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A study of the plasma levels of pentaerythritol mononitrate following administration of pentaerythritol tetranitrate in combination with meprobamate and diphenhydramine.

The systemic absorption of meprobamate, diphenhydramine and pentaerythritol tetranitrate (PETN) has been demonstrated following oral administration of a formulation containing all three drug substances to human volunteers. A study undertaken in dogs has also been made of the pharmacokinetics of the major nitrated metabolite of PETN when the parent drug is administered with and without meprobamate and diphenhydramine. Pentaerythritol mononitrate shows a six-fold increase in both peak plasma concentrations and area under the 0-12 hour plasma concentration-time curve when PETN is co-administered with a combination of meprobamate, diphenhydramine and nicotinic acid. No such increase is apparent when either meprobamate or diphenhydramine is excluded from the dose. Further increases in pentaerythritol mononitrate plasma levels and AUC 0-12 h are observed when all of the drugs are administered as the formulated coated tablet (VisanoCor).

Adult↗

Effects of nonintermittent treatment of rabbits with pentaerythritol tetranitrate on vascular reactivity and superoxide production.

Pentaerythritol tetranitrate is an organic nitrate ester that undergoes metabolization to pentaerythritol, pentaerythritol trinitrate, pentaerythritol dinitrate and pentaerythritol mononitrate. Recent data suggested that pentaerythritol tetranitrate is endowed with vasoprotective activities in experimental atherosclerosis. This study was undertaken to gain insight into the underlying mechanism. The basic mechanism of action of all pentaerythritol nitrates was evaluated by measuring liberation of nitric oxide (NO), stimulation of human soluble guanylate cyclase and vasorelaxation in rabbit aorta. A subsequent in vivo study in New Zealand White rabbits was performed to investigate the effects of a 4 months lasting nonintermittent oral treatment with 6 mg pentaerythritol tetranitrate kg(-1) day(-1) on vascular superoxide production, endothelium dependent vasorelaxation and vasorelaxation to pentaerythritol tetranitrate itself. The formation rates of NO from the pentaerythritol nitrates (100 microM, n = 5) in presence of 5 mM cystein were (in nM min(-1)): 62.1 +/- 3.2 (pentaerythritol tetranitrate), 21.3 +/- 0.9 (pentaerythritol trinitrate), 6.4 +/- 0.6 (pentaerythritol dinitrate) and 3.2 +/- 0.4 (pentaerythritol mononitrate). Similarly, the pD2 values (-log M) for half-maximal activation of soluble guanylate cyclase decreased from pentaerythritol tetranitrate (3.391 +/- 0.09, n = 4) to pentaerythritol mononitrate (2.655 +/- 0.04, n = 3) as did the pD2 values (in -log M) for half-maximal relaxation of rabbit aortic rings (n = 7) from pentaerythritol tetranitrate (8.3 +/- 0.17) to pentaerythritol mononitrate (5.0 +/- 0.11). Significant correlations were found between the NO formation rates and the pD2 values for enzyme stimulation (r = 0.98, P = 0.002) and vasorelaxation (r = 0.90, P = 0.049) suggesting that these effects of the pentaerythritol nitrates were mediated by NO. The results of the in vivo study showed that aging induces a significant increase of aortic superoxide production (median values, n = 10) from 2.45 nM mg(-1) min(-1) (age 7 months) to 3.39 nM mg(-1) min(-1) (age 11 months, P < 0.01) that was prevented by concurrent treatment with pentaerythritol tetranitrate (2.76 nM mg(-1) min(-1)). In vitro vasorelaxation to pentaerythritol tetranitrate was identical in all groups indicating absence of nitrate tolerance. Endothelium-dependent vasorelaxation was also identical in all groups. These data suggest that oral treatment with pentaerythritol tetranitrate reduces vascular oxidant stress by an NO-dependent pathway, which may contribute to the vasoprotective activity of pentaerythritol tetranitrate in experimental atherosclerosis.

Administration, Oral↗

Pentaerythritol propoxylate: a new crystallization agent and cryoprotectant induces crystal growth of 2-methylcitrate dehydratase.

