Clinical pharmacokinetics and pharmacodynamics of glyceryl trinitrate and its metabolites

Effectiveness of a Glyceryl Trinitrate (GTN) Patch in Preventing Amputation, Improving Pain Control and Reducing the Size of Tissue Loss for a Patient With Critical Limb-Threatening Ischaemia (CLTI)

Background  Foot ulcer is a common complication of poorly controlled diabetes and peripheral vascular disease (PVD). The current standard of treatment for diabetic foot ulcers includes the management of underlying risk factors, wound debridement, use of antibiotics for infection, off-loading with cast, and revascularisation surgery. The glyceryl trinitrate (GTN) patch is currently off-licence in treating PVD or diabetic foot ulcers. This study aims to evaluate the effectiveness of the GTN patch in preventing amputation, improving pain control, and reducing the size of tissue loss (ulcer/gangrene) or localised ischaemic area. Method This is a pilot study of 30 patients who were started on the GTN patch from February 2020 to October 2021. Inclusion criteria were patients who have critical limb-threatening ischaemia (CLTI) and with no viable options or are at high risk for revascularisation, both endovascular and open surgery. Patients who were on a GTN patch for less than six weeks at the time of data collection or had unclear outcomes were excluded. The outcomes were retrospectively collected on prevention of amputation, improvement in pain control, and reduction in tissue loss (the size of ulcer/gangrene) or localised ischaemic area with the use of a GTN patch. The binomial test was used to compare the observed outcome of the GTN patch and the expected outcome, which was assumed to be 50% in this study. Results  Ninety-three per cent (93%) of the patients who had GTN patches successfully avoided amputation (p<0.0001). Eighty-four per cent (84%) of patients reported better pain control (p=0.0022) and improvement in the size of ulcer/gangrene/localised ischaemic areas (p=0.0005). Conclusion The GTN patch is effective in preventing amputation, improving pain control, and reducing the size of ulcer/gangrene/localised ischaemic areas in patients who have end-stage CLTI and no viable options or who are at high risk for revascularisation surgery.

Nitroglycerin: a comprehensive review in cancer therapy

Nitroglycerin (NTG) is a prodrug that has long been used in clinical practice for the treatment of angina pectoris. The biotransformation of NTG and subsequent release of nitric oxide (NO) is responsible for its vasodilatating property. Because of the remarkable ambivalence of NO in cancer disease, either protumorigenic or antitumorigenic (partly dependent on low or high concentrations), harnessing the therapeutic potential of NTG has gain interest to improve standard therapies in oncology. Cancer therapeutic resistance remains the greatest challenge to overcome in order to improve the management of cancer patients. As a NO releasing agent, NTG has been the subject of several preclinical and clinical studies used in combinatorial anticancer therapy. Here, we provide an overview of the use of NTG in cancer therapy in order to foresee new potential therapeutic avenues.

Topical nitroglycerin to detect reversible microcirculatory dysfunction in patients with circulatory shock after cardiovascular surgery: an observational study

Persistent abnormalities in microcirculatory function are associated with poor clinical outcomes in patients with circulatory shock. We sought to identify patients with acutely reversible microcirculatory dysfunction using a low-dose topical nitroglycerin solution and handheld videomicroscopy during circulatory shock after cardiac surgery. Forty subjects were enrolled for the study, including 20 preoperative control and 20 post-operative patients with shock. To test whether microcirculatory dysfunction is acutely reversible during shock, the sublingual microcirculation was imaged with incident dark field microscopy before and after the application of 0.1 mL of a 1% nitroglycerin solution (1 mg/mL). Compared to the control group, patients with shock had a higher microcirculation heterogeneity index (MHI 0.33 vs. 0.12, p < 0.001) and a lower microvascular flow index (MFI 2.57 vs. 2.91, p < 0.001), total vessel density (TVD 22.47 vs. 25.90 mm/mm2, p = 0.005), proportion of perfused vessels (PPV 90.76 vs. 95.89%, p < 0.001) and perfused vessel density (PVD 20.44 vs. 24.81 mm/mm2, p < 0.001). After the nitroglycerin challenge, patients with shock had an increase in MFI (2.57 vs. 2.97, p < 0.001), TVD (22.47 vs. 27.51 mm/mm2, p < 0.009), PPV (90.76 vs. 95.91%, p < 0.001), PVD (20.44 vs. 26.41 mm/mm2, p < 0.001), venular RBC velocity (402.2 vs. 693.9 µm/s, p < 0.0004), and a decrease in MHI (0.33 vs. 0.04, p < 0.001. Thirteen of 20 patients showed a pharmacodynamic response, defined as an increase in PVD > 1.8 SD from shock baseline. Hemodynamics and vasoactive doses did not change during the 30-min study period. Our findings suggest a topical nitroglycerin challenge with handheld videomicroscopy can safely assess for localized recruitment of the microcirculatory blood flow in patients with circulatory shock and may be a useful test to identify nitroglycerin responsiveness.

Factors influencing the safety of outpatient coronary CT angiography: a clinical registry study

OBJECTIVES

Since the safety of coronary CT angiography (CTA) is of great importance, especially with regard to widening indications and increasing morbidity, the aim of this study was to assess influencing factors.

METHODS

Patients undergoing coronary CTA in a third-generation dual-source CT in a radiological centre were included in a clinical registry. Up to 20 mg metoprolol was administered intravenously to attain a heart rate ≤65/min. Glyceryl trinitrate (GTN) was administered in doses of 0.8 mg and 0.4 mg. Blood pressure was measured before the administration and after the CTA.

RESULTS

Out of 5500 consecutive patients (3194 men, 62.3 (54.9-70.0) years), adverse events occurred in 68 patients (1.2%) with mild anaphylactoid reactions (0.4%), vasovagal symptoms (0.3%) and extravasation (0.3%) being most frequent. Anti-allergic drugs were given in 17 patients, atropine in 3 patients and volume in 1 patient. Drug administration resulted in a significant mean arterial pressure decline (96.0 (88.3-106.0) vs 108.7 (99.7-117.3) mmHg; p<0.001). Patients who suffered systolic blood pressure drops >20 mmHg or >40 mmHg were older (66.5 (58.6-73.3) vs 60.5 (53.6-68.3) years; 70.2 (63.3-76.5) vs 62.1 (54.7-69.6) years), more often male (65.1% vs 54.4%; 68.9% vs 57.3%) and had higher Agatston score equivalents (83.0 (2.0-432.0) vs 15.0 (0.0-172.0); 163.0 (16.3-830.8) vs 25.0 (0.0-220.0); all p<0.001). GTN dose reduction lowered the fraction of patients suffering from blood pressure drops >20 mmHg or >40 mmHg from 34.5% to 27.4% and from 6.1% to 3.5% (both p<0.001), respectively. The proportion of coronary segments with impaired image quality did not differ significantly.

