Bioavailability comparative

Recently, leaders in the pharmaceutical industry have developed a list of desired properties for a fourth generation of SERMs (Table 2). In general, future SERMs must oppose endogenous hormone action in the breast and reproductive system while displaying full estrogenic effects in the cardiovasculature, bone and central nervous systems. Additional criteria are that fourth generation compounds possess superior bioavailability compared with existing SERMs and have... 

Oral administration of arecoline is ineffective for clinical purposes due to first-pass metabolism (Hussain and Mollica 1991). The nasal route is an alternate possibility, with 85% bioavailability compared to intramuscular administration. 

Amprenavir oral solution was 14% less bioavailable compared to the capsules. 

C. Structural modification by placing the hydroxy groups at positions 3 and 5 of the phenyl ring has resulted in compounds that are not substrates for COMT, resulting in lower rates of metabolism and enhanced oral bioavailability compared to catecholamines. 

Neoral has increased bioavailability compared to Sandimmune (do NOT use interchangeably)... 

When delivered parentally or orally, a drug in solution is more rapidly bioavailable compared to a solid dosage form. The cosolvent approach also has some limitations as pointed out for other solubilization techniques. When solubilization of a drug is achieved by use of cosolvent, it must meet certain requirements, such as nontoxicity, compatibility with blood, nonsensitizing, nonirritating, and above all physically and chemically stable and inert. 

Carbacephems aOO 1 loracarbef ° N v Acl co2h improved chemical stability, longer half-life, better oral bioavailability compared to cefaclor... 

Leuprolide acetate, a highly potent synthetic analogue of LHRH, is a nonapeptide (5-oxo-Pro-His-Trp-Ser-Tyr-D-Leu-Leu-Arg-Pro-ethylamide acetate) with a molecular weight of -1200 Da. Leuprolide acetate has shown promise for the treatment of infertility, postmenopausal breast cancer, and prostate cancer. Very low oral bioavailability of leuprolide acetate has led to an interest in using the lung as a site for the systemic delivery of leuprolide. Okada et al. [70] have shown that a mixed micellar solution of leuprolide acetate has only 0.05 % oral bioavailability compared to IV leuprolide acetate. This low oral bioavailability may be attributed to poor membrane permeability as well as to significant enzymatic deactivation in the intestine. 

To overcome the limits of oral bioavailability of zanamivir, the development of second-generation zanamivir was pointed toward improving its pharmacokinetic properties. In this context, the most encouraging results were obtained with the phos-phonate analogue of zanamivir, with modification of the C7-hydroxy group or with a replacement of the glycerol side chain that also improved oral bioavailability compared to the original inhibitor 13 (Fig. 17.10). 

LLL tablets (Treatments B and C) provided lower Cmax values and lower relative bioavailability compared to the IR formulation (Treatment A). A longer half-life was observed for Treatment B (matrix tablets), under both fasting and non-fasting conditions, but for Treatment C (bilayer tablets) the lower limit of the 90 % confidence was above 100 % only under fasting conditions. 

Krauland et al. [93] prepared the microparticles with thiolated chitosan (chitosan-TBA chitosan-4-thiobutylamidine conjugate) intended for nasal peptide delivery. During the preparation process microparticles were stabilized by the formation of inter- and intramolecular cross-linking via disulfide bonds. Chitosan-TBA microparticles were characterized by improved swelling ability and displayed 3.5-fold higher insulin bioavailability compared to unmodified chitosan microparticles. 

Ferrous sulphate eneapsulated in soy lecithin liposomes has been used to deliver iron. These preparations have improved bioavailability compared to ferrous sulphate directly added in milk and dairy products (Boccio et al. 1997 Uicich et al. 1999). Albaldawi et al. (2005) reported that the addition of encapsulated haem iron in lecithin/cholesterol liposomes resulted in improved rheological properties of bread dough and the sensory properties of baked bread. 

Valacyclovir is an ester prodrug of acyclovir. It provides significantly better oral bioavailability compared to acyclovir. This advantage results in substantially higher serum acyclovir concentrations than is possible with oral acyclovir. In addition, fewer daily doses are required with valacyclovir (Curran and Noble, 2001). 

Uekama, K. Ikegami, K. Wang, Z. Horiuchi, Y. Hirayama, F. Inhibitory effect of 2-hydroxypropyl-beta-cyclodextrin on crystal growth of nifedipine during storage superior dissolution and oral bioavailability compared with polyvinylpyrrolidone K-30. J. Pharm. Pharmacol. 1992, 44 (2), 73-78. 

Pulmonary delivery of insulin for systemic absorption in the treatment of diabetes has been studied extensively since the early days of insulin discovery almost a century ago. Colthorpe et al. and Pillai et al. demonstrated in rabbit and monkey models, respectively, that the deeper into limg the dose of insulin was delivered, the higher was the bioavailability. The work of Laube, Benedict, and Dobs showed the need to achieve deep pulmonary deposition of this molecule for efficient absorption in humans. Handheld liquid and dry powder delivery systems have been developed to generate insulin-containing aerosols with the majority of the particles in the aerodynamic size range 1-3 pm. The relative bioavailability compared with subcutaneous injection based on the insulin contained in the dosage form was 110/ [52] powder system and for the aqueous-based... 

The structures of some prominent d,v-isomcrs of lycopene are shown in Figure 4.2. G. s-isomers have distinct physicochemical characteristics (and hence, bioactivity and bioavailability) compared to their all-trans counterparts. In general, the di-isomers are more soluble in oil and hydrocarbon solvents than their all-trans counterparts. They are less prone to crystallization because of their kinked structures. They also are less intense in color, which may influence the consumers perception of food quality. The appearance of a distinct absorption maximum in the UV region ( di-peak ) is useful for distinguishing between the different isomers. 

Noscapine (30) is a naturally occurring phthalideisoquino-line alkaloid obtained from opium that has weak anticancer properties. Subtle changes to the corresponding phenol (31) and aniline (32) resulted in a >50-fold increase in activity in an in vitro tubulin polymerization assay. Moreover, the phenol shows a modest 1.5-fold increase in oral bioavailability compared to noscapine (30). 

For IDA, IV iron, though costly, has superior bioavailability compared with oral preparations. In select individuals the bioavailability advantage of parenteral iron over oral iron can be the difference in the achievement of a successful outcome. The benefits of using combination oral iron products designed to enhance absorption is probably not warranted. 

Eye ointments are sterile semi-solid preparations intended for application to the conjunctiva. They are attractive because of their increased contact time and better bioavailability compared to solutions. They can be very useful for night-time application, However, they are not always well accepted by patients because upon application they often cause blurred vision. A wide variety of ointments are available commercially. 

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