In the search for macromolecular crystallization conditions, the precipitant is probably the most important variable, such that when problematic crystals are encountered there is always the question of whether an alternative precipitant might resolve the problem. During an effort to obtain high-quality crystals of several problematic proteins, two new agents, pentaerythritol propoxylate and pentaerythritol ethoxylate, yielded well ordered quality crystals where more traditional precipitants were unsuccessful. Pentaerythritol propoxylate and pentaerythritol ethoxylate contain a pentaerythritol backbone to which organic polymers are bound, forming a branched polymer. As such, they are larger than small organic precipitants such as low molecular-weight alcohols or 2-methyl-2,4-pentanediol, but behave differently to polyethylene glycols. These compounds have been used to crystallize an enzyme encoded by the Salmonella enterica prpD gene that catalyzes the dehydration of 2-methylcitrate to form 2-methyl-cis-aconitate. While the PrpD protein has crystallized readily under a number of conditions, the resultant crystals were unsuitable for a crystal structure determination. The new crystals obtained with 25-40% pentaerythritol propoxylate belong to the orthorhombic space group C222(1), with unit-cell parameters a = 73.2, b = 216.4, c = 214.3 A, and diffract beyond 2.0 A with synchrotron radiation. A further benefit of this precipitant for crystallization is its ability to function as a cryoprotectant, allowing the crystals to be transferred directly from the mother liquor to the nitrogen stream at 113 K.

Aconitate Hydratase↗

[Twenty-eight-day repeated dose toxicity test of pentaerythritol in F344 rats].

A twenty-eight-day repeated dose toxicity test of pentaerythritol at dose levels of 1000 or 0 mg/kg/day was carried out in male and female F344 rats. Thirteen animals of each sex were divided into 2 groups with 7 rats receiving pentaerythritol treatment and 6 rats served saline as control. All groups received an i.g. administration daily for 28 days. As to serum biochemical and hematological examinations, there were no serious differences between the pentaerythritol-treated rats and the control rats. On histopathological examination, no specific changes were observed in the pentaerythritol-treated rats. Based on these results, the no-observed-effect level of pentaerythritol can be concluded to be more than 1000 mg/kg/day.

Administration, Oral↗

Oxidative stress and mitochondrial aldehyde dehydrogenase activity: a comparison of pentaerythritol tetranitrate with other organic nitrates.

Mitochondrial aldehyde dehydrogenase (ALDH-2) was recently identified to be essential for the bioactivation of glyceryl trinitrate (GTN). Here we assessed whether other organic nitrates are bioactivated by a similar mechanism. The ALDH-2 inhibitor benomyl reduced the vasodilator potency, but not the efficacy, of GTN, pentaerythritol tetranitrate (PETN), and pentaerythritol trinitrate in phenylephrine-constricted rat aorta, whereas vasodilator responses to isosorbide dinitrate, isosorbide-5-mononitrate, pentaerythritol dinitrate, pentaerythritol mononitrate, and the endothelium-dependent vasodilator acetylcholine were not affected. Likewise, benomyl decreased GTN- and PETN-elicited phosphorylation of the cGMP-activated protein kinase substrate vasodilator-stimulated phosphoprotein (VASP) but not that elicited by other nitrates. The vasodilator potency of organic nitrates correlated with their potency to inhibit ALDH-2 dehydrogenase activity in mitochondria from rat heart and increase mitochondrial superoxide formation, as detected by chemiluminescence. In contrast, mitochondrial ALDH-2 esterase activity was not affected by PETN and its metabolites, whereas it was inhibited by benomyl, GTN applied in vitro and in vivo, and some sulfhydryl oxidants. The bioactivation-related metabolism of GTN to glyceryl-1,2-dinitrate by isolated RAW macrophages was reduced by the ALDH-2 inhibitors benomyl and daidzin, as well as by GTN at concentrations >1 microM. We conclude that mitochondrial ALDH-2, specifically its esterase activity, is required for the bioactivation of the organic nitrates with high vasodilator potency, such as GTN and PETN, but not for the less potent nitrates. It is interesting that ALDH-2 esterase activity was inhibited by GTN only, not by the other nitrates tested. This difference might explain why GTN elicits mitochondrial superoxide formation and nitrate tolerance with the highest potency.

Aldehyde Dehydrogenase↗

Blood levels of the metabolites of glyceryl trinitrate and pentaerythritol tetranitrate after administration of a two-step preparation.

Blood levels and urinary excretion rates of glyceryl trinitrate- pentaerythritol tetranitrate, and their less nitrate containing metabolites have been determined in ten human volunteers after a single dose of a two- step preparation containing glyceryl trinitrate and pentaerythritol tetranitrate. Blood levels accounted for peak levels of about 40% of the glyceryl trinitrate and 0.4% of the pentaerythritol tetranitrate metabolites, respectively. Within the first 24 h post administration 22% of the glyceryl trinitrate and 19% of the pentaerythritol tetranitrate were excreted as nitrate metabolites, chiefly in form of conjugates. The determinations were obtained by gas chromatography on extremely inactive columns and electron capture detection by means of derivatives.

