Effects of angiotensin II blockade on inflammation-induced alterations of pharmacokinetics and pharmacodynamics of calcium channel blockers.

BACKGROUND AND PURPOSE: Inflammation elevates plasma verapamil concentrations but diminishes pharmacological response. Angiotensin II is a pro-inflammatory mediator. We examined the effect of angiotensin II receptor blockade on the pharmacokinetics and pharmacodynamics of verapamil, as well as the binding properties and amounts of its target protein in calcium channels, in a rat model of inflammation. EXPERIMENTAL APPROACH: We used 4 groups of male Sprague-Dawley rats (220-280 g): inflamed-placebo, inflamed-treated, control-placebo and control-treated. Inflammation as pre-adjuvant arthritis was induced by injecting Mycobacterium butyricum on day 0. From day 6 to 12, 30 mg kg(-1) oral valsartan or placebo was administered twice daily. On day 12, a single oral dose of 25 mg kg(-1) verapamil was administered and prolongation of the PR interval measured and plasma samples collected for verapamil and nor-verapamil analysis. The amounts of the target protein Ca(v)1.2 subunit of L-type calcium channels in heart was measured by Western blotting and ligand binding with (3)H-nitrendipine. KEY RESULTS: Inflammation reduced effects of verapamil, although plasma drug concentrations were increased. This was associated with a reduction in ligand binding capacity and amount of the calcium channel target protein in heart extracts. Valsartan significantly reversed the down-regulating effect of inflammation on verapamil's effects on the PR interval, and the lower level of protein binding and the decreased target protein. CONCLUSIONS AND IMPLICATIONS: Reduced responses to calcium channel blockers in inflammatory conditions appeared to be due to a reduced amount of target protein that was reversed by the angiotensin II antagonist, valsartan.

Drug-disease interactions: reduced beta-adrenergic and potassium channel antagonist activities of sotalol in the presence of acute and chronic inflammatory conditions in the rat.

Inflammation may influence response to pharmacotherapy. We investigated the effect of inflammation on response to sotalol, a beta-adrenergic receptor and potassium channel antagonist. Racemic sotalol (40 mg kg(-1)) was administered to healthy, acutely (interferonalpha 2a-induced) and chronically (Mycobacterium butyricum-induced adjuvant arthritis) inflamed male Sprague-Dawley rats (n=4 - 6/group). Another group of interferon-treated rats received 3 mg kg(-1) of anti-TNF antibody infliximab. Electrocardiogram (ECG) recorded and plasma sotalol concentration monitored for 6 h. The study was repeated in acutely inflamed rats following administration of stereochemically pure individual sotalol enantiomers [40 mg kg(-1) S (potassium channel blocker) or 20 mg kg(-1) R (beta-adrenergic/potassium channel blocker)]. Chronic arthritis was readily evident. Acute arthritis was associated with elevated segmented neutrophils and increased plasma nitrite and tumour necrosis factor (TNF) concentrations. Sotalol affected ECG in all rats. In both inflamed groups, however, response to sotalol in prolongation of QT interval (potassium channel sensitivity) was reduced. The effect of PR interval (beta-adrenergic activity) was also reduced following administration of the racemate and R-enantiomer. No significant differences in pharmacokinetics were observed between control and inflamed rats. Infliximab reduced nitrite and TNF concentrations and reversed the effect of acute inflammation on both PR and QT intervals. The reduced electrocardiographic responses to sotalol is likely due to the influence of inflammation on the action of the drug on both beta-adrenergic and potassium channel receptors secondary to over-expression of pro-inflammatory cytokines and/or nitric oxide. Our observation may have therapeutic consequences in all conditions where inflammatory mediators are increased.

Pharmacological protection of NSAID-induced intestinal permeability in the rat: effect of tempo and metronidazole as potential free radical scavengers.

