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Terkeltaub R.A.,San Diego Medical Center | Furst D.E.,University of California at Los Angeles | Digiacinto J.L.,Salamandra LLC | Kook K.A.,Salamandra LLC | Davis M.W.,URL Pharma
Arthritis and Rheumatism | Year: 2011

Objective Drug-drug interactions can limit the safety of colchicine for treating rheumatic diseases. Seven separate drug-drug interaction (DDI) studies were performed to elucidate the in vivo effects of concomitant treatment with colchicine and known inhibitors of cytochrome P450 3A4 (CYP3A4)/P-glycoprotein (cyclosporine, ketoconazole, ritonavir, clarithromycin, azithromycin, verapamil ER [extended release]), and diltiazem ER) on the pharmacokinetics of colchicine. The objective was to develop colchicine-dosing algorithms with improved safety. Methods All studies were open-label, non-randomized, single-center, one-sequence, two-period DDI experiments, using two 0.6-mg doses of colchicine, separated by a minimum 14-day washout period, followed by administration of the approved on-label regimen of known CYP3A4/P-glycoprotein inhibitors. Plasma concentrations of colchicine, but not the reference CYP3A4/P-glycoprotein inhibitors, were determined, and the pharmacokinetic parameters were calculated. Results The ratios of the maximum concentration and area under the curve from time 0 to infinity for colchicine plus CYP3A4/P-glycoprotein inhibitors versus colchicine alone were >125% across all studies, with the exception of studies involving azithromycin. Significant DDIs were present when single doses of colchicine were coadministered with most of the selected CYP3A4/P-glycoprotein inhibitors. Recommended colchicine dose reductions of 33-66% for the treatment of acute gout and 50-75% for prophylaxis were calculated for concomitant therapy with each agent, with the exception of no dose adjustment when colchicine is used in combination with azithromycin. Conclusion These studies provide quantitative evidence regarding drug interactions and necessary adjustments in the dose of colchicine if colchicine treatment is continued during therapy with multiple CYP3A4/P-glycoprotein inhibitors. We demonstrated the need for specific reductions in the dose of colchicine when it is used in combination with 2 broadly prescribed calcium channel blockers (verapamil ER and diltiazem ER) and that the dose of colchicine does not need to be adjusted when it is used in combination with azithromycin. Copyright © 2011 by the American College of Rheumatology.

Davis M.W.,Takeda Pharmaceutical | Wason S.,Takeda Pharmaceutical | DiGiacinto J.L.,Salamandra LLC
Consultant Pharmacist | Year: 2013

Objective: Review the magnitude and clinical relevance of drug-drug interactions between a new formulation of colchicine, used to treat gout, and antibiotics. Setting and Practice Description: Relevant to community and institutional pharmacists servicing patients with gout. Practice Innovation: Pharmacists have clear roles for the identification of drug-drug interactions, providing recommendations for alternative therapy or dose adjustments/ modifications, and monitoring for interactionrelated adverse events. Main Outcome Measures: Colchicine is metabolized via cytochrome P450 3A4 (CYP3A4); therefore, coadministration with agents that inhibit this isoenzyme can produce elevated colchicine plasma concentrations, resulting in severe and sometimes fatal adverse events. Knowledge of the potential for drug-drug interactions involving antibiotics (e.g., macrolide antibiotics, azole antifungals) allows pharmacists to help patients avoid serious adverse events. Results: Pharmacokinetic studies have demonstrated that the maximum plasma concentration (Cmax) and drug exposure (as assessed by area under the plasma concentration time curve [AUC]) of colchicine are increased by 277% and 282%, respectively, after coadministration with clarithromycin. Similarly, coadministration with ketoconazole increases colchicine Cmax and AUC by 102% and 212%, respectively. Other antibiotics that are strong CYP3A4 inhibitors include itraconazole and telithromycin, whereas erythromycin and fluconazole are moderate inhibitors of the isoenzyme CYP3A4. Coadministration of CYP3A4 inhibitors (particularly clarithromycin) and colchicine has resulted in acute colchicine toxicity manifested by severe gastrointestional toxicity, bone marrow suppression, multiorgan failure, and death. Conclusion: Pharmacist awareness of potentially clinically significant interactions between colchicine and antibiotics that inhibit CYP3A4 can help to ensure the efficacy of colchicine is realized while mitigating serious toxicities and minimizing the risk of adverse events.

Godfrey A.R.,PRACS Institute Ltd. | DiGiacinto J.,Salamandra LLC | Davis M.W.,Mutual Pharmaceutical Company
Clinical Therapeutics | Year: 2011

