Examination of pharmacokinetic variables in a cohort of patients with rheumatoid arthritis beginning therapy with methotrexate compared with a cohort receiving the drug for a mean of 81 months.

OBJECTIVE

To compare pharmacokinetic variables of a 7.5 mg dose of MTX in a cohort of patients with rheumatoid arthritis (RA) beginning therapy with the drug with a cohort of patients receiving the drug for a mean period of 81 months.

METHODS

Standard pharmacokinetic measures were performed in 35 patients beginning MTX therapy and 15 patients who had received the drug for a mean of 81 months.

RESULTS

No significant differences in area under the serum concentration versus time curve (AUC), maximal methotrexate concentration following dosing (Cmax), time to Cmax (Tmax), bioavailability (F), urinary MTX, renal clearance of MTX or creatinine clearance were observed between the 2 cohorts.

CONCLUSION

We were unable to demonstrate significant differences in pharmacokinetic variables in these cohorts with a 7.5 mg standard dose of MTX. It is possible that a difference may exist when a standard higher dose of MTX is compared in these types of patients.