Adult↗

The effect of high-dose pentaerythritol tetranitrate on the development of nitrate tolerance in rabbits.

Experimental studies with therapeutic doses of pentaerythritol tetranitrate (PETN) have shown unexpected actions such as a lack of nitrate tolerance and vasoprotective effects in atherosclerosis. We investigated the effect of a 3-week treatment with low- (6 mg kg(-1) day(-1), n=10) and high-dose (100 mg kg(-1) day(-1), n=10) oral PETN given twice daily on the development of nitrate tolerance in rabbits. We measured aortic relaxation in response to acetylcholine, S-nitroso-N-acetyl-D,L-penicillamine and PETN, constriction in response to phenylephrine and production of reactive oxygen species (ROS). Mean aortic pressure (AOPmean) and heart rate were measured after a single oral dose of PETN (50 mg kg(-1), n=6) and after increasing doses of pentaerythritol dinitrate (PEDN, n=5) and pentaerythritol mononitrate (PEMN, n=5) in anaesthetized rabbits. Oral PETN, even at high dosage, was not associated with nitrate tolerance. None of the aortic ring studies showed a difference in the responses to the vasodilators, while the vasoconstriction to phenylephrine was slightly reduced in both PETN groups. The production of vascular ROS was also not different. Oral PETN reduced AOPmean transiently (-19.3+/-4.4%, P<0.01 vs. controls) and i.v. administration of both PEMN and PEDN reduced AOPmean dose dependently (P<0.05, ANOVA). These results suggest that oral PETN elicits minor nitrate tolerance. This unique feature might be due to the slow onset of vasodilator activity of the predominantly active metabolites PEDN and PEMN and might contribute to the vasoprotective activity of PETN in atherosclerosis.

Animals↗

Degradation of pentaerythritol tetranitrate by Enterobacter cloacae PB2.

A mixed microbial culture capable of metabolizing the explosive pentaerythritol tetranitrate (PETN) was obtained from soil enrichments under aerobic and nitrogen-limiting conditions. A strain of Enterobacter cloacae, designated PB2, was isolated from this culture and was found to use PETN as a sole source of nitrogen for growth. Growth yields suggested that 2 to 3 mol of nitrogen was utilized per mol of PETN. The metabolites pentaerythritol dinitrate, 3-hydroxy-2,2-bis-[(nitrooxy)methyl]propanal, and 2,2-bis-[(nitrooxy)methyl]-propanedial were identified by mass spectrometry and 1H-nuclear magnetic resonance. An NADPH-dependent PETN reductase was isolated from cell extracts and shown to liberate nitrite from PETN, producing pentaerythritol tri- and dinitrates which were identified by mass spectrometry. PETN reductase was purified to apparent homogeneity by ion-exchange and affinity chromatography. The purified enzyme was found to be a monomeric flavoprotein with a M(r) of approximately 40,000, binding flavin mononucleotide noncovalently.

Aerobiosis↗

Synthesis of 3'-3'-linked oligonucleotides branched by a pentaerythritol linker and the thermal stabilities of the triplexes with single-stranded DNA or RNA.

Synthesis of 3'-3'-linked oligonucleotides branched by a pentaerythritol linker is described. The branched oligonucleotides were synthesized on a DNA/RNA synthesizer using a controlled pore glass (CPG) with a pentaerythritol linker carrying 4,4'-dimethoxytrityl (DMTr) and levulinyl (Lev) groups. The stability of the triplexes between the branched oligonucleotides and the target single-stranded DNA or RNA was studied by thermal denaturation. The oligonucleotides with the pentaerythritol linker formed thermally stable triplexes with the single-stranded DNA and RNA. Furthermore, the branched oligonucleotides containing 2'-O-methylribonucleosides, especially the oligonucleotide composed of 2'-deoxyribonucleosides and 2'-O-methylribonucleosides, stabilized the triplexes with the single-stranded DNA or RNA. Thus, the branched oligonucleotide containing 2'-O-methylribonucleosides may be a candidate for a novel antisense molecule by the triplex formation.

DNA↗

The behavior of pentaerythritol tetranicotinate in rat gastrointestinal tract as a prodrug.

