Salicylate measurement: clinical usefulness and methodology

Urine Trinder spot test: a rapid salicylate screen for the emergency department

STUDY OBJECTIVE

To determine whether the urine Trinder spot test, performed by emergency physicians, is a sensitive bedside screen for salicylates.

DESIGN

Prospective, blinded human protocol with subjects serving as their own controls.

SETTING

Urban Level I medical center.

PARTICIPANTS

Ten male and two female volunteers with negative urine toxicologic screen results before the start of the study.

INTERVENTIONS

Each participant ingested 975 mg of nonenteric coated aspirin. Serum and urine samples were collected before ingestion and 2 and 4 hours after ingestion. Three emergency physicians and a toxicology technician independently performed Trinder spot tests. Results were recorded as positive or negative for salicylate on the basis of color change (a purple reading was considered positive).

RESULTS

All postingestion urine specimens were detected by all testers with 100% sensitivity. Two false positives occurred in the preingestion samples. Serum quantitative assays confirmed the presence of salicylates in all postingestion specimens.

CONCLUSION

This pilot study suggests that emergency physicians can use the Trinder spot test as a sensitive bedside salicylate screen, potentially saving time and quantitative assay expense.

Investigation of the influence of acetylsalicylic acid on the steady state of long-term therapy with theophylline in elderly male patients with normal renal function

The risk inherent in the clinical control of patients with theophylline is widely recognized. Elderly patients may present an additional risk because of altered pharmacokinetics and the use of concomitant medication. Acetylsalicylic acid has been proposed for primary and secondary prevention of myocardial infarction and possible strokes. This investigation was undertaken to determine if concomitant administration of acetylsalicylic acid in elderly patients would alter steady-state levels of theophylline. A population of smoking male patients older than 60 years of age under long-term control of chronic obstructive pulmonary disease (COPD) with theophylline were evaluated for a baseline period of 3 days. Serum levels were measured at 6:00 AM and 6:00 PM. An enteric-coated acetylsalicylic acid preparation, 650 mg by mouth, was added to the daily slow-release theophylline, 6:00 AM hour dose regimen for 4 weeks. The serum levels of theophylline and salicylates were measured at 6:00 PM after dosing and at 6:00 AM the following day, at weekly intervals for 4 weeks. Urine specimens collected before administration of medication at 6:00 AM were analyzed for salicylates to further confirm dosage compliance. All volunteers continued to be clinically controlled throughout the treatment period and no symptoms of either overdose or underdose of either medication occurred. Plateau or trough theophylline serum levels did not change significantly during the salicylate treatment period. Salicylate serum levels did show during treatment self-induced metabolism. It is concluded that in elderly male patients, a daily concomitant therapeutic salicylate regimen does not alter steady-state serum theophylline levels and therefore does not per se necessitate the assay of theophylline blood levels in elderly patients.

Reduction of capsular polysaccharide production in Klebsiella pneumoniae by sodium salicylate

Heavily encapsulated Klebsiella pneumoniae (serotypes 1 and 2) was cultured in the presence of sodium salicylate. The addition of salicylate (2 to 30 micrograms/ml) progressively decreased the amount of capsular polysaccharide produced by all strains without significantly inhibiting cell growth. Further addition of salicylate (50 to 200 micrograms/ml) was progressively inhibitory to cell growth and decreased the production of polysaccharide only slightly. The optimal concentration of salicylate that could reduce the polysaccharide production of heavily encapsulated, virulent strains by 50% or more was 30 micrograms/ml. Mutants of these bacteria that produced less capsule were affected by salicylate to a lesser degree. All concentrations of salicylate tested were physiologically achievable in humans and within the therapeutic range of aspirin. The addition of calcium and magnesium partially reversed the effects of salicylate on polysaccharide production. Chelating agents, particularly EGTA [ethylene-bis(oxyethylenenitrile)tetraacetic acid], reduce capsule production as salicylate did. Thus, the chelation of calcium and magnesium by salicylate could account, at least in part, for the reduction of capsule. Optical density measurements allowed for rapid monitoring of capsule production in various culture media because a large part of culture turbidity was apparently due to the capsule. Decreased production of the primary K. pneumoniae virulence factor with salicylate may have therapeutic potential.