CONCLUSIONS

Coronary CTA with intravenous beta-blocker administration is a safe procedure in an outpatient setting as adverse events are rare and mostly mild. Reduced GTN doses can further improve safety by lowering the rate of significant blood pressure drops, which occurred especially in elderly men with increased plaque burden.

TRIAL REGISTRATION NUMBER

NCT03815123.

Therapeutic role of nitroglycerin against copper-nitrilotriacetate induced hepatic and renal damage

Earlier we have shown that exposure to copper-nitrilotriacetate (Cu-NTA) manifests toxicity by generating oxidative stress and potent induction of proliferative reaction in the liver and kidney. In the study, we look at the impact of nitroglycerin (GTN) administration on Cu-NTA-induced oxidative stress and hyperproliferative response in the liver and kidney. GTN administration intraperitoneally to male Wistar rats after Cu-NTA administration intraperitoneally caused substantial protection against Cu-NTA-induced tissue injury, oxidative stress and hyperproliferative response. Cu-NTA administration at a dose of 4.5 mg/kg body weight produces significant ( p < .001) elevation in biochemical parameters including aspartate aminotransferase (AST), alanine aminotransferase (ALT), blood urea nitrogen (BUN) and creatinine (CREA) with a concomitant increase in microsomal lipid peroxidation. Along with these alterations, we discovered a substantial increment in [3H]thymidine incorporation into hepatic and renal DNA synthesis ( p < .001). Cu-NTA-induced tissue damage and lipid peroxidation in hepatic and renal tissues were inhibited by GTN treatment in a dose-dependent manner ( p < .05–0.001). Furthermore, GTN can suppress the hyperproliferative response elicited by Cu-NTA by down-regulating the rate of [3H]thymidine incorporation into hepatic and renal DNA ( p < .01–0.001). Protective effect of GTN against Cu-NTA was also confirmed by histopathological changes in liver and kidney. This result suggests that GTN may serve as a scavenger for reactive oxygen species (ROS) and reduces toxic metabolites of Cu-NTA, thereby avoiding tissue injury and oxidative stress. Further, administration of NO inhibitor, NG-Nitroarginine methyl ester (L-NAME), exacerbated Cu-NTA induced oxidative tissue damage and cell proliferation. Overall, GTN reduces Cu-NTA-induced tissue damage, oxidative stress, and proliferative response in the rat liver and kidney, according to these findings. On the basis of the above results, present study suggests that GTN may be a potential therapeutic agent for restoration of oxidative damage and proliferation to liver and kidney.

Glyceryl Trinitrate: History, Mystery, and Alcohol Intolerance

Glyceryl trinitrate (GTN) is one of the earliest known treatments for angina with a fascinating history that bridges three centuries. However, despite its central role in the nitric oxide (NO) story as a NO-donating compound, establishing the precise mechanism of how GTN exerts its medicinal benefit has proven to be far more difficult. This review brings together the explosive and vasodilatory nature of this three-carbon molecule while providing an update on the likely in vivo pathways through which GTN, and the rest of the organic nitrate family, release NO, nitrite, or a combination of both, while also trying to explain nitrate tolerance. Over the last 20 years the alcohol detoxification enzyme, aldehyde dehydrogenase (ALDH), has undoubtedly emerged as the front runner to explaining GTN's bioactivation. This is best illustrated by reduced GTN efficacy in subjects carrying the single point mutation (Glu504Lys) in ALDH, which is also responsible for alcohol intolerance, as characterized by flushing. While these findings are significant for anyone following the GTN story, they appear particularly relevant for healthcare professionals, and especially so, if administering GTN to patients as an emergency treatment. In short, although the GTN puzzle has not been fully solved, clinical study data continue to cement the importance of ALDH, as uncovered in 2002, as a key GTN activator.

Nitric Oxide as a Central Molecule in Hypertension: Focus on the Vasorelaxant Activity of New Nitric Oxide Donors

Cardiovascular diseases include all types of disorders related to the heart or blood vessels. High blood pressure is an important risk factor for cardiac complications and pathological disorders. An increase in circulating angiotensin-II is a potent stimulus for the expression of reactive oxygen species and pro-inflammatory cytokines that activate oxidative stress, perpetuating a deleterious effect in hypertension. Studies demonstrate the capacity of NO to prevent platelet or leukocyte activation and adhesion and inhibition of proliferation, as well as to modulate inflammatory or anti-inflammatory reactions and migration of vascular smooth muscle cells. However, in conditions of low availability of NO, such as during hypertension, these processes are impaired. Currently, there is great interest in the development of compounds capable of releasing NO in a modulated and stable way. Accordingly, compounds containing metal ions coupled to NO are being investigated and are widely recognized as having great relevance in the treatment of different diseases. Therefore, the exogenous administration of NO is an attractive and pharmacological alternative in the study and treatment of hypertension. The present review summarizes the role of nitric oxide in hypertension, focusing on the role of new NO donors, particularly the metal-based drugs and their protagonist activity in vascular function.

Biotransformation of organic nitrates by glutathione S-transferases and other enzymes: An appraisal of the pioneering work by William B. Jakoby

Organic nitrates (R-ONO₂; R, organic residue) such as nitroglycerin are used as drugs in part for more than a century. Their pharmacological use is associated with clinically relevant tolerance which is reportedly known since 1888. The underlying mechanisms of both, the mechanisms of action and the main pharmacological effect, which is vasodilatation and reduction of blood pressure, and the development of tolerance, which means increasing need of drug amount in sustained long-term therapy, are still incompletely understood. William B. Jakoby and associates were the first to report the biotransformation of organic nitrates, notably including nitroglycerin (i.e., glycerol trinitrate; GTN), by glutathione S-transferase (GST)-catalyzed conjugation of glutathione (GSH) to the nitrogen atom of one of the three nitrate groups of GTN to generate glutathione sulfenyl nitrite (glutathione thionitrate, S-nitroglutathione; GSNO₂). Jakoby's group was also the first to suggest that GSNO₂ reacts with a second GSH molecule to produce inorganic nitrite (ONO^-) and glutathione disulfide (GSSG) without the catalytic involvement of GST. This mechanism has been adopted by others to the biotransformation of GTN by mitochondrial aldehyde dehydrogenase (mtALDH-(CysSH)₂) which does not require GSH as a substrate. The main difference between these reactions is that mtALDH forms an internal thionitrate (mtALDH-(CysSH)-CysSNO₂) which releases inorganic nitrite upon intra-molecular reaction to form mtALDH disulfide (mtALDH-(CysS)₂). Subsequently, ONO^- and GSNO₂ are reduced by several proteins and enzymes to nitric oxide (NO) which is a very potent activator of soluble guanylyl cyclase to finally relax the smooth muscles thus dilating the vasculature. GSNO₂ is considered to rearrange to GSONO which undergoes further reactions including GSNO and GSSG formation. The present article is an appraisal of the pioneering work of William B. Jakoby in the area of the biotransformation of organic nitrates by GST. The two above mentioned enzymatic reactions are discussed in the context of tolerance development to organic nitrates, still a clinically relevant pharmacological concern.

