A method of evaluation of the influence of aspirin formulations on gastrointestinal microbleeding in humans

Review: acute human models of gastric mucosal injury

The use of acute human models of gastric mucosal injury has been stimulated by a need to understand more fully the problems of non-steroidal anti-inflammatory drugs but such models have other applications. None is ideal and they all share certain drawbacks. For none of them has a precise relationship to clinical events been established and they have all tended to be employed on a population of young healthy subjects who are not those at greatest clinical risk. Of individual methods mucosal potential difference is an indirect measure which is too often affected by other influences to be acceptable as a measure of mucosal injury when used alone, although it has some value as an adjunct to other measurements. Assay of DNA in gastric washings is a suitable technique for quantifying desquamation of gastric epithelial cells occurring in response to acute injury; on present evidence its significance is much more difficult to assess in the context of continuing challenge over several days. By contrast, measurement of microbleeding is more suitable for quantifying injury over several days of NSAID ingestion; little bleeding is recorded with a single acute challenge. Endoscopy can demonstrate macroscopic lesions which result from mucosal injury--injury which is quantified more easily and sensitively by measurements of cellular exfoliation or bleeding. Paradoxically, endoscopy's strength has been to underline the scientific weakness of acute models because it shows that it is rare for ulcers, which are the lesions of clinical concern to develop in these studies.

Fecal blood loss and plasma salicylate study of salicylsalicylic acid and aspirin

Using a placebo-controlled methodology, 20 healthy volunteers housed in a clinical research facility for 23 days were studied for fecal blood loss and plasma salicylate levels after taking salsalate (salicylsalicylic acid) or aspirin. Daily dosages were 3000 mg salsalate or 3900 mg aspirin. Aspirin produced statistically significant gastrointestinal blood loss over control levels and over that produced by salsalate (P less than 0.01). Blood loss with salsalate was not different than that with placebo. Despite the intentional disparity of dosages between the two drugs, plasma salicylate levels were not statistically different. Side effects occurred at about equal frequency with either drug. Most prominent were headache and nausea. However, concomitant upper respiratory infection in 12 subjects rendered interpretation difficult.

Gastrointestinal blood loss caused by controlled-release and conventional acetylsalicylic acid tablets

Gastrointestinal blood loss has been studied following oral administration of the novel controlled-release acetylsalicylic acid tablet preparation Acetard and the instant-release acetylsalicylic acid tablet Magnecyl (Ph. Nord. 63). Acetard contains micro-encapsulated acetylsalicylic acid crystals having an in vitro release time of approximately 4 hours. The investigation was carried out as a two-part, randomized cross-over trial, and with a test dosage of either 1 g X 4 or 2 g X 2 per day, given to 10 and 14 male students, respectively, during two 5-day periods separated by a one week interval. The dosage of the plain formulation was maintained at 1 g X 4 daily in both parts of the investigation. Faeces were collected every 24 hours throughout the trial, covering a total of 4 weeks. Blood loss was measured using the 51Cr labelling technique. Acetard was found to cause statistically significantly less gastrointestinal blood loss as compared with the plain formulation, irrespective of whether Acetard was given twice or four times a day.

Gastro-intestinal blood loss during administration of indoprofen, aspirin and ibuprofen

The acute effect of three non-steroidal anti-inflammatory drugs, ibuprofen, acetylsalicylic acid (ASA) and indoprofen, on faecal blood loss was investigated in 15 subjects by means of 51Cr-labelled erythrocytes. Ibuprofen (900 mg/day for 5 days) and indoprofen capsules and tablets (300 mg and 600 mg/day for 5 days, respectively) slightly increased the amount of blood eliminated in faeces. The increase was of the same order of magnitude for both doses of indoprofen. ASA (1,500 mg/day for 5 days) caused about a 6-fold increase in blood loss. Four days after withdrawal of ASA, faecal blood was still about twice as high as in faeces of subjects given ibuprofen and indoprofen. The method appears sensitive and reliable for comparison of the immediate effect of anti-inflammatory drugs on gastro-intestinal mucosa.

Physical form as a determinant of effect of buffered acetylsalicylate formulations on gi microbleeding

During a 48-day period, 12 male dogs received four buffered sodium acetylsalicylate formulations, quantitatively virtually identical (a homogenenous disintegrating swallow tablet, a swallow tablet in which the sodium acetylsalicylate was contained in a dissolving core, an encapsulated powder, and an aqueous suspension), at 650-mg aspirin equivalent doses twice daily during four 7-day treatment periods (each preceded by a 5-day period of no treatment) in a complete changeover fashion. Mean daily fecal blood losses of 0.75, 1.37, 1.43, and 2.89 ml were observed in the 12 dogs during treatment with the aqueous suspension, the homogeneous tablet, the encapsulated powder, and the core tablet, respectively. These findings indicate that the physical form of buffered acetylsalicylate formulations is a critical factor in the effect of such formulations on GI microbleeding.

Effect of naproxen on gastrointestinal microbleeding following acetylsalicylate medication

This study was undertaken to determine if substitution of naproxen for ASA does influence salicylate-induced gastrointestinal bleeding. Twelve normal volunteers were selected and given increasing doses of salicylate until guaiac tests were consistently positive. Autologous labeling of their red blood cells with 51-Cr was used to quantitate the microbleeding. After two weeks on ASA, six subjects were double blindly switched to naproxen and six to placebo for another two weeks of observation. Two-way analysis of variance on the raw data shows a significant treatment effect associated with a significant interaction in both groups. Final analysis on a logarithmic scale permits orthogonal contrasts to be accurately made without any significant remaining interaction. It is concluded that substitution of naproxen for ASA at a dose of 500 mg daily is accompanied by a rapid reduction of microbleeding to "normal" levels.