Tolerance continued types

The other three types of tolerance (pharmacokinetic, pharmacodynamic, and learned) are clubbed as acquired tolerance. In contrast to innate tolerance, this type of tolerance develops with continued opioid administration, and thus represents true tolerance rather than genetically mediated lack of sensitivity to opioids. 

In selec ting the machines of choice, the use of specific speed and diameter best describe the flow. Figure 10-67 shows the characteristics of the three types of compressors. Other considerations in chemical plant service such as problems with gases which may be corrosive or have abrasive solids in suspension must be dealt with. Gases at elevated temperatures may create a potential explosion hazard, while air at the same temperatures may be handled qmte normally minute amounts of lubricating oil or water may contaminate the process gas and so may not be permissible, and for continuous-process use, a high degree of equipment rehability is required, since frequent shutdowns for inspec tion or maintenance cannot be tolerated. 

Creep modeling A stress-strain diagram is a significant source of data for a material. In metals, for example, most of the needed data for mechanical property considerations are obtained from a stress-strain diagram. In plastic, however, the viscoelasticity causes an initial deformation at a specific load and temperature and is followed by a continuous increase in strain under identical test conditions until the product is either dimensionally out of tolerance or fails in rupture as a result of excessive deformation. This type of an occurrence can be explained with the aid of the Maxwell model shown in Fig. 2-24. 

The methods of control include selection for resistance or field tolerance and Manis has announced excellent clones of this type that, remarkably enough, include resistance to both Phytophthora and Dothidella. The other control is by fungicides. Of several sprays tried, Dithane with sticker gave best results. Under usual moist weather conditions, applications are put on at 8-day intervals. During the more severe rainy season it is necessary to spray as often as twice a week. However, when continuous rainfall occurred for 10 days or more without cessation, and no spraying was possible, Phytophthora damage increased, and it was a struggle to get the disease under control when less difficult conditions returned. 

BaselgaJ, HerbstR, LoRussoP, etal. Continuous administration of ZD 1839 (Iressa), a novel epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI), in patients with five selected tumor types evidence of activity and good tolerability. ProcAm Soc Clin Oncol 2000 19 177 (abstr). 

It must also be noted that an inducer may enhance not only the metabolism of other drugs but also its own metabolism. Thus, continued use of some drugs may result in a pharmacokinetic type of tolerance—progressively reduced therapeutic effectiveness due to enhancement of their own metabolism. 

Acetazolamide is a diuretic whose main action is the inhibition of carbonic anhydrase (see Chapter 15). Mild acidosis in the brain may be the mechanism by which the drug exerts its antiseizure activity alternatively, the depolarizing action of bicarbonate ions moving out of neurons via GABA receptor ion channels may be diminished by carbonic anhydrase inhibition. Acetazolamide has been used for all types of seizures but is severely limited by the rapid development of tolerance, with return of seizures usually within a few weeks. The drug may have a special role in epileptic women who experience seizure exacerbations at the time of menses seizure control may be improved and tolerance may not develop because the drug is not administered continuously. The usual dosage is approximately 10 mg/kg/d to a maximum of 1000 mg/d. 

The development of physical dependence is an invariable accompaniment of tolerance to repeated administration of an opioid of the - type. Failure to continue administering the drug results in a characteristic withdrawal or abstinence syndrome that reflects an exaggerated rebound from the acute pharmacologic effects of the opioid. 

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