Absorption enhancers types

Kitano M, Maitani Y, Takayama K, Nagai T (1998) Buccal absorption through golden hamster cheek pouch in vitro and in vivo of 17/f-estradiol from hydrogels containing three types of absorption enhancers. Int J Pharm 174 19-28... 

New Types of Absorption Enhancing Systems Used in Rectal Drug Administration... 

Watanabe, Y., et al. 1992. Absorption enhancement of polypeptide drugs by cyclodextrins. I. Enhanced rectal absorption of insulin from hollow-type suppositories containing insulin and cyclodextrins in rabbits. Chem Pharm Bull 40 3042. 

Matsumoto, Y., et al. 1989. Rectal absorption enhancement of gentamicin in rabbits from hollow type suppositories by sodium salicylate or sodium caprylate. Drug Des Deliv 4 247. 

Another type of absorption enhancer, which has been shown to have a better safety profile, is cyclodextrin (CD) [39]. CDs have been shown to form inclusion complexes with lipophilic drugs, thereby improving their aqueous solubility and stability. A powdered insulin formulation containing dimethyl-(3-cyclodextrin improved the absolute bioavailability of insulin by 13% in rabbits compared to a control liquid formulation (1%) of insulin with dimethyl-(3-cyclodextrin [40]. Recently, hydroxypropyl (3-cyclodextrin has been shown to be more effective for enhancing the nasal absorption of acyclovir than a range of other absorption enhancers in vivo [41]. 

Several peptide products used in the treatment of diabetes mellitus, in addition to insulin, are currently administered by subcutaneous injection and these drugs are candidates for development of nasal formulations. Glucagon-like peptide-1 (GLP-l)-related peptides stimulate the insulin response to glucose and diminish the release of glucagon after a meal. These effects diminish the excessive postprandial increase in glucose observed after a meal in persons with type 2 diabetes mellitus. GLP-1-related peptides must be administered by subcutaneous injection before meals in order to be effective. This requirement for injection before each meal is likely to impact the utilization of these products by persons with type 2 diabetes. Exendin-4 is a GLP-1-related peptide with a molecular mass of 4.2 kDa. The development of a GLP-1-related peptide nasal formulation containing an absorption enhancer would allow patients to scll-administer one of these drugs just before a meal without the need for a subcutaneous injection. 

Penetration enhancers are substances that can increase the absorption of a co-administered dmg, and include surfactants, bile salts, chelating agents, and fatty acids. Penetration enhancers are widely used in dmg delivery to potentiate absorption across various types of epithelia, including the epithelium of the gastrointestinal tract. However, a major limiting factor in the general acceptance of absorption enhancers for improving oral dmg absorption is the non-specific nature of their effects. 

Absorption can be enhanced via several mechanisms. These include increased membrane fluidity, chelation of the calcium ions that serve to maintain the dimension of the intercellular space, solubilization of the mucosal membrane, enhancement in water flux, and reduction of the viscosity of the mucus layer adhering to the epithelial cells. A discussion of various types of pentration enhancers and their mechanism (s) of action is given in Chapter 8 (Section 8.7.1). Table 6.4 summarises the oral absorption enhancers that have been tested for oral dmg delivery. 

Describe the types of absorption enhancers under development for use in vaginal route. 

Type of Compound (Absorption Enhancers) Examples Mechanism of Absorption Enhancement... 

Table 2 Some types of oral drug absorption enhancers Non-steroidal anti-inflammatory agents Surfactants Bile salts...

A recent article by Davis and Illum summarizes absorption enhancers based on their chemical classification, which is better suited than those based on the mechanism of their action. At present, there are 9 or 10 major types of nasal absorption-enhancing agents, as shown in Table 3. 

Conjugation of the alkyne units into the porphyrin or phthalocyanine backbone electronic structure leads to absorptivity enhancements and large red-shifts in their electronic spectra that have been sought for nonlinear optics, dyes, photonic materials, and photodynamic therapy types of applications. 

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