyed by
so-called:
A. Second-pass
metabolism
B. Drug efflux
metabolism
C. First-pass
metabolism
D. Drug decomposition
E. None of the above
14.3 The
lung:
A. Has a highly
permeable membrane
B. Has a membrane that
provides an effective barrier to drug absorption
C. Provides easy access
to the bloodstream
D. None of the above
14.4 Which
layer is the major rate-limiting barrier for permeation of hydro-philic drugs
across the cornea?
A. Endothelial layer
B. Stroma
C. Epithelial layer
D. A and C
14.5 Liposomes
containing an anticancer drug are rapidly taken up by the cells of
reticuloendothelial system on systemic administration. How can one extend the
blood circulation time of this liposomal system?
14.6 Define
polymeric micelles and liposomes. What is a common feature of these two carrier
systems?
14.7 Why oral
delivery of protein and peptide drugs is often not preferable?
14.8 How can
a matrix system be differentiated from a reservoir system?
14.9 What are
Peyer’s patches? How can they be exploited in drug delivery and targeting?
Answers:
14.1 E.
14.2 C.
14.3 A.
14.4 D.
14.5 PEGylation
or reduction in size increases the retention time of lipo-somes in the
bloodstream. Inclusion of PEG-lipid conjugates, such as polyethylene
glycol–phosphatidylethanolamine (PEG–PE) reduces the uptake of liposomes by
cells of the reticuloendothelial systems (RES), leading to their prolonged
circulation half-life.
14.6 Polymeric micelles are small spherical
structures composed of both hydrophilic
and hydrophobic groups. The micelles are in dynamic equilibrium with free
molecules (monomers) in solution; that is, the micelles are continuously
breaking down and reforming. This fact distinguishes micellar solutions from
liposomes, which are micro-scopic phospholipid vesicles composed of uni- or
multilamellar lipid bilayers surrounding aqueous compartments.
14.7 The low
oral bioavailability of peptide and protein drugs is primar-ily due to their
large molecular size and vulnerability to proteolytic degradation in the GI
tract. Most protein and peptide drugs are sus-ceptible to rapid degradation by
digestive enzymes. Furthermore, most peptide and protein drugs are rather
hydrophilic and thus are poorly partitioned into epithelial cell membranes,
leading to their absorption across the GI tract through passive diffusion.
14.8 A microcapsule is a reservoir-type
system in which the drug is located centrally
within the particle, whereas a microsphere
is a matrix-type sys-tem in which the drug is dispersed throughout the
particle. Microcapsules usually release their drug at a constant rate
(zero-order release), whereas microspheres typically give a first-order release
of drugs.
14.9 Peyer’s patches belong to gut-associated lymphoid tissues (GALT) of the small intestine.
Peyer’s patches are capable of internalizing particu-late matter, bacteria, and
marker proteins. Localization of mucoadhe-sive polymeric delivery systems at or
around Peyer’s patches has the potential of favoring the absorption of peptides
and proteins.
Related Topics
TH 2019 - 2023 pharmacy180.com; Developed by Therithal info.