Pharmacokinetics administration

Pharmacology Lincomycin and clindamycin, known collectively as lincosamides, bind exclusively to the 50 S subunit of bacterial ribosomes and suppress protein synthesis. Cross-resistance has been demonstrated between these 2 agents. Clindamycin is preferred because it is better absorbed and more potent. Pharmacokinetics Administration with food markedly impairs lincomycin (but not clindamycin) oral absorption. 

Pharmacokinetics Administration can be by an intravenous, oral, or topical route. The efficacy of topical applications is doubtful. The drug distributes well throughout the body, including the cerebrospinal fluid. Acyclovir is partially metabolized to an inactive product. Excretion into the urine occurs both by glomerular filtration and tubular secretion. Acyclovir accumulates in patients with renal failure. 

Furthermore, pharmacokinetic administration, distribution, metabolism and excretion (ADME) factors affect drug bioavailability, efficacy and safety, and, thus, are a vital consideration in the selection process of oral drug candidates in development pipelines. Since solubility, permeability, and the fraction of dose absorbed are fundamental BCS parameters that affect ADME, these BCS parameters should prove useful in drug discovery and development. In particular, the classification can used to make the development process more efficient.For example, in the case of a drug placed in BCS Class II where dissolution is the rate-limiting step to absorption, formulation principles such as polymorph selection, salt selection, complex formation, and particle size reduction (i.e., nanoparticles) could be applied earlier in development to improve bioavailability. 

This wide range of pharmacokinetic properties, along with thek ease of administration, broad spectmm antimicrobial activity, and noninterference with host-defense mechanisms is responsible for thek widespread use five decades after thek discovery. 

The development of new antibiotics to combat resistance, and to provide easier oral administration and improved pharmacokinetics has been successful through synthetic modifications. This approach has been particularly rewarding in the area of P-lactams. The commercial importance of the P-lactams is evident from Table 3 which gives the market share of antibacterials. Fully 62% of the 1989 world antibacterial market belonged to the cephalosporin and penicillin P-lactams (20). 

A novel approach to the modification of aminoglycoside pharmacokinetics is under investigation (84). Administration of gentamicin encapsulated in egg phosphatidylcholine Hposomes has been found to lead to a longer half-life and much higher spleen and Hver levels for the gentamicin component. This formulation is undergoing clinical study (85). 

Muzolimine (710), a 1-substituted 2-pyrazolin-5-one derivative, is a highly active diuretic, differing from the structures of other diuretics since it contains neither a sulfonamide nor a carboxyl group. It has a saluretic effect similar to furosemide and acts in the proximal tubule and in the medullary portion of the ascending limb of the loop of Henle. Pharmacokinetic studies in dogs, healthy volunteers and in patients with renal insufficiency show that the compound is readily absorbed after oral administration (B-80MI40406). 

The separation of enantiomers is a very important topic to the pharmaceutical industry. It is well recognized that the biological activities and bioavailabilities of enantiomers often differ [1]. To further complicate matters, the pharmacokinetic profile of the racemate is often not just the sum of the profiles of the individual enantiomers. In many cases, one enantiomer has the desired pharmacological activity, whereas the other enantiomer may be responsible for undesirable side-effects. What often gets lost however is the fact that, in some cases, one enantiomer may be inert and, in many cases, both enantiomers may have therapeutic value, though not for the same disease state. It is also possible for one enantiomer to mediate the harmful effects of the other enantiomer. For instance, in the case of indacrinone, one enantiomer is a diuretic but causes uric acid retention, whereas the other enantiomer causes uric acid elimination. Thus, administration of a mixture of enantiomers, although not necessarily racemic, may have therapeutic value. 

The pharmacokinetics of azacitidine shows that it is rapidly absorbed after s.c. administration with the peak plasma concentration occurring after 0.5 h. The bioavailability of s.c. azacitidine relative to i.v. azacitidine is approximately 89%. Urinary excretion is the primary route of elimination of azacitidine and its metabolites. The mean elimination half-lives are about 4 h, regardless of i.v. or s.c. administration. 

Patients receiving cytotoxic chemotherapy very often need concomitant administrating of antiemetic therapy. Such protocols will start well in advance of administering the cytotoxic, and last for a reasonable time with regard to pharmacokinetics of the antineoplastic agent. In addition, side effects of antineoplastic therapy are made better tolerable by supportive care. 

Marketing Extension Application (change in active substance, bioavailability, pharmacokinetics, strength, pharmaceutical form or route of administration, if... 

Lack of information concerning pharmacokinetics and bioavailabihty after p.o. and parenteral administration of the polymers. 

A monograph on the larch arabinogalactan has been published, containing pharmacokinetics, clinical indications, the lack of side-effects and dosage [60]. In a report from 2003, the effect over time of in-vivo administration of the larch arabinogalactan on the immune and hemopoietic cell... 

Greenblatt DJ, Shader RI Long-term administration of benzodiazepines pharmacokinetic versus pharmacodynamic tolerance. Psychopharmacol Bull 22 416 23, 1986... 

Note Derivatization with this reagent sequence in combination with extraction and TLC separation is speciftc for amitriptyline and nortriptyline in the analysis of plasma furthermore its high sensitivity allows its employment in pharmacokinetic studies, e. g. after the oral administration of a single dose of 25 mg amitriptyline. 

A pro-drug approach for improving the pharmacokinetics of zanamivir has recently shown some promise. The alkoxyalkyl ester 23 of zanamivir, with long alkyl chains chosen to counteract the high hydrophUicity of the molecule, was reported to show significant protective effects against influenza (HlNl) infection in mice upon oral or intraperitoneal administration (Liu et al. 2007). 

Gupta PK, Ehrnebo M. 1979. Pharmacokinetics of alpha isomer and beta isomers of racemic endosulfan following intravenous administration in rabbits. Drug Metab Dispos 7 7-10. 

McMahon B.M., Mays D., Lipsky J., Stewart J.A., Fauq A., Richelson E. Pharmacokinetics and tissue distribution of a peptide nucleic acid after intravenous administration. Antisense Nucleic Acid Drug Dev. 2002 12 65-70... 

U.S. Department of Health and Human Services, Food and Drug Administration, Center for Drug Evaluation and Research (CDER) and Center for Biologies Evaluation and Research (CBER). Guidance for Industry Population Pharmacokinetics. http //www.fda.gov/cder/guidance/1852fnl.pdf (accessed October 1,... 

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