Pharmacokinetics active diffusion

Because of its pharmacokinetic features (pronounced bioaccessability upon oral use, diffusion to tissues and permeation into them, broad spectrum of antibacterial activity, and so on), fluoroquinolones have considerable potential for treating infections of practically any anatomic localization. Fluoroquinolones are very effective in treating infections of the respiratory tract, urinary tract, bones, skin, soft tissues, and so on. 

Mechanism of Action Clioquinol is a broad-spectrum antibacterial agent but the mechanism of action is unknown. Hydrocortisone is a corticosteroid that diffuses across cell membranes, forms complexes with specific receptors and further binds to DNA and stimulates transcription of mRNA (messenger RNA) and subsequent protein synthesis of various enzymes thought to be ultimately responsible for the anti-inflammatory effects of corticosteroids applied topically to the skin Therapeutic Effect Alters membrane function and produces antibacterial activity Pharmacokinetics Clioquinol may be absorbed through the skin in sufficient amounts. 

Chemical clastogenesis and mutagenesis both involve a complex series of processes, including pharmacokinetic mechanisms (uptake, transport, diffusion, excretion), metabolic activation and inactivation, production of DNA lesions and their incomplete repair or misrepair, and steps leading to the subsequent expression of mutations in surviving cells or individuals (Thble 7.1). Each of the steps in these processes might conceivably involve first order kinetics at low doses (e.g., diffusion, MichaeUs-Menten enzyme kinetics) and hence be linear. In principle, therefore, the overall process edso might be linear and without threshold. 

Moxifloxacin has excellent pharmacokinetics, is well-tolerated, nonphototoxic, and penetrates rapidly into the body tissues and fluids. Its powerful bactericidal activity and rapid tissue penetration and diffusion to the site of infection produce a rapid onset of action. Due to its long plasma half-life of 12 h, a once-daily dose of400 mg is sufficient for treatment. 

The different chemical solutions to solubilizing problems discussed in this chapter reveal that in many cases the chemical transformation used also improves the activity profile of the parent molecule. This can be due to purely pharmacokinetic factors such as a better resorption from the organism and faster transport and diffusion. These factors explain also why solubilized drugs are generally faster eliminated and therefore show fewer symptoms of toxicity. But the pharmacological profile also can be affected. Chlorpromazine, for example (Figure 38.26), has neuroleptic properties, whereas the parent phenothi-azine possesses anthelminthic properties. In this example, the attachment of the basic moiety has totally modified the pharmacological profile. However, the replacement of the basic moiety by its carboxylic counterpart yielded a compound totally inactive as neuroleptic (C. G. Wermuth, unpublished result). 

The pharmacokinetics of propofol are summarized in Table 13-2. Propofol s duration q/ier infusion (shorter than that of thiopental) can be explained by its very high clearance, coupled with the slow diffusion of drug from the peripheral to the central compartment. The rapid clearance of propofol explains its less severe hangover compared with barbiturates and may allow for a more rapid discharge from the recovery room. Propofol is metabolized in the liver to less active metabolites that are renally excreted Propofol is highly protein bound, and its pharmacokinetics, like those of the barbiturates, may be affected by conditions that alter serum protein levels. 

Generally, pharmacological treatment of diseases in the eye is limited by special pharmacokinetic properties inherent in the anatomy of the eye. Diseases in the anterior segment of the eye are predominantly treated by local application of the active compound in the conjunctiva These drugs will diffuse into the eye to affect the vitreous body and the retina, but for practical purposes this mode of administration is less suitable for diseases in the posterior segment of the eye. The vitreous body is avascular, which implies that the treatment of diseases in and around this structure depends on intravitreal injection of the active compound. On the contrary, the retina is richly vascularized, but the access to this structure of drugs administered through the systemic circulation is... 

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