Recently, NSAID-induced changes in both the structure and function of the distal intestine have been found to occur more frequently and with greater toxicological significance than previously thought. We have previously validated a suitable animal model to evaluate intestinal permeability changes using orally administered 51Cr-EDTA that correlates with intestinal ulceration. In this study we investigated the suitability of metronidazole and the nitroxide stable free radical scavenger (tempo) as protective agents against NSAID-induced intestinal permeability. Male Sprague-Dawley rats were dosed with two doses of metronidazole (50 mg/kg, 12 and 1 h pre-NSAID) or a single 100 mg/kg dose of tempo 1 h prior to NSAIDs. The urinary excretion of the orally administered marker 51Cr-EDTA was measured. Both tempo and metronidazole dramatically reduced indomethacin (20 mg/kg) and flurbiprofen (10 mg/kg)-induced intestinal permeability. All the animals exposed to indomethacin alone died within 48-96 h and presented with histological evidence of drug-induced enteropathy, ulceration and frank peritonitis. Protection by tempo and metronidazole suggests that free radicals and/or bacteria may be important mediators in the pathogenesis of intestinal mucosal damage induced by NSAIDs. Nitric oxide donor compounds used concomitantly with NSAIDs may protect gastrointestinal tract.

Stereoselective disposition of etodolac enantiomers in synovial fluid.

The synovial fluid (SF) uptake of the chiral nonsteroidal anti-inflammatory drug, etodolac, was studied in six arthritic patients, 2 hours (n = 1) or 12 hours (n = 5) after a single 200 mg dose of racemate. Marked stereoselectivity was seen in both SF and plasma; concentrations of pharmacologically inactive R-etodolac were up to 10-fold greater than active S-etodolac. Concentrations of S-etodolac were greater in SF than in plasma (SF:plasma ratio = 1.98 +/- 0.8): No such difference was seen for R-etodolac (SF:plasma = 0.91 +/- 0.3). Considerable concentrations of conjugated enantiomers were present in SF. In vitro equilibrium dialysis studies in drug-spiked samples showed that the unbound fraction of both enantiomers in SF was greater than in plasma; both fluids bound R more extensively than S etodolac. Therapeutically active S-etodolac has greater concentrations in synovial fluid than plasma during the post-distributive phase, which may be of possible clinical relevance.

Pharmacokinetics of ketoprofen enantiomers in young and elderly arthritic patients following single and multiple doses.

Ketoprofen (KT), a chiral nonsteroidal anti-inflammatory drug (NSAID), is marketed and used as a racemic mixture. In healthy volunteers, negligible differences have been reported between the plasma time courses of KT enantiomers. Using a stereospecific high-performance liquid chromatographic (HPLC) assay measuring (R)- and (S)-KT in plasma and urine, pharmacokinetics of the enantiomers following single (50 mg) and then multiple (50 mg every 6 h for 3 d) doses were delineated in nine young and nine elderly arthritic patients. There were no significant differences between pharmacokinetic indices calculated after single and multiple doses, or between the two groups. In plasma, there were no significant differences between intact enantiomers in either patient group. However, significantly more conjugated (S)-KT was found in elderly patient plasma. Similar to findings in healthy volunteers, elimination of conjugated KT in both patient groups was more extensive for the (S)-, as compared with the (R)-isomer. It is suggested that age-dependent impaired elimination of conjugated (S)-KT, along with preferential biliary excretion of conjugated (R)-KT, is responsible for these observations.

Low-dose methotrexate kinetics in arthritis.

Twelve patients with either rheumatoid or psoriatic arthritis were injected with a 10-mg bolus dose of methotrexate (MTX) either intramuscularly (n = 6) or intravenously (n = 6) and the MTX concentration in their sera was determined by radioimmunoassay. MTX concentration--time data fitted triexponential equations. Doses injected intramuscularly were rapidly and completely absorbed. There were no significant intergroup differences in drug mean t 1/2, volume of distribution, and total body clearance. In nine patients serum MTX concentrations remained above the suggested critical level of 0.01 mumol throughout the 24-hr study irrespective of the route of administration, but MTX did not cumulate in the serum. We conclude that the behavior of low doses of MTX in patients with arthritis closely resembles the pattern in patients receiving intermediate and high doses for the treatment of neoplasia.

Clinical significance of total serum IgE determination in screening of Iranian Russian thistle pollen hypersensitive individuals.

Total serum IgE concentrations of normal and Russian thistle (Salsola pestifer) pollen hypersensitive individuals were determined in an Iranian population, using the solid phase radioimmunoassay technique. The mean values were 963.7 and 885.3 ng/ml, respectively, which are much higher than normal values given for non-Iranian populations. In addition, no significant differences were found between observed values (P = 0.1) for normal and allergic individuals. The effect of common parasitic infestation in the Iranian population in causing high serum IgE levels is discussed.