High Doses Of Salicylate Research Articles

The Diagnostic Role of Stapedius Reflex Estimations

High dose of salicylate, the active ingredient in aspirin, has long been known to induce transient hearing loss, tinnitus and hyperacusis making it a powerful experimental tool. These salicylate-induced perceptual disturbances are associated with a massive reduction in the neural output of the cochlea. Paradoxically, the diminished neural output of the cochlea is accompanied by a dramatic increase in sound-evoked activity in the auditory cortex (AC) and several other parts of the central nervous system. Exactly where the increase in neural activity begins and builds up along the central auditory pathway are not fully understood. To address this issue, we measured sound-evoked neural activity in the cochlea, cochlear nucleus (CN), inferior colliculus (IC), and AC before and after administering a high dose of sodium salicylate (SS, 300 mg/kg). The SS-treatment abolished low-level sound-evoked responses along the auditory pathway resulting in a 20–30 dB threshold shift. While the neural output of the cochlea was substantially reduced at high intensities, the neural responses in the CN were only slightly reduced; those in the IC were nearly normal or slightly enhanced while those in the AC considerably enhanced, indicative of a progress increase in central gain. The SS-induced increase in central response in the IC and AC was frequency-dependent with the greatest increase occurring in the mid-frequency range the putative pitch of SS-induced tinnitus. This frequency-dependent hyperactivity appeared to result from shifts in the frequency receptive fields (FRF) such that the response areas of many FRF shifted/expanded toward the mid-frequencies. Our results suggest that the SS-induced threshold shift originates in the cochlea. In contrast, enhanced central gain is not localized to one region, but progressively builds up at successively higher stage of the auditory pathway either through a loss of inhibition and/or increased excitation.

Salicylate Hepatitis

Two patients developed acute hepatic injury as a result of salicylate therapy. In each patient serum salicylate levels were below 25 mg per 100 ml during the development of hepatic dysfunction. Liver biopsies, obtained a few days after the peak abnormalities in serum transaminases, revealed nonspecific acute hepatitis. Normal liver tissue was found before the beginning of salicylate treatment in 1 patient, who had systemic lupus erythematosus and drug rechallenge was not attempted. In the other patient, who had rheumatoid arthritis, rechallenge with salicylate evoked hepatic dysfunction and recurrent symptoms. Salicylate-induced liver injury should be considered in the differential diagnosis of hepatic disease occurring in patients receiving high dose salicylate therapy, regardless of serum salicylate levels.

Salicylates and renal function in rheumatoid arthritis.

The effect of salicylate treatment on the kidney, particularly medullary function, was investigated. In a retrospective analysis patients with rheumatoid arthritis (RA) treated with high doses of salicylates were shown to have inferior urinary concentrating power and increased excretion of N-acetyl-beta-D-glucosaminidase (NAG) when compared with patients who had not received salicylate treatment. A prospective study of renal funcition in healthy people and patients with RA starting salicylate in therapeutic doses showed that while epithelial cell excretion was only transiently raised in both groups the excretion of NAG was increased in all cases at three days and this increase was sustained at 10 days, all values being much higher in the patients than in the healthy subjects. Thus salicylate treatment does cause renal tubular damage but this damage results in only minimal impairment of function and does not constitute a reason for withholding salicylate treatment.

Aspirin hepatitis.

A 20-year-old woman with systemic lupus erythematosus developed hepatitis while on high-dose aspirin therapy. Liver function tests indicated moderately severe hepatocellular dysfunction, which cleared after discontinuing the therapy. Subsequent rechallenge with aspirin resulted in hepatitis, proved by clinical, biochemical, and histological findings. A review of the literature suggests that salicylate-induced hepatotoxicity occurs much more frequently than previously noted. An awareness of this potential complication is important when treating patients with high doses of salicylate.