Chlorambucil in Rheumatoid Arthritis

Systemic drug toxicity trends in immunosuppressive therapy of immune and inflammatory ocular disease

PURPOSE

To compare the relative toxicities of six systemic immunosuppressive drugs and systemic corticosteroids used to treat patients with severe ocular inflammatory disease and to identify factors influencing their occurrence.

METHODS

The authors reviewed the clinical records of 602 patients with ocular inflammatory disease treated with immunosuppressive drug therapy and/or systemic corticosteroids for adverse systemic effects while undergoing therapy. Proportional hazards regression analysis was performed to identify demographic and clinical factors that influence the occurrence of drug toxicity in these patients.

RESULTS

Immunosuppressive drug treatment was more likely to result in discontinuation of therapy because of toxic side effects than was corticosteroid treatment. However, unlike many of the side effects of corticosteroid treatment, the side effects of immunosuppressive therapy were reversible with reduction in dosage or discontinuation of the drug. Gastrointestinal symptoms and hematologic abnormalities accounted for the majority of reported side effects of the immunosuppressive medications. Neuro-psychiatric and endocrine side effects were common in patients taking prednisone. In 17 patients treated with prednisone, pathologic fractures developed, which involved the hips and the spine. Female sex and age older than 60 years also were identified as factors associated with intolerance to drug therapy in the authors' study population. Race and type of systemic ocular disease were not significant factors influencing tolerance to drug therapy.

CONCLUSION

These findings suggest that when properly administered and monitored for adverse effects, most immunosuppressive agents used in the current study have similar risk profiles with relatively few serious therapeutic mishaps and largely reversible side effects. In contrast, corticosteroids can result in permanent disabilities as a result of long-term treatment.

Treatment of antigen-induced arthritis in rabbits by the intra-articular injection of methylprednisolone, 90Y or chlorambucil

Rabbits with a bilateral antigen-induced arthritis were injected intra-articularly (i.a.) in one joint with methylprednisolone (1 mg), 90Y (18.5 MBq) or chlorambucil (1 mg) as a single dose. The severity of arthritis was determined by measuring joint swelling and skin surface temperature, macroscopic and histological changes in the joint being assessed 8 weeks after induction of arthritis when the rabbits were killed. Methylprednisolone injected at the time of antigen challenge or 3 weeks later caused a reduction in joint swelling and temperature (P < 0.05) for 1 to 6 weeks after injection. 90Y had an initial proinflammatory effect lasting several days, but later caused a modest reduction in joint swelling for up to 4 weeks (P < 0.05). Eight weeks after induction of arthritis, neither methylprednisolone nor 90Y-treated joints showed any significant reduction in erosion or histopathology compared with control arthritic joints. Chlorambucil injected 1 week after antigen challenge caused a rapid reduction in joint swelling which was maintained for the duration of the study. Joint surface temperature was reduced to a lesser extent. Eight weeks after induction of arthritis, chlorambucil-treated joints showed a decrease (P < 0.05) in all of the parameters of disease pathology assessed. Treatment with chlorambucil intra-articularly was clearly more effective than with methylprednisolone or 90Y at the doses employed and deserves further study as a potential treatment for chronic synovitis.

Pharmacokinetic basis for the comparative antitumour activity and toxicity of chlorambucil, phenylacetic acid mustard and beta, beta-difluorochlorambucil (CB 7103) in mice

This report describes the relationship between the pharmacokinetics, antitumour activity and toxicity of chlorambucil (CHL), phenylacetic acid mustard (PAAM) and beta, beta-difluorochlorambucil (beta-F2CHL) in mice. Pharmacokinetics were studied by HPLC, antitumour activity by a regrowth delay assay using the KHT murine sarcoma and toxicity by acute LD50. For both antitumour activity and acute toxicity the order of potency was: PAAM greater than CHL greater than beta-F2CHL. CHL and PAAM exhibited identical therapeutic indices, whereas that for beta-F2CHL was somewhat improved. CHL is metabolized by mitochondrial beta-oxidation to the 3,4-dehydro derivative (DeHCHL) and PAAM, and the latter is further metabolized to its monodechloroethylated derivative DeC-PAAM, presumably by hepatic microsomal enzymes. Administered PAAM gave only one metabolite, DeC-PAAM. Unexpectedly, despite beta, beta-disubstitution, beta-F2CHL was also beta-oxidized to give DeHCHL and PAAM, but at reduced rates. Further, metabolic switching was demonstrated with the appearance in large amount of 2 new, unidentified metabolites, which may be dechlorethylation products. The pharmacokinetics of administered CHL, PAAM and beta-F2CHL differ in that the plasma clearance was fastest for CHL, slowest for PAAM and intermediate for beta-F2CHL. For the metabolites, CHL produced peak plasma concentrations of DeHCHL and PAAM, respectively, 7-fold and 2-fold greater than those produced by beta-F2CHL. However, despite these differences, exposures to total bifunctional nitrogen mustards were similar following administration of the 3 drugs and therefore cannot account for their differential activity. In contrast, there was a good correlation between potency and PAAM exposure, which is highest after treatment with PAAM, intermediate after CHL and lowest after beta-F2CHL. In plasma, 3.2% of PAAM is present as nonprotein-bound free drug, compared to 1.3% for DeHCHL, 0.9% for CHL and 0.45% for beta-F2CHL. We propose the amount of free bifunctional nitrogen mustard, itself partly dependent on the extent of metabolism, to be of major importance for the in vivo potency of CHL analogues.

Therapeutic progress--review VI. Treatment of rheumatoid arthritis

Anti-rheumatic drugs used in rheumatoid arthritis fall into two distinct groups: non-steroidal anti-inflammatory and second-line drugs. Non-steroidal anti-inflammatory drugs give early symptomatic improvement and reduce the degree of acute inflammatory synovitis. Second-line drugs such as gold or D penicillamine exert an anti-inflammatory effect only after two to three months and act by suppressing disease activity: these reduce the ESR and other acute phase responses. However, the evidence that any of these drugs halt the progression of radiological changes or can be used as long-term agents to control the disease over a period of years is weak. The current use of anti-rheumatic drugs follows a general pattern with non-steroidal anti-inflammatory drugs used alone in patients with mild disease, whereas patients with severe disease also receive second-line drugs. As yet the long-term effect of this policy is not known. Cytotoxic drugs should be restricted to patients with severe disease who either fail to respond to conventional second-line drugs or have active extra-articular disease, particularly those with vasculitis.