Laser Doppler imaging evaluation of nitroglycerin patch application in systemic sclerosis patients

Recent studies suggest the use of topical nitroglycerin (NTG) application in systemic sclerosis (SSc)-associated Raynaud phenomenon (RP). With the current study, we aimed to characterize for the first time the microvascular response to a NTG patch (Trinipatch^® 5 mg/24 h) applied to the hand dorsum in patients with SSc using Laser Doppler imaging (LDI) at baseline and following a cold challenge. The study included 21 patients with SSc and 13 controls. Blood flow was evaluated by LDI at the level of the fingertips and metacarpus. Microvascular morphology was evaluated by nailfold capillaroscopy (NC). LDI revealed decreased fingertip baseline perfusion and a stronger vasoconstrictor response to a cold challenge in patients with SSc versus control. Metacarpal application of a NTG patch led to an increase in blood flow and hand temperature in patients with SSc. Furthermore, NTG administration led to a faster reperfusion after cold challenge. Correlation analyses revealed that the magnitude of the vasodilatory response was inversely related to baseline fingertip perfusion and hand temperature, but unrelated to the number of capillaries/mm assessed using NC. In conclusion, we provide evidence of a vasodilatory reaction following NTG patch application in patients with SSc using LDI and a protective effect against cold challenge. The magnitude of the response to NTG was related to functional, but not structural features. Our results support a further evaluation of the NTG patch as a possible therapeutic agent in SSc-associated RP.

Assessment of Vascular Dysfunction in Patients Without Obstructive Coronary Artery Disease: Why, How, and When

Ischemic heart disease secondary to coronary vascular dysfunction causes angina and impairs quality of life and prognosis. About one-half of patients with symptoms and signs of ischemia turn out not to have obstructive coronary artery disease, and coronary vascular dysfunction may be relevant. Adjunctive tests of coronary vasomotion include guidewire-based techniques with adenosine and reactivity testing, typically by intracoronary infusion of acetylcholine. The CorMicA (Coronary Microvascular Angina) trial provided evidence that routine management guided by an interventional diagnostic procedure and stratified therapy improves angina and quality of life in patients with angina but no obstructive coronary artery disease. In this paper, the COVADIS study group provide a comprehensive review of why, how, and when coronary vascular dysfunction should be assessed invasively. They discuss the rationale through a shared understanding of vascular pathophysiology and clinical evidence. They propose a consensus approach to how an interventional diagnostic procedure is performed with focus on practical aspects. Finally, the authors discuss the clinical scenarios in patients with stable and acute coronary syndromes in which measurement of coronary vascular function may be helpful for patient care.

Comparison of Nitroglycerin versus Lignocaine Spray to Attenuate Haemodynamic Changes in Elective Surgical Patients Undergoing Direct Laryngoscopy and Endotracheal Intubation: A prospective randomised study

Objectives

This study aimed to compare the effects of nitroglycerin (NTG) versus lignocaine spray in blunting the pressor response during direct laryngoscopy and endotracheal intubation.

Methods

This study was conducted between January and June 2018 in the Department of Anesthesiology, Teerthankar Mahaveer Medical College, Moradabad, India. A total of 90 elective surgical patients of American Society of Anesthesiologists physical status grades I or II were divided into three groups, comprising two treatment groups and one control group. Patients in the treatment groups received either one puff (1.5 mg/kg) of lignocaine 10% spray or one puff (400 μg) of NTG spray in the oropharynx one minute prior to the induction of anaesthesia. Haemodynamic variables and mean rate pressure product at baseline and one, two, three, four and five minutes post-induction were compared.

Results

There was a significant reduction in mean heart rate at 3–5 minutes in both treatment groups compared to the control group (P <0.050), as well as lower increases in mean arterial pressure at 1–3 minutes (P <0.050). However, at 2–4 minutes, there was a significantly greater decrease in mean systolic blood pressure in the NTG group compared to both the lignocaine and control groups (P <0.050). Moreover, a greater decrease in mean rate pressure product response at 1–5 minutes was observed in the NTG group compared to the lignocaine and control groups (P = 0.001).

Conclusion

The NTG spray was more effective than lignocaine in attenuating blood pressure increases and rate pressure product during elective laryngoscopy and intubation.

Acute Management of Hypertension Following Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is responsible for approximately 15% of strokes annually in the United States, with nearly 1 in 3 of these patients dying without ever leaving the hospital. Because this disproportionate mortality risk has been stagnant for nearly 3 decades, a main area of research has been focused on the optimal strategies to reduce mortality and improve functional outcomes. The acute hypertensive response following ICH has been shown to facilitate ICH expansion and is a strong predictor of mortality. Rapidly reducing blood pressure was once thought to induce cerebral ischemia, though has been found to be safe in certain patient populations. Clinicians must work quickly to determine whether specific patient populations may benefit from acute lowering of systolic blood pressure (SBP) following ICH. This review provides nurses with a summary of the available literature on blood pressure control following ICH. It focuses on intravenous and oral antihypertensive medications available in the United States that may be utilized to acutely lower SBP, as well as medications outside of the antihypertensive class used during the acute setting that may reduce SBP.

A New Perspective on the Nitrate-Phosphodiesterase Type 5 Inhibitor Interaction

BACKGROUND

Nitrates and nitrate-containing compounds are vasodilators used for the treatment of angina and heart failure. Phosphodiesterase type 5 inhibitors used for the treatment of erectile dysfunction are also vasodilators, and when taken together with nitrates, synergistic effects that enhance hypotensive effects may occur. Phosphodiesterase type 5 inhibitors are therefore contraindicated in patients taking organic nitrates.

