Cardiovascular thromboembolic adverse effects associated with cyclooxygenase-2 selective inhibitors and nonselective antiinflammatory drugs.

BACKGROUND: Concerns of increased cardiovascular (CV) thromboembolic adverse effects from nonsteroidal antiinflammatory drugs (NSAIDs, both nonselective [NS]-NSAIDs and cyclooxygenase [COX]-2 selective inhibitors) have prevented their use despite numerous benefits. METHODS: In this descriptive review, we critically examine the randomized, active- and placebo-controlled studies, observational trials, and meta-analyses evaluating the CV adverse effects associated with long-term and short-term use of COX-2 selective inhibitors and NS-NSAIDs. The potential mechanisms for these CV effects are also presented. RESULTS: Although the studies evaluating the CV risks have limitations, there appears to be an increased CV risk with both COX-2 selective inhibitors and NS-NSAIDs, particularly in high-risk patients. Therefore, the United States Food and Drug Administration has given a similar "boxed" warning highlighting the potential for increased risk of CV events associated with their use. Nevertheless, there are differences in the CV risks between COX-2 selective inhibitors (e.g., higher CV risk with rofecoxib than celecoxib) as well as differences in the CV risks between individual NS-NSAIDs (e.g., higher CV risks with diclofenac than naproxen). CONCLUSIONS: Until long-term, prospective, randomized, adequately powered, clinical studies in relevant patient populations have been completed, the CV risks associated with the use of NSAIDs, especially in high-risk patients, will likely continue to be controversial. Nevertheless, the benefits of their short-term (e.g., perioperative) use in patients without CV risks probably outweigh their potential CV adverse effects. Finally, careful risk/benefit assessment should be undertaken and both COX-2 selective inhibitors and NS-NSAIDs should be used with caution in patients with CV risk factors.

Modulation of endothelial and smooth muscle function by bed rest and hypoenergetic, low-fat nutrition.

Prolonged microgravity alters the regulation of the peripheral vasculature. The influence of reduced food intake, as often observed in astronauts, on vascular function is unclear. In a randomized, four-phase, crossover study, the effect of simulated microgravity (13 days of bed rest), energetic restriction (-25%, fat reduced), and their combination on endothelium-dependent and -independent vasodilation was compared with ambulatory control conditions. Using venous occlusion plethysmography, cumulative intra-arterial dose-response curves to endothelium-dependent (acetylcholine) and -independent (sodium nitroprusside) vasodilators were constructed in 10 healthy male volunteers before and on day 13 of each of the four intervention periods. Bed rest combined with normoenergetic nutrition impaired the dose-response to acetylcholine (ANOVA, P = 0.004) but not to sodium nitroprusside, whereas hypoenergetic diet under ambulatory conditions improved responses to acetylcholine (P = 0.044) and sodium nitroprusside (P < 0.001). When bed rest was combined with hypoenergetic diet, acetylcholine responses did not change. Similarly, under control conditions, no change was observed. Individual changes in the total cholesterol-to-HDL ratio were correlated with changes in endothelial and vascular smooth muscle relaxation. In conclusion, short-term bed rest impairs endothelium-dependent arterial relaxation in humans. A hypoenergetic, low-fat diet modulates serum lipids, improves endothelium-dependent and -independent relaxation, and may antagonize the unfavorable effects of simulated microgravity on endothelial function.

Endothelial venodilator response in carriers of genetic polymorphisms involved in NO synthesis and degradation.

AIMS: Polymorphisms of the NOSIII gene and of the CYBA gene have been associated with a number of pathological conditions such as arterial hypertension, coronary artery disease, and myocardial infarction. Because endothelium-dependent vasodilation is impaired in these disorders, we hypothesized that polymorphisms of NOSIII or CYBA might modulate endothelial function of venous capacitance vessels already before cardiovascular disease becomes overt. METHODS: Endothelium-dependent and -independent venodilation was assessed by measuring local vascular responses to bradykinin and sodium nitroprusside in the dorsal hand vein after preconstriction with phenylephrine in 72 healthy male Caucasians after careful exclusion of cardiovascular risk factors. Genotyping was performed for polymorphisms of the NOSIII gene (T-786C, G894T, (CA)(n)) and the CYBA gene (C242T). RESULTS: Genotype distribution for each polymorphism followed the Hardy-Weinberg equilibrium. In all studied single nucleotide polymorphisms no significant difference between the respective genotypes and the venodilator response to either sodium nitroprusside or bradykinin was observed, and the number of CA repeat copies was not related to the venodilator response to bradykinin. Mean venodilation induced by bradykinin 50 ng min(-1) (+/-SEM) for homozygote carriers of the single nucleotide polymorphisms was 48.9 +/- 8.5% venodilation (G894T; wild type: 49.8 +/- 6.9), 50.3 +/- 11.0% venodilation (T-786C; wild type: 42.6 +/- 5.2), and 30.4 +/- 9.1% venodilation (C242T; wild type: 49.2 +/- 6.0), respectively. CONCLUSIONS: This study suggests that the studied polymorphisms of NOSIII and CYBA do not significantly modulate endothelium-dependent venodilation in individuals without vascular risk factors.

Rapid detection of polymorphisms of the nitric oxide cascade.

NOS3 (endothelial nitric oxide (NO) synthase) and p22phox (subunit of NAD(P)H oxidase) are two genes whose products are involved in formation and degradation of NO, a ubiquitous signaling molecule largely responsible for the maintenance of normal endothelial function. The G894T polymorphism of NOS3 and the C242T polymorphism of p22phox are reportedly associated with numerous cardiovascular diseases. For each polymorphism we developed a rapid and reliable method with the hybridization probes format on the LightCycler and compared it with conventional PCR-restriction fragment length polymorphism (PCR-RFLP) analysis with regard to reliability, duration and cost. The new methods are more reliable, faster and less expensive than PCR-RFLP analysis and therefore represent a significant advantage in the detection of two candidate risk factors for cardiovascular diseases.

Dose-dependent increase of saquinavir bioavailability by the pharmaceutic aid cremophor EL.

AIMS: Bioavailability of orally administered drugs depends on several factors including active excretion, e.g. by P-glycoprotein (PGP), and presystemic metabolism, e.g. by cytochrome P450 3A (CYP3A), in both gastrointestinal tract and liver. Many drugs including saquinavir are substrates of both PGP and CYP3A. It was the aim of this study to test whether the extremely low bioavailability of saquinavir can be increased dose-dependently in vivo by cremophor EL, an 'inactive' pharmaceutic aid known to inhibit PGP in vitro. METHODS: In a randomized, placebo-controlled, double-blind, four phase cross-over design single doses of oral saquinavir (Invirase, 600 mg, without food) were administered with increasing single doses of oral cremophor EL (up to 5000 mg) to eight healthy, male individuals. Saquinavir plasma concentrations were determined by LC/MS/MS up to 48 h after intake. Main outcome measures were area under the plasma concentration time curve (AUC), peak concentration (Cmax), time to reach Cmax (tmax) and terminal elimination half-life (t(1/2)). RESULTS: Cremophor EL dose-dependently increased Cmax, AUC(0,4 h), and AUC(0,infinity) of saquinavir. As compared with placebo, the increment observed after 5000 mg cremophor EL was 13-fold for both Cmax and AUC(0,4 h) and 5-fold for AUC(0,infinity). The terminal half-life and the time to reach Cmax (tmax) were unchanged. CONCLUSIONS: Cremophor EL increased the systemic availability of saquinavir without affecting its elimination suggesting that cremophor EL is not devoid of pharmacological action and acts as a modulator of the absorption process, probably by inhibiting intestinal PGP.