Reduced Heart Exposure of Diclofenac by Its Polymeric Micellar Formulation Normalizes CYP-Mediated Metabolism of Arachidonic Acid Imbalance in An Adjuvant Arthritis Rat Model: Implications in Reduced Cardiovascular Side Effects of Diclofenac by Nanodrug Delivery.

In this study, we tested whether the extent of drug presence in the heart contributes to the elevated cardiovascular risk of nonsteroidal anti-inflammatory drugs (NSAIDs). A fluorescently tagged nanoformulation of an NSAID with high cardiovascular (CV) risk (diclofenac) was developed as diclofenac ethyl ester (DFEE) encapsulated in traceable (cyanine-5.5-labeled) polymeric micelles (DFEE-TM) based on methoxypoly(ethylene oxide)-block-poly(ε-caprolactone)(PEO-b-PCL) (MW, 5000:3500 g/mol). Diclofenac pharmacokinetics and tissue distribution, as well as ex vivo near-infrared images of organs and whole bodies, were compared between healthy rats and rats with adjuvant arthritis (AA) following the administration of a single intravenous (iv) dose of DFEE-TM. Moreover, the biodistribution and antiarthritic activity of DFEE-TM were compared with those of free diclofenac (once-daily intraperitoneal, ip, 10 mg/kg for 7 days). The concentration ratios of cytochrome-P450-mediated cardiotoxic (20-hydroxyeicosatetraenoic acid) over cardioprotective (epoxyeicosatrienoic acids) metabolites of arachidonic acid (ArA) in the heart, kidneys, and plasma were measured as markers of cardiotoxicity. The nanocarrier was found in the joints of AA, but not in those of healthy rats. Both free diclofenac and DFEE-TM comparably controlled AA. Diclofenac delivery via PEO-b-PCL micelles reduced the accumulation of diclofenac in the heart of AA rats. Despite similar antiarthritic activity, the polymeric micellar formulation showed a reduction in the ratio of cardiotoxic-over-cardioprotective eicosanoids of ArA in the heart and plasma of AA rats. The results showed the positive effect of diclofenac prodrug nanodelivery in changing the normal biodistribution of diclofenac away from the heart, leading to lowered diclofenac-induced biomarkers of cardiotoxicity in the heart and plasma of AA rats.

Dose-dependency of the cardiovascular risks of non-steroidal anti-inflammatory drugs.

Non-steroidal anti-inflammatory drugs (NSAIDs) are commonly used to treat pain and inflammatory conditions such as arthritis. However, both arthritis and many NSAIDs increase cardiovascular (CV) risks. The dose-dependency of the elevated CV risks of NSAIDs has not been well-studied. We tested the hypothesis that low but still effective doses of these drugs are void of CV side effects. As the model drug, we chose diclofenac because of its known high CV toxicity, as markers of CV risks, we assessed concentrations of cytochrome P450-mediated metabolites of arachidonic acid (ArA), and we used adjuvant arthritis as an experimental model of arthritis. Following 7 daily doses (2.5-15 mg/kg), the effective dosage range of diclofenac was identified (> 5 mg/kg/day). While 7 consecutive days of low therapeutic doses did not alter the CYP-mediated ArA metabolism, the highest dose of 15 mg/kg/day caused imbalances in ArA metabolic profiles toward cardiotoxicity by increasing the ratio of cardiotoxic 20-hydroxyeicosatetraenoic acid over cardioprotective epoxyeicosatrienoic acids. This is suggestive of dose-dependency of NSAID cardiotoxicity, and that low therapeutic doses may be void of CV side effects. Human studies are needed to examine the safety of low but effective doses of NSAIDs.

Delivery and Biodistribution of Traceable Polymeric Micellar Diclofenac in the Rat.

The nonsteroidal anti-inflammatory drugs elevate cardiovascular risk, perhaps, due to their accumulation in the heart and kidneys. We designed nanodelivery systems for cardiotoxic diclofenac to reduce its presence in these organs. Diclofenac ethyl ester (DFEE) was encapsulated in traceable micelles based on poly(ethylene oxide)-b-poly(ε-caprolactone) (DFEE-PCL-TM) or poly(ethylene oxide)-b-poly(α-benzyl carboxylate-ε-caprolactone) (DFEE-PBCL-TM). Diclofenac pharmacokinetics and tissue distribution were studied after intravenous (iv) and intraperitoneal administration of the nanoformulations and compared with those after iv doses of free diclofenac (n = 3-6/group). The average diameters for DFEE-PBCL-TM and DFEE-PCL-TM were 37.2 ± 0.06 and 45.1 ± 0.06 nm, respectively. Drug concentration dropped below the assay sensitivity after free drug administration in 6 h, but persisted for 24 h following DFEE-PBCL-TM (2.3 ± 1.4 µg/mL) and DFEE-PCL-TM (1.9 ± 0.6 µg/mL) iv administration. The diclofenac heart:blood and kidney:blood ratios were 5- to 12-fold lower with the nanoformulations than with free diclofenac. Near-infrared fluorescence measurements in tissues suggested exposure patterns to nanocarriers parallel with those achieved for delivered diclofenac by nanoformulations. Administration of DFEE-PCL-TM by iv or intraperitoneal injection, resulted in comparable pharmacokinetics and 6 h postdose near-infrared fluorescence in the heart, kidneys, liver, and spleen. When compared to each other, DFEE-PBCL-TM showed significantly lower diclofenac levels in the heart compared to DFEE-PCL-TM (0.3 ± 0.03 vs. 0.5 ± 0.1 µg/g). Developed nanoformulations of diclofenac prolonged diclofenac circulation and reduced its presence in the heart and kidneys, strongly suggesting cardiac-safe delivery vehicles for diclofenac.