Salicylsalicylic acid revisited: a multicentre study

Absorption, biotransformation, and pharmacokinetics of salicylsalicylic acid in humans

The absorption, biotransformation, and pharmacokinetics of the antiinflammatory drug salicylsalicylic acid (SSA) were studied. Healthy adult males received 1000 mg SSA and 1300 mg aspirin according to a crossover design either as a single oral dose (12 subjects) or three times a day for five days (4 subjects). A newly developed, high-pressure liquid chromatographic assay permitted selective, direct measurement of SSA in the presence of high concentrations of salicylic acid, one of its metabolites. Following a single dose, SSA was promptly absorbed (mean time to peak level 1.5 hour) and was eliminated from plasma with a mean half-life of 1.1 hour. Less than 1 per cent was excreted in the urine as unchanged SSA. SSA did not accumulate in the plasma during multiple dosing. Plasma levels of salicylic acid following single and multiple doses of SSA indicate that SSA is extensively hydrolyzed to salicylic acid in the body. The slightly lower levels of salicylic acid after SSA than after aspirin may reflect direct biotransformation of some of the SSA to an SSA conjugate, without hydrolysis to salicylic acid.

High-pressure liquid chromatographic determination of salicylsalicylic acid, aspirin, and salicylic acid in human plasma and urine

A high-pressure liquid chromatographic method was developed for the separation and quantitation of salicylsalicylic acid (I), aspirin (II), and salicylic acid (III) in human plasma and urine. The method for plasma involves the selective extraction of I--III and an internal standard, alpha-phenylcinnamic acid, into methylene chloride from acidified plasma, followed by evaporation of the organic phase and dissolution of the residue in methanol. A 25-microliter aliquot is analyzed on a reversed-phase column with UV detection. Urine is treated similarly with hexane as the extracting solvent. If 300 nm is used as the monitoring wavelength, the assays of I and III are linear over the concentration range of 1--150 microgram/ml in both plasma and urine. If 280 nm is used as the monitoring wavelength, II can be quantitated along with I and III; however, detector sensitivities of I and III are two to three times greater at 300 nm. The accuracy and precision of the methods for I--III are adequate for clinical pharmacokinetic studies. Following therapeutic doses of I in humans, the method was applied successfully to the determination of I and III in plasma and urine.

Long-term management of rheumatoid arthritis with disalcid

Disalcid, a salicylic acid pro-drug, was administered for 3 months to eighteen rheumatoid arthritis patients, with monitoring of clinical response, side-effects and laboratory changes. The drug produced a satisfactory to excellent response in fourteen patients and was unsatisfactory in four. Gastric side-effects occurred in three patients and allergic reaction in one. Serum salicylic acid concentrations were adequately maintained between 15 to 25 mg/100 ml. Funduscopic monitoring revealed one retinal defect in a patient with hypertension. Laboratory examinations, blood chemistry and urine analyses remained within normal limits during the 12-week trial.