METHODS AND RESULTS

A literature review was performed to provide a historical overview of different phosphodiesterase type 5 inhibitors and nitrates and their interaction. The pharmacologic characteristics of phosphodiesterase type 5 inhibitors and nitrates are reviewed, and clinical recommendations for treating cardiovascular disease in men taking phosphodiesterase type 5 inhibitors are discussed. Pharmacologic and adverse drug reactions between nitrates and phosphodiesterase type 5 inhibitors are dependent on many variables. Organic nitrates remain an absolute contraindication in men treated with phosphodiesterase type 5 inhibitors. In general, nitrates may be taken 24 hours after the last dose of short-acting phosphodiesterase type 5 inhibitors and 48 hours after the last dose of long-acting phosphodiesterase type 5 inhibitors.

CONCLUSIONS

This literature review determined that the use of phosphodiesterase type 5 inhibitors with nitrates is a contraindication, with the duration between the last dose of phosphodiesterase inhibitor and nitrate use generally varying between short- and long-acting phosphodiesterase type 5 formulations. Patients receiving nitrates who wish to use phosphodiesterase type 5 inhibitors should be educated regarding the interaction and should be evaluated to determine whether nitrate treatment can be discontinued. Further research is needed to determine how soon phosphodiesterase type 5 inhibitors can be restarted after a patient has taken a nitrate and the effect of high and low phosphodiesterase type 5 inhibitor doses on the interaction effect.

Does the Use of Nitroglycerin Patch Improve Local Anaesthetic Effects in Bier's Block? A Double-Blind Placebo Controlled Study

Aim

The aim of the study was to assess the nitroglycerin patch as a new additive to Bier's block and its impact on the effects and dose of lidocaine.

Methods

Forty patients of each sex belonging to ASA I or II underwent elective tendon repair surgeries of the forearm and hand. The patients were divided into two equal groups as follows: Group C received only lidocaine (1.5 mg/kg, 0.25%) and Group N received lidocaine (1.5 mg/kg, 0.25%) + 5 mg transcutaneous nitroglycerin patch. Onset and recovery times for sensory and motor block, visual analogue scale (VAS) scores for bandage pain, postoperative VAS score, analgesic requirements, patients' satisfaction, and surgeons' opinion were recorded.

Results

Sensory block onset time was shorter in Group N (3.80 ± 1.0) than that in Group C (5.72 ± 1.46), and motor block onset time was shorter in Group N (10.72 ± 1.93) than that in Group C (13.56 ± 1.26). Sensory block recovery time was prolonged in Group N (10.56 ± 1.12) than Group C (6.88 ± 1.45), recovery time of motor block was prolonged in Group N (13.04 ± 1.57) than Group C (11.96 ± 1.72). Bandage pain had lower VAS scores in Group N. Postoperative VAS scores showed significant differences between both groups at the following points of measurement: 30 minutes, 1 hour, and 4 hours after bandage deflation. Postoperative analgesic effect was the longest in Group N (187.20 ± 60.79 min) than Group C (51.60 ± 25.28 min). Patients' satisfaction and surgeons' opinion were better in Group N than Group C.

Conclusion

Supplementation of Bier's block with transcutaneous nitroglycerin patch reduces the lidocaine dose, the sensory and motor block onset times, VAS scores, and analgesic consumption intra- and postoperatively. Length of the block recovery times for the sensory and motor effects, duration of postoperative analgesic effect, and the first time to analgesic requirement improved the quality of Bier's block with better patients' satisfaction and surgeons' opinion and had no adverse effects.

Multidimensional Connectomics and Treatment-Resistant Schizophrenia: Linking Phenotypic Circuits to Targeted Therapeutics

Schizophrenia is a very complex syndrome that involves widespread brain multi-dysconnectivity. Neural circuits within specific brain regions and their links to corresponding regions are abnormal in the illness. Theoretical models of dysconnectivity and the investigation of connectomics and brain network organization have been examined in schizophrenia since the early nineteenth century. In more recent years, advancements have been achieved with the development of neuroimaging tools that have provided further clues to the structural and functional organization of the brain and global neural networks in the illness. Neural circuitry that extends across prefrontal, temporal and parietal areas of the cortex as well as limbic and other subcortical brain regions is disrupted in schizophrenia. As a result, many patients have a poor response to antipsychotic treatment and treatment failure is common. Treatment resistance that is specific to positive, negative, and cognitive domains of the illness may be related to distinct circuit phenotypes unique to treatment-refractory disease. Currently, there are no customized neural circuit-specific and targeted therapies that address this neural dysconnectivity. Investigation of targeted therapeutics that addresses particular areas of substantial regional dysconnectivity is an intriguing approach to precision medicine in schizophrenia. This review examines current findings of system and circuit-level brain dysconnectivity in treatment-resistant schizophrenia based on neuroimaging studies. Within a connectome context, on-off circuit connectivity synonymous with excitatory and inhibitory neuronal pathways is discussed. Mechanistic cellular, neurochemical and molecular studies are included with specific emphasis given to cell pathology and synaptic communication in glutamatergic and GABAergic systems. In this review we attempt to deconstruct how augmenting treatments may be applied within a circuit context to improve circuit integration and treatment response. Clinical studies that have used a variety of glutamate receptor and GABA interneuron modulators, nitric oxide-based therapies and a variety of other strategies as augmenting treatments with antipsychotic drugs are included. This review supports the idea that the methodical mapping of system-level networks to both on (excitatory) and off (inhibitory) cellular circuits specific to treatment-resistant disease may be a logical and productive approach in directing future research toward the advancement of targeted pharmacotherapeutics in schizophrenia.

Efficacy of nitroglycerine ointment in the treatment of pediatric anal fissure

BACKGROUND

Anal fissure is the most common anal disease in children. In the past few decades, the understanding of its pathophysiology has led to a progressive reduction in invasive procedures in favor of conservative treatment based on stool softeners and the relaxation of the anal sphincter. This randomized controlled study assessed the safety and efficacy of nitroglycerine (NTG) ointment in the treatment of pediatric anal fissure, which had not yet been proved.

PATIENTS AND METHODS

An unequal randomized controlled study included 105 pediatric patients with anal fissure who had presented to the private and outpatient clinics of the Central Teaching Hospital of Pediatrics during the period from February 2015 to May 2016. The control group consisted of 70 patients. Both groups were treated with classical conservative therapy of sitz bath, stool softener, and local anesthetic. In the second group, chemical sphincterotomy with 0.2% NTG ointment was used in 35 patients, and was applied at the anal canal twice daily for 8weeks. The primary outcomes of symptomatic improvement and healed fissure, as well as side effects, were analyzed.

