Chloroquine + Methotrexate = Precautionary

Effect on Concentration

Chloroquine
Unknown
Applies within class?
No
Methotrexate
Decrease
Applies within class?
No

Pharmacologic Effects

Chloroquine
Effect
N/A
Applies within class?
No
Methotrexate
Effect
N/A
Applies within class?
No

Interaction History

N/A

Last Updated 19-May-2020

Summary

Chloroquine significantly reduced methotrexate exposures. The clinical significance of this is indeterminate.

Sources

Chloroquine Reduces the Bioavailability of Methotrexate in Patients With Rheumatoid Arthritis. A Possible Mechanism of Reduced Hepatotoxicity ^

Study Design

Eleven patients (ages 41-75 years) who were taking oral doses of MTX (15 mg/week) were studied after a dose of MTX alone and after a dose of MTX plus CQ (250 mg). Plasma and urine samples were collected for 24 hours after dose intake, and the concentrations of MTX and its major metabolite 7-hydroxymethotrexate were determined by high-performance liquid chromatography.

Study Results

Administration of CQ together with MTX caused a reduction in the area under the plasma MTX concentration versus time curve (AUC). The median value of individual AUC ratios (MTX/MTX CQ) was 1.6 (95 confidence interval 1.2-3.6).

Study Conclusions

The most likely mechanism for the interaction is that CQ reduces the bioavailability of MTX. This gives a possible explanation for a suggested reduction in MTX-associated liver toxicity by coadministration of CQ. The significance of the interaction for the therapeutic effect remains to be elucidated.

References

Seideman P. Chloroquine reduces the bioavailability of methotrexate in patients with rheumatoid arthritis. a possible mechanism of reduced hepatotoxicity. Arthritis Rheum. ; 6: 830-3.