Newly-Published Colchicine Safety Data Provide First Evidence-Based Dosing Guidance to Avoid Potentially Serious Interactions With Commonly Prescribed Drugs

PHILADELPHIA, Aug. 11, 2011 /PRNewswire/ — Newly-published
results from a series of colchicine safety studies provide
physicians with the first evidence-based dosing guidance for
colchicine when co-administered with certain commonly prescribed
drugs, helping doctors and patients avoid serious and potentially
life-threatening drug-drug interactions.

The study results, published in a paper titled “Evidence Basis
of a Novel Colchicine Dose Reduction Algorithm to Predict and
Prevent Colchicine Toxicity in the Presence of P-gp/CYP450 3A4
Inhibitors,” appear in the August issue of Arthritis &
Rheumatism, the journal of the American College of
Rheumatology. The paper recommends colchicine dose reductions when
used with medications such as immunosuppressants, antibiotics,
hypertension drugs, anti-fungals and protease inhibitors.

The seven studies highlighted in the paper formed part of the
basis for URL Pharma’s New Drug Application (NDA) for Colcrys®
(colchicine, USP). Colcrys is the only single-ingredient colchicine
product to be reviewed and approved by the U.S. Food and Drug
Administration, and is indicated for the prophylaxis and treatment
of gout flares, and for the treatment of Familial Mediterranean
Fever (FMF).

The studies assessed cyclosporine, an immunosuppressant;
clarithromycin and azithromycin, two antibiotics; diltiazem and
verapamil, two hypertension drugs; ketoconazole, an anti-fungal
drug; and ritonavir, a protease inhibitor. Each of these drugs is
known to inhibit cytochrome P450 3A4 (CYP3A4) and/or P-glycoprotein
(P-gp).

Each of these drugs, except for azithromycin, was found to
interact significantly with standard colchicine dosing regimens, in
some cases more than doubling levels of colchicine in the blood and
increasing the risk of serious toxicities. Cyclosporine and
clarithromycin in particular increased peak colchicine blood levels
by nearly 300 percent. The authors recommended that colchicine
doses

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