Clearance of indomethacin occurs predominantly by renal glucuronidation

Herb-drug interaction in the protective effect of Alpinia officinarum against gastric injury induced by indomethacin based on pharmacokinetic, tissue distribution and excretion studies in rats

Alpinia officinarum Hance of the Chinese traditional herb for the treatment of emesis, abdominal pain and diarrhea has been used to counteract gastric disease induced by indomethacin in rats without obvious side effects. However, the role of herb-drug interaction between indomethacin and A. officinarum based on pharmacokinetic, tissue distribution and excretion still remains unknown. In this study, an ultra-fast liquid-tandem mass spectrometry (UFLC-MS/MS) method was developed for simultaneous determination of indomethacin and its three metabolites, O-desmethylindomethacin (ODI), deschlorobenzoylindomethacin (NDI) and indomethacin acyl-β-D-glucuronide (IDAβG) by oral administration of indomethacin solution with and without the ethanolic extract of A. officinarum and applied to comparative pharmacokinetic, tissue distribution and excretion studies. Our results clarified that oral administration of A. officinarum produced significant alterations in the pharmacokinetic parameters of indomethacin. And the pharmacokinetic interaction between indomethacin and A. officinarum reduced the systemic exposure of indomethacin and increased its elimination. Tissue distribution results demonstrated that co-administration of A. Officinarum could not reduce the accumulation of indomethacin in the target tissue of the stomach, but could accelerate the excretions of indomethacin and its three metabolites including ODI, NDI and IDAβG in the bile and feces of rats in the excretion study. Therefore, A. Officinarum might have a gastrointestinal protective effect through the interaction role with indomethacin based on the pharmacokinetics and excretion in rats.

Effect of indomethacin on bile acid-phospholipid interactions: implication for small intestinal injury induced by nonsteroidal anti-inflammatory drugs

The injurious effect of nonsteroidal anti-inflammatory drugs (NSAIDs) in the small intestine was not appreciated until the widespread use of capsule endoscopy. Animal studies found that NSAID-induced small intestinal injury depends on the ability of these drugs to be secreted into the bile. Because the individual toxicity of amphiphilic bile acids and NSAIDs directly correlates with their interactions with phospholipid membranes, we propose that the presence of both NSAIDs and bile acids alters their individual physicochemical properties and enhances the disruptive effect on cell membranes and overall cytotoxicity. We utilized in vitro gastric AGS and intestinal IEC-6 cells and found that combinations of bile acid, deoxycholic acid (DC), taurodeoxycholic acid, glycodeoxycholic acid, and the NSAID indomethacin (Indo) significantly increased cell plasma membrane permeability and became more cytotoxic than these agents alone. We confirmed this finding by measuring liposome permeability and intramembrane packing in synthetic model membranes exposed to DC, Indo, or combinations of both agents. By measuring physicochemical parameters, such as fluorescence resonance energy transfer and membrane surface charge, we found that Indo associated with phosphatidylcholine and promoted the molecular aggregation of DC and potential formation of larger and isolated bile acid complexes within either biomembranes or bile acid-lipid mixed micelles, which leads to membrane disruption. In this study, we demonstrated increased cytotoxicity of combinations of bile acid and NSAID and provided a molecular mechanism for the observed toxicity. This mechanism potentially contributes to the NSAID-induced injury in the small bowel.

Probenecid inhibits the glucuronidation of indomethacin and O-desmethylindomethacin in humans. A pilot experiment

Indomethacin is metabolized in humans by O-demethylation, and by acyl glucuronidation to the 1-O-glucuronide. Indomethacin, its metabolite, and their conjugates can be measured directly by gradient high-pressure liquid chromatographic analysis without enzymic deglucuronidation. The pharmacokinetic profile of indomethacin and some preliminary pharmacokinetic parameters of indomethacin obtained from one human volunteer are given. In plasma only the parent drug indomethacin is present, while in urine the acyl and ether glucuronides are present in high concentrations. This confirms other reports that indomethacin and O-desmethylindomethacin may be glucuronidated in the kidney. Probenecid is a known substrate for renal glucuronidation. If indomethacin is glucuronidated in the human kidney like probenecid, then this glucuronidation might be reduced or inhibited under probenecid co-medication. This pilot experiment shows that probenecid reduced the acyl glucuronidation of indomethacin by 50% and completely inhibited the formation of O-desmethylindomethacin acyl and ether glucuronide.

Low molecular weight proteins as carriers for renal drug targeting: naproxen coupled to lysozyme via the spacer L-lactic acid

Low molecular weight proteins (LMWPs) are potential carriers for targeting drugs to the kidney. To test whether ester bonds are suitable for the reversible drug conjugation, the antiinflammatory drug naproxen (Nap) was conjugated to the LMWP lysozyme (LYSO) via an ester bond using an L-lactic acid spacer (Nap-lact-LYSO, 1:1:1). The distribution and degradation of the conjugate in rats were compared to those of an equimolar mixture of free drug and LMWP and of a directly coupled conjugate without spacer (Nap-LYSO). The plasma clearance of Nap-lact-LYSO closely resembled that of Nap-LYSO and LYSO itself. Its major accumulation site appeared to be the kidney as demonstrated by extracorporal gamma-camera counting of the LMWP. Renally released naproxen was excreted in the urine as 6-desmethyl-naproxen-sulfate (6-DMN-S). Apparently the kidneys represent the main sites of demethylation and sulfation after administration of the LMWP-coupled drug. In addition, the renal excretion of naproxen (including its metabolites) was significantly delayed and sustained as compared to that after injection of uncoupled naproxen. Using the L-lactic acid spacer LMWP conjugation, the renal selectivity of Nap was increased 5.6 +/- 0.41-fold. Additional in vitro studies with Nap-lact-LYSO revealed that renal generation of the parent drug coincided with formation of low molecular weight catabolites, mainly as naproxen-L-lactic acid-lysine (Nap-lact-Lys). This indicated that in vitro the rate of cleavage of the ester bond is significantly slower than digestion of the carrier backbone itself.(ABSTRACT TRUNCATED AT 250 WORDS)