RESULTS

The average age of patients was 2years (range, 4months to 5years). Patients in the NTG group had 77% symptomatic relief and 60% healed fissure compared to the control group, which had 54% and 32.8% respectively. All were statistically significant. No serious adverse effects were noticed during the treatment period.

CONCLUSION

The use of 0.2% NTG ointment is an effective therapy for anal fissure in children in terms of good healing rate and rapid symptom relief, but it has the drawback of a long treatment period, making patient compliance more difficult, in addition to the problems of tolerance and recurrence.

TYPE OF STUDY

Prospective randomized controlled study (treatment study).

LEVEL OF EVIDENCE

Type 2.

Systemic glyceryl trinitrate reduces anal sphincter tone: is there a therapeutic indication?

BACKGROUND

Nitric oxide (NO) has diverse roles as a biological messenger. [1] Topically applied nitrate donors cause relaxation of the internal anal sphincter (IAS) and facilitate healing of anal fissures [2,3]. Systemic nitrates are commonly used for the treatment of ischaemic heart disease, yet the effects of systemically administered nitrates on the smooth muscle of the IAS are unknown.

AIM

Our aim was to test the hypothesis that systemically administered nitrates at a normal dose, cause inhibition of anal sphincter activity.

METHODS

With fully informed consent, anal manometry was performed on nine volunteers. Maximum and mean anal resting pressure (representing the IAS), maximum squeeze pressure (representing the external anal sphincter), heart rate and blood pressure were measured, before and after administration of a normal 400 μg dose of sublingual glyceryl trinitrate spray.

RESULTS

Data are expressed as mean (± standard error of the mean (SEM)). In four females and five males ranging from 19 to 50 years of age, administration of GTN resulted in a significant reduction in systolic blood pressure from 138 ± 5 to 127 ± 4 mmHg, P < 0.01. Mean resting pressure, over 5 min, was significantly reduced from 70 ± 10 to 62 ± 10 mmHg P < 0.05. The maximum resting pressure was also significantly reduced from 109 ± 12 to 86 ± 10 mmHg P = 0.04. Maximum squeeze pressure, heart rate and diastolic blood pressure were not significantly reduced.

CONCLUSION

Systemic nitrates significantly inhibit internal anal sphincter function.

Hepatoprotective potential of glyceryl trinitrate against chemically induced oxidative stress and hepatic injury in rats

Glyceryl trinitrate (GTN) has been used widely as a potent vasodilator to treat heart conditions, such as angina pectoris and chronic heart failure. This study aims to elucidate the effect of exogenous nitric oxide (NO) administration, using GTN, on carbon tetrachloride (CCl4)-induced oxidative stress and liver injury in rats. The results obtained demonstrated that NO generated by the administration of GTN affords protection against CCl4-induced oxidative stress and liver injury. Administration of CCl4 resulted in a significant ( p < 0.001) increase in lipid peroxidation and tissue damage markers (aspartate and alanine transaminase and lactate dehydrogenase) release in serum. Parallel to these changes, CCl4 also caused downregulation of antioxidant enzymes including glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione-S-transferase (GST), and several fold induction in γ-glutamyl transpeptidase (GGT) activity. Subsequent administration of GTN resulted in significant ( p < 0.001) recovery of GSH-metabolizing enzymes in a dose-dependent manner. Further, administration of NO inhibitor, NG-nitro-l-arginine methyl ester (l-NAME), exacerbated CCl4-induced oxidative tissue injury. Overall, the study suggests that GTN might suppress oxidant-induced tissue injury and hepatotoxicity in rats.

Comparison between transdermal nitroglycerin and sildenafil citrate in intrauterine growth restriction: effects on uterine, umbilical and fetal middle cerebral artery pulsatility indices

OBJECTIVES

To evaluate the effects of transdermal nitroglycerin (GTN) and sildenafil citrate on Doppler velocity waveforms of the uterine (UtA), umbilical (UA) and fetal middle cerebral (MCA) arteries in pregnancies with intrauterine growth restriction (IUGR).

METHODS

This was a prospective study of 35 singleton pregnancies (gestational age, 24-31 weeks) with IUGR and abnormal UtA and UA Doppler waveforms. We compared maternal arterial blood pressure and Z-scores of the pulsatility index (PI) of UtA, UA and fetal MCA before and after application of a transdermal GTN patch (average dose, 0.4 mg/h), oral sildenafil citrate (50 mg) or placebo. Statistical analysis was performed by ANOVA for paired samples.

RESULTS

There was a significant decrease in UtA-PI after application of GTN (21.0%) and sildenafil citrate (20.4%). A significant reduction in UA-PI was also observed for both GTN (19.1%) and sildenafil citrate (18.2%). There was no difference in UtA- and UA-PI when the GTN and sildenafil groups were compared. No changes in Doppler velocimetry were observed in the placebo group and no significant change in MCA-PI was observed in any group. Maternal arterial blood pressure decreased with administration of both GTN and sildenafil citrate in those with pre-eclampsia.

CONCLUSION

The use of transdermal GTN or sildenafil citrate in pregnancies with IUGR is associated with a significant reduction in both UtA and UA Doppler PI, as well as maternal arterial blood pressure. Neither drug affected the MCA-PI. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

H89 enhances the sensitivity of cancer cells to glyceryl trinitrate through a purinergic receptor-dependent pathway

High doses of the organic nitrate glyceryl trinitrate (GTN), a nitric oxide (NO) donor, are known to trigger apoptosis in human cancer cells. Here, we show that such a cytotoxic effect can be obtained with subtoxic concentrations of GTN when combined with H89, N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulphonamide.2HCl. This synergistic effect requires the generation of reactive oxygen species (ROS) from H89 and NO from GTN treatment that causes cGMP production and PKG activation. Furthermore, the GTN/H89 synergy was attenuated by inhibition of P2-purinergic receptors with suramin and competition with ATP/UDP. By down-regulating genes with antisense oligonucleotides, P2-purinergic receptors P2X3, P2Y1, and P2Y6 were found to have a role in creating this cytotoxic effect. Thus, H89 likely acts as an ATP mimetic synergizing with GTN to trigger apoptosis in aggressive cancer cells.

