Pharmacokinetic properties differences between

Pharmacokinetics PO/PR/IM/IV. Well absorbed orally. Give IM only if patient cant take orally. Give IV slowly because of fall in blood pressure. Barbiturates vary markedly in lipid solubility and plasma protein binding (Table 3.86). Barbiturates induce P450 enzymes in the liver which T metabolism of phenytoin, digitoxin, coumadin and others. Pharmacokinetics Primary difference between various benzodiazepine agonists are their pharmacokinetic properties (Table 3.8C). 

At the cellular level, the various types of receptor, transporter, enzyme and ion charmel are all chiral in form. Thus although the enantiomers of a drug may have identical physicochemical properties, the way in which they may interact with chiral targets at the level of the cell will give rise to different pharmacod)mamic and pharmacokinetic properties. A few simple examples will illustrate how taste and olfactory receptors can differentiate between enantiomers. Thus R-carvone tastes like spearmint whereas the S-isomer tastes like caraway. Similarly, R-limolene smells like lemon whereas the S-enantiomer tastes of orange. 

Much of the inter-species variation in pharmacokinetic properties can be explained as a consequence of body size (allometry). Consequently it is possible to scale pharmacokinetic parameters to the organism s individual anatomy, biochemistry and/or physiology in such a manner that differences between species are nuUified. Several excellent reviews on allometric scaling are available in the literature [2-7]. Allometric relationships can be described by an equation of the general form ... 

Chinese hamster ovary (CHO) cells and baby hamster kidney (BHK) cell lines have been most commonly used, in addition to other cell lines, such as various mouse carcinoma cell lines. The recombinant factor VIII product generally contains only VIILC (i.e. is devoid of vWF). However, both clinical and pre-clinical studies have shown that administration of this product to patients suffering from haemophilia A is equally as effective as administering blood-derived factor VIII complex. The recombinant VIILC product appears to bind plasma vWF with equal affinity to native VIILC, upon its injection into the patient s circulatory system. Animal and human pharmacokinetic data reveal no significant difference between the properties of recombinant and native products. 

Two different aspects have to be considered in the answer economic and scientific. An economic interest to have a variety of products in the market exists on the part of those pharmaceutical companies that have developed and marketed or are developing antipsychotics. Consequently, their advertising places the emphasis on the special features and advantages of individual medications, even though the differences between many products are not always very relevant clinically. Nevertheless, the differences that actually exist between products with regard to their pharmacokinetic and pharmacodynamic properties are of scientific interest, especially those related to the effects of atypical versus typical antipsychotics ... 

The straightforward step used to form the ring system means that the chemistry involved in the preparation of the scores of barbiturates that have been used clinically in fact devolves on the syntheses of the various malonic esters. It should be noted that little success has been achieved in changing the side effect spectrum of these dmgs. The main differences between the various agents involve their pharmacokinetic properties these in turn are manifested as variations in bioavailablity by parenteral and oral routes as well as in time to the onset and duration of action. 

Losartan was the first ATI antagonist to be used clinically. It has a complicated effect, since its major metabolite (E-3174) is about ten times more potent as an inhibitor of angiotensin II than losartan itself. Candesartan cilexetil is the only compound in this group which is a real prodrug. It is hydrolysed by the liver to the active form, candesartan. Differences between drugs in this class are largely accounted for by their pharmacokinetic properties (Table 8.2). 

The actions of acetylcholine released from autonomic and somatic motor nerves are terminated by enzymatic hydrolysis of the molecule. Hydrolysis is accomplished by the action of acetylcholinesterase, which is present in high concentrations in cholinergic synapses. The indirect-acting cholinomimetics have their primary effect at the active site of this enzyme, although some also have direct actions at nicotinic receptors. The chief differences between members of the group are chemical and pharmacokinetic—their pharmacodynamic properties are almost identical. 

The pharmacokinetic properties of the microemulsion were compared with those of the standard formulation in 39 liver-transplanted patients. AUC and Cmax values were significantly increased, and tmax was decreased following the microemulsion formulation, in both fasted and postprandial state. Differences between the microemulsion and the regular formulation in the fasting state and after high-fat meal, respectively, were +64% and +38% for AUC, +119% and +53% for Cmax, and -21% and —59% for tmax [43]. 

The pharmacokinetic properties of the benzodiazepines in part determine their clinical use. In general, the drugs are well absorbed, widely distributed, and extensively metabolized, with many active metabolites. The rate of distribution of benzodiazepines within the body is different from that of other antiseizure drugs. Diazepam and lorazepam in particular are rapidly and extensively distributed to the tissues, with volumes of distribution between 1 L/kg and 3 L/kg. The onset of action is very rapid. Total body clearances of the parent drug and its metabolites are low, corresponding to half-lives of 20-40 hours. 

The differences between low molecular weight Gd-based CAs and macromolecular CAs stem mainly from their pharmacodynamic and pharmacokinetic properties, that is, what the CA does to the body, and vice versa. In addition to the observed relaxivity, the dynamic relaxivity is another parameter that is used in contrast-enhanced MRA in the presence of different types of CAs. The dynamic relaxivity describes the relaxivity results from both bound and non-bound complexes. For example, a comparison of the strongly HSA-bound MS-325 with the non-HSA-bound P792 in rabbit showed P792 to have a more constant dynamic relaxivity [114], A constant pharmacokinetics profile is also favorable for MRA analysis. 

In general, NSAIDs share a number of different pharmacokinetic properties. For example, most, but not all, have relatively short plasma half-lives. Meclofenamic acid and ketoprofen, for example, have plasma half-lives of l-2h in the horse (Owens et al 1995a, Snow et al 1981). Phenylbutazone has a more variable plasma half-life but it is usually determined to be less than 8h (Lees Higgins 1985). In contrast, the plasma half-life of carprofen is between 18 and 21 h in the horse (Lees et al 1994, McKellar et al 1991). 

The main difference between prazosin, terazosin, and doxazosin lies in their pharmacokinetic properties. As men-lloncd above, these differences are dictated by the nature of the acyl moiety attached to the piperazine ring. A comparison of these three agents with respect to their oral bioavailability, half-life, and duration of action is shown in Table 16-2. These drugs are metabolized extensively, with the me-taNiies excreted in the bile. 

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