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Dose dependentd

Effective concentrations (mg/ml or mM)

See salicylate

50 to >200 (0.5 to >1.0mM)

Toxic concentrations (mg/ml or mM)

See salicylate

>200 (>1mM)

^Dependent on dose and pH of urine.

b95% at 14 g/ml, further decrease at higher doses.

c~0.2hat300g/ml.

h at 300 mg to 20 h and more in intoxication.

^Dependent on dose and pH of urine.

b95% at 14 g/ml, further decrease at higher doses.

c~0.2hat300g/ml.

h at 300 mg to 20 h and more in intoxication.

Figure 2.7 Accumulation of salicylate in healthy adults within 1 week after oral intake of 0.5 or 1 g aspirin in 8 h intervals (modified after [1]).

2.1.2.3 Excretion of Salicylates

The elimination of aspirin occurs completely (>98%) as salicylic acid and salicylic acid metabolites in urine. As mentioned above, the composition of the spectrum of metabolites is dependent on the aspirin dose. The absorption/secretion balance within the kidney tubules depends on the pH of tubulus fluid: alkalinization of the urine stimulates the dissociation of the acid(s) and increases the excretion of salicylate (metabolites) 5-10-fold. This effect can be used therapeutically in the treatment of salicylate poisoning (Section 3.1.1).

At an analgesic dose of 1.5 g aspirin, the approximate recovery rates of salicylates in urine are as

Table 2.4 Metabolites of aspirin (salicylic acid) recovered in the urine after intake of therapeutic or toxic doses.

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