A comparative evaluation of magnesium sulphate and nitroglycerine as potential adjuncts to lidocaine in intravenous regional anaesthesia

Introduction:

This randomized control trial was carried out to evaluate and compare the efficacy of magnesium sulphate and nitroglycerine (NTG) as adjuncts to lidocaine in intravenous regional anesthesia (IVRA).

Materials and Methods:

Seventy-five, ASA grade I and II patients, aged between 20–50 years, scheduled for hand and forearm surgery were selected and entered randomly into three study groups. Patients in group C received 3 mg/kg of preservative free lidocaine 2% diluted with saline to a total volume of 40 ml. Patients in group M received 3 mg/kg of preservative free lidocaine 2% mixed with 6 ml of 25% magnesium sulphate (1.5 g) diluted with saline to a total volume of 40 ml. Patients in group N received 3 mg/kg of preservative free lidocaine 2% mixed with 200 μg of nitroglycerine diluted with saline to a total volume of 40 ml. Sensory and motor block onset and recovery time, tourniquet pain onset time, intraoperative fentanyl requirement, the total number of patients requiring rescue analgesia and the time to first analgesia requirement, intra-operative and postoperative degree of analgesia were evaluated.

Results:

The sensory and motor block onset times were shorter in group M and N as compared to group C (P- = 0.004, 0.0036 for sensory block, 0.021, 0.038 for motor block. The mean time of onset of sensory block was earliest in group M and the mean time of onset of motor block was earliest in group N. Mean time of onset of tourniquet pain in the three groups was similar in groups M and N. The sensory and motor block recovery time were significantly prolonged in M and N group as compared to group C (P < 0.001). Intraoperative fentanyl requirement (P value– = 0.041), the total number of patients requiring rescue analgesia (P value = 0.009) and the time to first analgesia requirement (P value = 0.038) were lower in group M.

Conclusion:

The addition of both magnesium suphate and nitroglycerin (NTG) to lidocaine for intravenous regional anesthesia (IVRA) leads to early onset of sensory block and prolonged postoperative analgesia, with no side effects.

Glyceryl trinitrate patches-An alternative treatment for shoulder impingement syndrome

Transdermal glyceryl trinitrate patches have been investigated as an alternative therapeutic intervention for a range of tendinopathies, due to the ease of titration of dosage and the ease of their application. Glyceryl trinitrate has been inferred to reduce pain and inflammation secondary to their nitric oxide-producing action. Shoulder impingement syndrome is a soft tissue condition that manifests as anterior shoulder pain, weakness, and difficulty in daily activities. This review will evaluate the efficacy of glyceryl trinitrate patches in treating a variety of rotator cuff tendinopathies related to shoulder impingement, based on human and animal trials, and suggest its practical application in future trials and management.

The influence of nitroglycerin on the proliferation of endothelial progenitor cells from peripheral blood of patients with coronary artery disease

Endothelial progenitor cells (EPCs) are associated with vascular repairing and progression of atherosclerotic lesion. It may lead to coronary artery disease (CAD) if circulating EPCs lose their function. Continuous nitroglycerin (NTG) therapy causes increased vascular oxidative stress and endothelial dysfunction. The aim of this study was to investigate the effects of NTG on the proliferation of human peripheral blood-derived EPCs. EPC cultures, collected from 60 CAD patients and cultured for 7-12 days, were treated with different concentrations of NTG (0.0, 0.3, 1.0, 2.0, 7.5, 15.0, and 20.0 mg/l) for 72 h, respectively. The cell counts and proliferative activities of EPC; the levels of vascular endothelial growth factor-A (VEGF-A), nitric oxide (NO) and peroxynitrite (ONOO(-)) in culture medium; and the level of reactive oxygen species (ROS) in adherent cells were measured. Compared with control (0.0 mg/l NTG), the cell number and proliferative activities of EPCs were increased when treated with 1.0 mg/l NTG and reached maximum level when NTG concentration was 7.5 mg/l. However, there was a significant reduction when treated with higher doses of NTG (≥15.0 mg/l). Meanwhile, VEGF-A expression reached its maximal expression with 7.5 mg/l NTG, but gradually declined by incubation with higher doses of NTG. There was a linear relationship between NO level and NTG concentration, but no changes of ONOO(-) and ROS levels were found when EPCs were incubated with 0.3-7.5 mg/l NTG. However, ONOO(-) and ROS levels were significantly increased when incubated with 15 and 20 mg/l NTG. Our data demonstrated that moderate dose of NTG may stimulate the proliferative activities of EPCs isolated from CAD patients.

[Lidocaine alleviates propofol related pain much better than metoprolol and nitroglycerin]

BACKGROUND AND OBJECTIVES

Injection pain after propofol administration is common and may disturb patients' comfort. The aim of this study was to compare effectiveness of intravenous (iv) nitroglycerin, lidocaine and metoprolol applied through the veins on the dorsum of hand or antecubital vein on eliminating propofol injection pain.

METHOD

There were 147 patients and they were grouped according to the analgesic administered. Metoprolol (n=31, Group M), lidocaine (n=32, Group L) and nitroglycerin (n=29, Group N) were applied through iv catheter at dorsum hand vein or antecubital vein. Pain was evaluated by 4 point scale (0 - no pain, 1 - light pain, 2 - mild pain, 3 - severe pain) in 5, 10, 15 and 20th seconds. ASA, BMI, patient demographics, education level and the effect of pathways for injection and location of operations were analyzed for their effect on total pain score.

RESULTS

There were no differences between the groups in terms of total pain score (p=0.981). There were no differences in terms of total pain score depending on ASA, education level, location of operation. However, lidocaine was more effective when compared with metoprolol (p=0.015) and nitroglycerin (p=0.001) among groups. Although neither lidocaine nor metoprolol had any difference on pain management when applied from antecubital or dorsal hand vein (p>0.05), nitroglycerin injection from antecubital vein had demonstrated statistically lower pain scores (p=0.001).

CONCLUSION

We found lidocaine to be the most effective analgesic in decreasing propofol related pain. We therefore suggest iv lidocaine for alleviating propofol related pain at operations.

Lidocaine alleviates propofol related pain much better than metoprolol and nitroglycerin

BACKGROUND AND OBJECTIVES

Injection pain after propofol administration is common and may disturb patients' comfort. The aim of this study was to compare effectiveness of intravenous (iv) nitroglycerin, lidocaine and metoprolol applied through the veins on the dorsum of hand or antecubital vein on eliminating propofol injection pain.