The gas chromatographic assay method for pentaerythritol tetranicotinate, a nicotinic acid prodrug, and its hydrolysates was developed. The behavior of the drug in gastrointestinal tract was investigated in rat by using the method. The disappearance and hydrolysis of the drug were not observed in the gastric loop until 30 min. The rate of disappearance from the intestinal loop was 36.7% at 30 min which was significantly smaller than that of nicotinic acid. Little hydrolysis of the drug was observed in the buffer solution, pH 7.4, at 37 degrees up to 2 hr. However, the consecutive hydrolysis was observed when the drug was incubated with everted intestine or plasma. As to the rate of hydrolysis of the drug and its esterform hydrolysates by scraped intestinal mucosa, the ester to which the larger number of nicotinic acid was bound was hydrolyzed more rapidly. These results indicate that the orally administered drug is enzymatically hydrolyzed in the intestinal mucosa by a consecutive reaction. Although the hydrolysis rate of pentaerythritol tetranicotinate is rapid, the rate of its ester-form hydrolysate becomes slower gradually as the nicotinic acid is released. The released nicotinic acid is rapidly absorbed. The behavior of the drug revealed in this study suggests that pentaerythritol tetranicotinate is useful as a prodrug of nicotinic acid.

Animals↗

[Analysis for monobromo- and dibromo-pentaerythritol by gas chromatography].

A method for separation and determination of dibromo-pentaerythritol (DBPT), monobromo-pentaerythritol (MBPT), and tribromo-pentaerythritol (TBPT) by gas chromatography was developed. The conditions for determination were: BPX-70 capillary column, operated at 240 degrees C, with both FID detector and injector at 280 degrees C. Xylitol was the internal standard. Linear regression equations were YDBPT = 0.0423X-0.0124 (r = 0.9998) and YMBPT = 0.0634X-0.0835(r = 0.9966). This method is rapid, simple and accurate.

English Abstract↗

Validation of high-performance liquid chromatographic methods for analysis of sustained-release preparations containing nitroglycerin, isosorbide dinitrate, or pentaerythritol tetranitrate.

The assay of sustained-release tablets or capsules containing nitroglycerin, isosorbide dinitrate, or pentaerythritol tetranitrate by high-performance liquid chromatography is described. Acetonitrile was found to be the sample preparation solvent with the most general applicability to these products. Anisole was used as an internal standard for nitroglycerin and pentaerythritol tetranitrate, while 4-chloroacetanilide was used for isosorbide dinitrate. The method, which uses a C18 bonded-phase column, a methanol-water mobile phase, and 214-nm detection, was shown to be accurate, linear, and reproducible.

Acetonitriles↗

Differential effects of pentaerythritol tetranitrate and nitroglycerin on the development of tolerance and evidence of lipid peroxidation: a human in vivo study.

OBJECTIVES: We investigated the development of nitrate tolerance after continuous exposure to nitroglycerin (GTN) as compared with pentaerythritol tetranitrate (PETN) in humans. BACKGROUND: Sustained therapy with GTN causes tolerance and has been associated with increased production of free oxygen radicals by the endothelium. Pentaerythritol tetranitrate is an organic nitrate that has been used in the therapy of angina. There have been no investigations concerning the development of tolerance to PETN in humans. Animal investigations suggested that continuous therapy with PETN does not cause increased free radical production or hemodynamic tolerance. METHODS: We randomized 30 healthy volunteers to continuous GTN (0.6 mg/h/24 h), long-acting PETN (60 mg orally three times a day) or no treatment (control group) for seven days. We studied systemic blood pressure responses and venous volume responses to GTN with strain-gauge plethysmography. The levels of cytotoxic aldehydes and isoprostanes were measured as markers of free radical-mediated lipid peroxidation. RESULTS: Tolerance, as demonstrated by blood pressure and forearm plethysmography, developed in the GTN group and was absent in the PETN group (p < 0.05). Therapy with GTN was associated with a significant increase in plasma markers of lipid peroxidation. This response was not observed in those treated with PETN (isoprostanes: control: 38 +/- 5; GTN: 59 +/- 6; PETN: 38 +/- 3 microg/ml; p < 0.005). CONCLUSIONS: Treatment with PETN does not cause tolerance and is not associated with evidence of increased free radical production.

Administration, Cutaneous↗

Spectrophotometric determination of pentaerythritol tetranitrate in tablets.

A sensitive spectrophotometric method is reported for the quantitative determination of pentaerythritol tetranitrate in tablets. The method is based on reduction of pentaerythritol tetranitrate with zinc and calcium chloride, and reaction of the nitroso compound thus formed with 1-naphthylamine in acidic medium. The reaction gives a purple product having an absorbance maximum at 545 nm. Beer's law is obeyed in the concentration range of 1-10 micrograms/mL of reaction mixture. The presence of meprobamate in tablets does not interfere with the proposed analytical determination.

Calcium Chloride↗