Biomedical Engineering Reference
In-Depth Information
enhancers. Many papers have been published on the use and efficacy of a large num-
ber of absorption enhancers for nasal peptide and protein delivery to increase nasal
absorption [123 - 125] . Absorption enhancers may be required when a drug exhibits
poor membrane permeability, large molecular size, and enzymatic degradation by ami-
nopeptidases. The ideal properties of enhancer are that it should be effective in small
quantity, nonirritating, and nontoxic; its effect should be temporary and reversible; and
it should be compatible with other excipients and should not cause permanent dam-
age or alteration to the tissue. Absorption enhancers are usually classified as physi-
cal and chemical enhancers. Chemical enhancers act by destructing the nasal mucosa,
very often in an irreversible way, whereas physical enhancers affect nasal clearance
reversibly by forming a gel. Examples of chemical enhancers are bile acid salts, che-
lating agents, fatty acids, surfactants, and preservatives. The incorporation of absorp-
tion enhancers in nasal formulation may increase bioavailability.
9.5.4.2 Prolonging Contact Time with the Nasal Cavity
As discussed earlier in this chapter, either by using bioadhesive materials or by
increasing the viscosity of the formulation, rapid removal of material from the absorp-
tion site can be prevented, thereby prolonging the contact time of the formulation
with the nasal mucosal membranes. If the compound is retained longer in the nasal
cavity, it may have an increased chance of crossing the mucosa, leading to enhanced
absorption.
9.5.5 Therapeutic Inhalation Aerosols
Different routes of administration may be used to achieve either systemic or local
delivery of proteins and peptides. For small therapeutic molecules, various routes
for drug administration are parenteral (intravenous, intramuscular, and subcutane-
ous), oral, nasal, ocular, transmucosal (buccal, vaginal, and rectal), and transdermal.
However, the routes of administration for proteins and peptides are limited because
of their large size and structure. Active ingredients administered via a delivery system
are only successful if they are delivered in a timely manner direct to the site of dis-
ease, with ease and convenience to the patient and the assurance of a quality product.
Advances in drug formulation and inhalation device design are creating new opportu-
nities for inhaled drug delivery as an alternative to oral and parenteral delivery meth-
ods. Much of the interest in pulmonary delivery of systemic drug therapies is focused
on chronic diseases and refractory conditions—aliments that require frequent drug
administration for a specific period of time. The role of device design and develop-
ment in defining and driving emerging opportunities in this area cannot be overstated.
Inhalation aerosols are a system of finely divided liquid or solid particles dispersed in
and surrounded by a gas (fine suspensions or dispersions of solid particles in a gas),
intended to deliver drugs into the respiratory tract and both the central and peripheral
zones of the lung. There, significant retention and systemic absorption of the active
component occur, by inhalation or by breathing, using different pulmonary drug deliv-
eries ( Fig. 9.3 ).
Search WWH ::




Custom Search