METHOD

There were 147 patients and they were grouped according to the analgesic administered. Metoprolol (n=31, Group M), lidocaine (n=32, Group L) and nitroglycerin (n=29, Group N) were applied through iv catheter at dorsum hand vein or antecubital vein. Pain was evaluated by 4 point scale (0 - no pain, 1 - light pain, 2 - mild pain, 3 - severe pain) in 5, 10, 15 and 20th seconds. ASA, BMI, patient demographics, education level and the effect of pathways for injection and location of operations were analyzed for their effect on total pain score.

RESULTS

There were no differences between the groups in terms of total pain score (p=0.981). There were no differences in terms of total pain score depending on ASA, education level, location of operation. However, lidocaine was more effective when compared with metoprolol (p=0.015) and nitroglycerin (p=0.001) among groups. Although neither lidocaine nor metoprolol had any difference on pain management when applied from antecubital or dorsal hand vein (p>0.05), nitroglycerin injection from antecubital vein had demonstrated statistically lower pain scores (p=0.001).

CONCLUSION

We found lidocaine to be the most effective analgesic in decreasing propofol related pain. We therefore suggest iv lidocaine for alleviating propofol related pain at operations.

Transdermal nitroglycerin delivery using acrylic matrices: design, formulation, and in vitro characterization

Nitroglycerin (TNG) transdermal drug delivery systems (TDDSs) with different acrylic pressure-sensitive adhesives (PSAs) and chemical permeation enhancers (CPEs) were prepared. The effects of PSAs and CPEs types and concentrations on skin permeation and in vitro drug release from devices were evaluated using the dissolution method as well as the modified-jacketed Franz diffusion cells fitted with excised rat abdominal skin. It was demonstrated that the permeation rate or steady state flux (J_ss) of the drug through the excised rat skin was dependent on the viscosity and type of acrylic PSA as well as the type of CPE. Among different acrylic PSAs, Duro-Tak 2516 and Duro-Tak 2054 showed the highest and Duro-Tak 2051 showed the lowest J_ss. Among the various CPEs, propylene glycol and cetyl alcohol showed the highest and the lowest enhancement of the skin permeation of TNG, respectively. The adhesion properties of devices such as 180° peel strength and probe tack values were obtained. It was shown that increasing the concentration of CPE led to reduction in the adhesion property of PSA. Moreover, after optimization of the formulation, it was found that the use of 10% PG as a CPE and 25% nitroglycerin loading in Duro-Tak 2054 is an effective monolithic DIAP for the development of a transdermal therapeutic system for nitroglycerin.

Protein disulfide-isomerase interacts with soluble guanylyl cyclase via a redox-based mechanism and modulates its activity

NO binds to the receptor sGC (soluble guanylyl cyclase), stimulating cGMP production. The NO-sGC-cGMP pathway is a key component in the cardiovascular system. Discrepancies in sGC activation and deactivation in vitro compared with in vivo have led to a search for endogenous factors that regulate sGC or assist in cellular localization. In our previous work, which identified Hsp (heat-shock protein) 70 as a modulator of sGC, we determined that PDI (protein disulfide-isomerase) bound to an sGC-affinity matrix. In the present study, we establish and characterize this interaction. Incubation of purified PDI with semi-purified sGC, both reduced and oxidized, resulted in different migration patterns on non-reducing Western blots indicating a redox component to the interaction. In sGC-infected COS-7 cells, transfected FLAG-tagged PDI and PDI CXXS (redox active site 'trap mutant') pulled down sGC. This PDI-sGC complex was resolved by reductant, confirming a redox interaction. PDI inhibited NO-stimulated sGC activity in COS-7 lysates, however, a PDI redox-inactive mutant PDI SXXS did not. Together, these data unveil a novel mechanism of sGC redox modulation via thiol-disulfide exchange. Finally, in SMCs (smooth muscle cells), endogenous PDI and sGC co-localize by in situ proximity ligation assay, which suggests biological relevance. PDI-dependent redox regulation of sGC NO sensitivity may provide a secondary control over vascular homoeostasis.

Sex differences in cardiovascular drug-induced adverse reactions causing hospital admissions

AIMS

Cardiovascular disease in women is often underestimated. The effects of cardiovascular drugs differ between the sexes because of pharmacokinetic and pharmacodynamic differences. Adverse drug reactions (ADRs) within these drug classes may have serious consequences, leading to hospital admission. We aimed to study differences between men and women in hospital admissions for ADRs due to cardiovascular drugs.

METHODS

We conducted a nationwide study of all hospital admissions between 2000 and 2005 with data from the Dutch National Medical Register. Relative risks were calculated of hospital admissions due to ADRs to the different cardiovascular drug groups for women compared with men. By an ecological design, risks were adjusted for the total number of Dutch inhabitants and the total number of prescriptions.

RESULTS

In total, 14 207 of the hospital admissions (34% of all ADR-related admissions) were attributed to cardiovascular drugs [7690 in women (54%; 95% confidence interval 53-55%)]. 'Anticoagulants and salicylates' (n= 8988), 'high- and low-ceiling diuretics' (n= 2242) and 'cardiotonic glycosides' (n= 932) were responsible for the majority of the ADR-related hospital admissions. The most pronounced sex differences were seen in users of low-ceiling diuretics (relative risk 4.02; 95% confidence interval 3.12-5.19), cardiotonic glycosides (relative risk 2.38; 95% confidence interval 2.06-2.74), high-ceiling diuretics (relative risk 2.10; 95% confidence interval 1.91-2.32) and coronary vasodilators (relative risk 0.77; 95% confidence interval 0.65-0.91).

CONCLUSIONS

Clear sex differences exist in ADRs requiring hospital admission for different cardiovascular drug groups. Sex differences should be taken into account in the prescription and evaluation of drugs.

The analgesic effect of nitroglycerin added to lidocaine on quality of intravenous regional anesthesia in patients undergoing elective forearm and hand surgery

PURPOSE

To evaluate the effect of nitroglycerine (NTG) on sensory and motor block onset and recovery time as well as the quality of tourniquet pain relief, when added to lidocaine (LID) for intravenous regional anesthesia in elective forearm and hand surgery.

METHODS

A randomized double-blinded clinical trial was performed on 40 patients that were randomly allocated into two groups received lidocaine 3 mg/kg with NTG 200 µg or received only lidocaine 3 mg/kg as the control.

RESULTS

There was no difference between the two study groups in hemodynamic parameters before tourniquet inflation, at any time after inflation and after its deflation. There was no difference in the mean of pain score over time between the two groups. The onset time of sensory and motor blockades was shorter in the group received both LID and NTG. The mean recovery time of sensory blockade was longer in the former group. The frequency of opioid injections was significantly lower in those who administered LID and NTG.

