Amount remaining to be excreted

ARE, amount remaining to be excreted. °This equals the bolus dose administered (A ) .=Ao. ... 

Fig. 6 Semilogarithmic plot of amount of drug remaining to be excreted (ARE) into urine, I) )/ — Du, versus time.

When sufficient urine samples have been collected to ensure that no significant amount of drug remains to be excreted, the cumulative urinary recovery is symbolized as The relative extent of absorption of... 

A plot of [(Xu) , - (Xu) J (i.e. the amount of drug remaining to be excreted, which also equals the amount of drug remaining in the blood) against time (Eq. 3.20) should provide a straight line on semilogarithmic paper, as illustrated in Fig. 3.17. 

Column 7 provides the values for the amount (mg) of drug remaining to be excreted (i.e. ARE or [(Xu) - (Xu)J) at each time interval. These values are obtained by subtracting the cumulative amount (mg) of drug excreted at each time interval (numbers reported in column 5) from the value of the cumulative amount of drug in the urine at time infinity (80 mg at 12 h or, in this example, the dose administered). It is important to note that the cumulative amount of drug (mg) excreted in urine (i.e. values reported in column 5)... 

Figure 3.21 Semilogarithmic plotof amount of drug remaining to be excreted (X ) (ARE method) versus time for data given in columns 6 and 7 of Table 3.3. K, elimination rate constant t)/2, elimination half life.

The preceding brief description of the nature and scope of biochemical and molecular toxicology should make clear that the study of toxic action is a many-faceted subject, covering all aspects from the initial environmental contact with a toxicant to its toxic endpoints and to its ultimate excretion back into the environment. A considerable amount of material is summarized in the chapters following, but many essentials still remain to be discovered. 

Some chemicals that are stored may remain in the body for years without exhibiting appreciable effects. One such chemical is DDT. Accumulation or buildup of free chemicals may be prevented until the storage sites are saturated. Selective storage limits the amount of foreign chemicals to be excreted, however. Since bound or stored toxicants are in equilibrium with their free forms, a chemical will be released from the storage site as it is metabolized or excreted. On the other hand, accumulation may result in illnesses which develop slowly, as exemplified by fluorosis and lead and cadmium poisoning. 

Cellular metabolism results in the production of large quantities of hydrogen that need to be excreted in order to maintain acid-base balance. In addition, small amounts of acid and alkali are also presented to the body through the diet. The bulk of acid production is in the form of CO2, from the metabolism of carbohydrates, proteins, and lipids. When respiratory function is normal, the amount of CO2 produced metabolically is equal to the amount lost by respiration, and the blood CO2 concentration remains constant. The average adult produces approximately 15,000 mmol of CO2 each day from the catabolism of carbohydrate, protein, and fat. ... 

Sodium balance is achieved when salt intake is equal to salt output. The intake of salt in the average American diet (10 to 15 g/day) far exceeds what is required physiologically. Only about 0.5 g/day of salt is lost in sweat and feces. The remaining ingested salt must be excreted in the urine. The amount of sodium excreted by the renal system is determined by ... 

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