Pharmacokinetics of methotrexate administered by intramuscular and subcutaneous injections in patients with rheumatoid arthritis.

The serum concentrations and the pharmacokinetics of low-dose methotrexate (MTX) were compared after both intramuscular (IM) and subcutaneous (SQ) injections in 5 patients with rheumatoid arthritis. Values for the observed peak concentration, the time to the observed peak concentration, and the area under the time versus concentration curve for IM injections were not significantly different from these values for SQ injections. These results suggest that IM and SQ are interchangeable routes of administration. SQ administration may be a more convenient and less painful way of administering low-dose MTX.

Acute effects of steroids on immune complex profile of patients with systemic lupus erythematosus. Correlation of profile with development of target organ involvement.

Eleven patients with active systemic lupus erythematosus, previously untreated, were studied to 1) determine the acute effect of corticosteroids on circulating immune complex (CIC) levels and 2) correlate the initial CIC profile with the development of organ system involvement. Using serial measurements of CIC as detected by assays for cryoglobulins and binding to C1q, Raji cells, and rheumatoid factor, we found that levels of CIC change little during the first month of high dose daily steroid therapy, but they uniformly decrease to near normal by 6 to 12 months. High levels of CIC detected by Raji cell assay early in the course of systemic lupus erythematosus and before steroid therapy appear to be predictive of the development of chronic lupus nephritis (P less than 0.005).

Interaction between rheumatoid factor and antibody/DNA complexes: enhancement of complement fixation.

The influence of rheumatoid factor (RF) on the complement mediated binding of antibody/double-stranded DNA immune complexes to red blood cells has been investigated. Our results indicate that RF enhances this binding reaction, apparently by fixing complement via its own Fc region. These findings suggest that under certain circumstances, RF may play an exacerbating role in the antibody/DNA induced glomerulonephritis of systemic lupus erythematosus.

Renal vein thrombosis associated with nephrotic syndrome and gold therapy in rheumatoid arthritis.

In this case of renal vein thrombosis secondary to a nephrotic syndrome, we postulate renal disease resulted from gold therapy. We know of no previous report relating gold toxicity and renal vein thrombosis. It should be emphasized that with increasing use of gold, proteinuria and nephrotic syndrome may be more common than once suspected and, when present, predispose to the development of renal vein thrombosis.