Diflunisal in rheumatoid arthritis

Influence of chronic diflunisal treatment on the plasma levels, metabolism and excretion of indomethacin

The single-dose pharmacokinetics of indomethacin following 100 mg rectally was measured in two groups of 8 healthy subjects before and after diflunisal 500 mg p.o. once daily, or 500 mg in the morning and 1000 mg in the evening, until steady state conditions were reached. A further group of 8 healthy subjects was given 50 mg indomethacin rectally before and after diflunisal 500 mg p.o. twice daily. High dose diflunisal (1500 mg/day) decreased the renal clearance of indomethacin from 21.9 to 1.8 ml/min (92%) and reduced the renal excretion of both unchanged (63%) and conjugated (82%) indomethacin. The apparent total body clearance (0.12 l/h/kg), apparent volume of distribution (0.98 l/kg), and volume of distribution at steady state (0.80 l/kg) were decreased by 47%, 35% and 30%. The maximum plasma concentration (2.4 micrograms/ml) and total area under the curve (13.0 micrograms x h/ml) were increased by 40% and 119%, respectively. The terminal elimination half-life (5.7 h) and mean residence time (6.7 h) were slightly prolonged (7.0 h and 8.8 h) in the presence of diflunisal. The contribution of metabolism to the overall elimination of indomethacin was increased by only 2%. Similar results were obtained when the subjects were challenged with the low dose of diflunisal (500 mg/day), although the magnitude of the changes were smaller. The interaction between indomethacin and diflunisal may be due to competition both at the metabolic (conjugation) and the excretory (tubular secretion) levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Cutaneous reactions to nonsteroidal anti-inflammatory drugs. A review

The nonsteroidal anti-inflammatory drugs are one of the most commonly prescribed classes of drugs used in medical practice. This review discusses the diverse cutaneous reactions associated with nonsteroidal anti-inflammatory drugs. Adverse cutaneous reactions occur most frequently with benoxaprofen, piroxicam, sulindac, meclofenamate sodium, zomepirac sodium, and phenylbutazone. The most serious adverse cutaneous reactions, Stevens-Johnson syndrome and toxic epidermal necrolysis, appear to be most often associated with sulindac and phenylbutazone. Tolmetin and zomepirac sodium, two structurally similar pyrrole derivatives, have been associated with a disproportionate number of cases of anaphylactoid reactions. Among the currently marketed nonsteroidal anti-inflammatory drugs, piroxicam appears to have the highest rate of phototoxic reactions. This phototoxic eruption is most often vesiculobullous.

Diflunisal 500-750 mg versus aspirin 2600-3900 mg in the treatment of rheumatoid arthritis

Diflunisal was compared to aspirin in a 12-week, double-blind, parallel, multicenter rheumatoid arthritis study. One hundred twenty-six (126) patients received diflunisal and 123 patients received aspirin. Both treatment groups demonstrated significant improvement from baseline in joint pain, morning stiffness, grip strength, walking time and painful and swollen joint scores. For these parameters, the only statistically significant difference between the groups was that diflunisal was more effective than aspirin for overall joint pain at week 2. The overall evaluation by patients and by investigators showed significantly better responses in those treated with diflunisal at weeks 1 and 12. Diflunisal produced significantly less gastrointestinal pain and tinnitus than aspirin. Neither drug showed unusual frequency of adverse effects as determined in the laboratory. Long-term studies using a higher-dose regimen are suggested to further define the efficacy and tolerability of diflunisal in the treatment of patients with rheumatoid arthritis.

The effect of diflunisal on hyaluronic acid production by 'activated' human synovial fibroblasts

1 Cultured human synovial fibroblasts were 'activated' by leucocytes or poly (I) . poly (C) to overproduce hyaluronic acid. 2 Diflunisal in concentrations of 30, 15 and 10 microgram/ml completely abrogated the overproduction of hyaluronic acid induced by leucocytes. 3 Diflunisal (10 microgram/ml), indomethacin (2 microgram/ml) and aspirin (200 microgram/ml) partially inhibited the overproduction of hyaluronic acid induced by poly (I) . poly (C), although none of them decreased it to control non 'activated' levels. 4 Diflunisal 25 microgram/ml completely abrogated hyaluronic acid overproduction induced by poly (I) . poly (C). 5 This model could be an in vitro indicator for in vivo pharmacological levels of anti-inflammatory drugs.