Background: Fenofibrate is used to treat primary hypercholesterolemia, mixed lipidemia, and hypertriglyceridemia in adults who do not respond to nonpharmacologic measures. Fenofibrate is a prodrug that is rapidly and completely hydrolyzed to fenofibric acid, the active moiety. A new orally administered agent, fenofibric acid, was developed as an alternative to fenofibrate. Objective: Two separate studies were conducted to evaluate the bioequivalence of fenofibric acid relative to fenofibrate under fasted and fed (standard breakfast) conditions, characterize the pharmacokinetic profile, and assess the safety and tolerability of fenofibric acid. Methods: In study 1 (fasted), during each study period, volunteers received a single 105-mg dose of fenofibric acid or single 145-mg dose of fenofibrate (depending on their randomization scheme) after an overnight fast (a minimum fast of 10 hours). A 7-day washout period followed the first treatment period, after which the volunteers received the alternate treatment. Study 2 followed a similar dosing scheme and differed only in that volunteers received their single dose after being fed a standard meal (575 calories, of which 36% were contributed by fat). Serial blood samples in both studies were collected up to 72 hours after drug administration. The pharmacokinetic parameters of interest for assessing bioequivalence were AUC 0-t, AUC 0-∞, C max, and T max. The criterion for a lack of difference between products was a 90% CI between 0.80 and 1.25 for the fenofibric acid:fenofibrate ratios for AUC 0-t, AUC 0-∞, and C max. Tolerability was assessed by adverse events (AEs), laboratory parameters, vital signs, and physical examinations. Results: Volunteers in study 1 (fasted; n = 54) were aged 18 to 43 years; 19 (35%) were men and 35 (65%) were women; mean weight was 155.2 pounds (range, 103.0-267.0 pounds); and 48 (89%) were white, 1 (2%) was black, and 5 (9%) were white/American Indian/Alaskan native/Asian. Volunteers in study 2 (fed; n = 54) were aged 18 to 43 years; 27 (50%) were men and 27 (50%) were women; mean weight was 161.9 pounds (range, 112.0-225.0 pounds); and 51 (94%) were white (including 2 Hispanic) and 3 (6%) were black. The 90% CIs about the ratio of the fenofibric acid geometric mean to the fenofibrate geometric mean were within the 80% and 125% limits for the pharmacokinetic parameters C max, AUC 0-t, and AUC 0-∞ of the ln-transformed data in both study 1 (fasted) and study 2. In study 1 (fasted), 14 volunteers (26%) experienced a total of 29 AEs; the most common nonlaboratory AEs were dizziness (6%) and headache (4%). In study 2, 12 volunteers (22%) experienced a total of 19 AEs; the most common nonlaboratory AEs were headache (17%) and dry throat (4%). AEs were generally mild or moderate in intensity. Conclusions: In these 2 single-dose studies, these healthy volunteers administered a single oral dose of 105-mg fenofibric acid met the US Food and Drug Administration regulatory criteria for assuming bioequivalence to a single oral dose of 145-mg fenofibrate tablets with respect to the rate and extent of fenofibric acid absorption in both fed and fasted states. Fenofibric acid at the dose studied was well tolerated in this population. ClinicalTrials.gov identifiers: NCT00961116 and NCT00960687. © 2011 Elsevier HS Journals, Inc.

Baddeley T.C.,University of Aberdeen | McCaffrey J.,Salamandra LLC | Storey J.M.D.,University of Aberdeen | Cheung J.K.S.,University of Aberdeen | And 5 more authors.
Journal of Pharmacology and Experimental Therapeutics | Year: 2015

Methylthioninium (MT) is a tau aggregation inhibitor with therapeutic potential in Alzheimer's disease (AD). MT exists in equilibrium between reduced [leucomethylthioninium (LMT)] and oxidized (MT+) forms; as a chloride salt [methylthioniniumchloride (MTC), "methylene blue"], it is stabilized in its MT+ form. Although the results of a phase 2 study of MTC in 321 mild/moderate AD subjects identified a 138-mg MT/day dose as the minimum effective dose on cognitive and imaging end points, further clinical development of MT was delayed pending resolution of the unexpected lack of efficacy of the 228-mg MT/day dose. We hypothesized that the failure of dose response may depend on differences known at the time in dissolution in simulated gastric and intestinal fluids of the 100-mg MTC capsules used to deliver the 228-mg dose and reflect previously unsuspected differences in redox processing of MT at different levels in the gut. The synthesis of a novel chemical entity, LMTX (providing LMT in a stable anhydrous crystalline form), has enabled a systematic comparison of the pharmacokinetic properties of MTC and LMTX in preclinical and clinical studies. The quantity of MT released in water or gastric fluid within 60 minutes proved in retrospect to be an important determinant of clinical efficacy. A further factor was a dose-dependent limitation in the ability to absorb MT in the presence of food when delivered in the MT+ form as MTC. A model is presented to account for the complexity of MT absorption, which may have relevance for other similar redox molecules. Copyright © 2014 by The American Society for Pharmacology and Experimental Therapeutics

Wason S.,URL Pharma Inc. | Digiacinto J.L.,Salamandra LLC | Davis M.W.,URL Pharma Inc.
Postgraduate Medicine | Year: 2012

Objective: Colchicine and cyclosporine are often administered together, particularly in patients who have undergone solid-organ transplantation. However, the potential for drug-drug interactions between these agents resulting in colchicine toxicity is high. Methods: This study sought to determine the effect of cyclosporine (100-mg capsule) on the pharmacokinetics of the US Food and Drug Administration-approved formulation of colchicine (0.6-mg tablet) after single oral-dose administration in 24 healthy subjects under fasted conditions in a phase 1, single-sequence, 2-period drug-drug interaction trial. Results: Coadministration of cyclosporine increased colchicine maximum observed plasma concentration, area under the plasma concentration-time curve to the last measurable time point, and area under the plasma concentration-time curve to time infinity on average by 224%, 216%, and 215% (ie, almost doubled), respectively, and decreased colchicine oral clearance on average by 72% (from 48.24 to 13.42 L/h), indicating substantially higher colchicine exposures when combined with cyclosporine, compared with colchicine alone. Conclusion: The dose of colchicine should be reduced by $ 50% when colchicine and cyclosporine are administered concurrently for treatment and prophylaxis of gout fares or treatment of patients with familial Mediterranean fever. Health care professionals should be vigilant for potential adverse events during colchicine/cyclosporine coadministration, notably in patients who have undergone solid-organ transplantation. © Postgraduate Medicine.

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