CONCLUSION

The adjuvant drug of NTG when added to LID is effective in improving the overall quality of anesthesia, shortening onset time of both sensory and motor blockades, and stabling homodynamic parameters in hand and forearm surgery.

Successful management of contrast medium extravasation injury through stellate ganglion block and intra-arterial nitroglycerin

We describe the successful management of extravasation injury to the left hand by contrast medium with stellate ganglion block and intra-arterial nitroglycerin in a patient which befell during contrast-enhanced imaging. The incidence of contrast-medium extravasation injury is increasing because of the convenience and availability of contrast-enhanced imaging and ease of injection access. Extravasation of contrast medium may results in severe pain, erythema, cyanosis, and edema or even skin necrosis, which is largely related to the ionization, osmolarity, and volume of the contrast medium. The conservative treatment is often adequate in small amount extravasation, but if the extravasation is overwhelming further energetic management is mandatory. A 29-year-old man was brought to our emergency because of diffuse abdominal pain and he was arranged to receive intravenous contrast media enhanced abdominal computed tomography for diagnosis. Ruptured appendicitis with abscess formation was suspected; then the patient underwent emergent appendectomy and drainage of the abscess. However, severe swelling and cyanotic change that radiated from the intravenous catheter insertion site in every direction over the entire dorsum of the left hand were noted after the surgery. Contrast-medium extravasation injury was highly contemplated and a left stellate ganglion block was performed immediately for relief of symptoms. The consulting surgeon ruled out compartment syndrome, but advised emergent left upper limb arteriography, which revealed signs of vasospasm with high intravascular pressure of the left distal ulnar and radial arteries; thus nitroglycerin was injected into left distal ulnar and radial arteries for relief of vasospasm. The clinical symptoms were improved after the above managements and the patient was discharged 7 days later without any sequela.

Transdermal nitroglycerin in patients with severe pre-eclampsia with placental insufficiency: effect on uterine, umbilical and fetal middle cerebral artery resistance indices

OBJECTIVES

To evaluate the effect of transdermal nitroglycerin on Doppler velocity waveforms of the uterine, umbilical and fetal middle cerebral arteries in patients with severe pre-eclampsia.

METHODS

This was a prospective study of 30 singleton pregnancies (gestational age range: 24-31 weeks) with severe pre-eclampsia and abnormal uterine and umbilical artery Doppler waveforms. We compared maternal blood pressure as well as the resistance index (RI) and the pulsatility index (PI) of the uterine, umbilical and fetal middle cerebral arteries before and after application of a transdermal nitroglycerin patch (average dose 0.4 mg/h) for a period of 3 days. Intra-day comparisons before and after administration of nitroglycerin and a comparison between days 0 (no patch) and 3 after administration of the first dose of nitroglycerin were performed using ANOVA for paired samples.

RESULTS

A significant decrease in the PI and RI of the uterine (25.3 ± 4.9% and 21.2 ± 6.2%, respectively, P < 0.001) and umbilical (23.1 ± 6.9% and 19.7 ± 6.1%, respectively, P < 0.001) arteries was noted when comparing the first day without medication against the third day with the patch. No significant change in the PI and RI of the middle cerebral artery was observed. The mean arterial blood pressure decreased from 119.5 ± 4.5 mmHg to 114.8 ± 4.4 mmHg (P < 0.05).

CONCLUSION

The use of transdermal nitroglycerin in patients with severe pre-eclampsia is associated with a significant reduction in the RI and PI of the uterine and umbilical arteries, as well as of maternal blood pressure. Transdermal nitroglycerin does not affect the RI and PI of the fetal middle cerebral artery.

Does the use of ketamine or nitroglycerin as an adjuvant to lidocaine improve the quality of intravenous regional anesthesia?

Aims:

To compare and evaluate the effect of adding ketamine or nitroglycerin (NTG) as adjuncts to lidocaine for intravenous regional anesthesia (IVRA) on intraoperative and postoperative analgesia, sensorial and motor block onset times, and tourniquet pain.

Settings and Design:

A prospective, randomized, double-blind study was carried out.

Materials and Methods:

Seventy-five patients undergoing hand surgery were divided into three groups as follows: control group receiving lidocaine 2%, LK group receiving lidocaine 2% with ketamine, and LN group administered lidocaine 2% with NTG. Sensory and motor blocks' onset and recovery times were recorded. Visual analog scale (VAS) for tourniquet pain was measured after tourniquet application and it was also used to measure postoperative pain. Analgesic consumption for tourniquet pain and postoperatively were recorded.

Results:

Sensory block onset times were shorter in the LK (4.4 ± 1.2 minutes) and LN (3.5 ± 0.9 minutes) groups compared with the control group (6.5 ± 1.1 minute) (P < 0.0001) and motor block onset times were shorter in the LK (7.3 ± 1.6 minutes) and LN (3.6 ± 1.2 minutes) groups compared with the control group (10.2 ± 1.5 minutes) (P< 0.0001). Sensory recovery time prolonged in the LK (6.7 ± 1.3 minutes) and LN (6.9 ± 1.1 minutes) groups compared with the control group (5.3 ± 1.4 minutes) (P = 0.0006 and < 0.0001, respectively). Motor recovery time prolonged in the LK (8.4 ± 1.4 minutes) and LN (7.9 ± 1.1 minutes) groups compared with the control group (7.1 ± 1.3 minutes) (P = 0.0014 and 0.023, respectively). The sensory and motor block onset times were also shorter in LN group than in the LK group (3.5 ± 0.9 versus 4.4 ± 1.2 minutes, P=0.004; and 3.6 ± 1.2 versus 7.3 ± 1.6 minutes, P < 0.0001, respectively). The amount of fentanyl required for tourniquet pain was less in adjuvant groups when compared with control group. It was 13.6 ± 27.9 and 27.6 ± 34.9 µg in LK group and LN groups, respectively, versus 54.8 ± 28 µg in the control group. VAS scores of tourniquet pain were higher at 10, 20, 30, 40 minutes in the control group compared with the other study groups (P < 0.0001). It was also higher in LN group compared with LK group at 30 and 40 minutes (P < 0.001). Postoperative VAS scores were higher for the first 4 h in control group compared with the other study groups (P< 0.0001).

Conclusions:

The adjuvant drugs (ketamine or NTG) when added to lidocaine in IVRA were effective in improving the overall quality of anesthesia, reducing tourniquet pain, increasing tourniquet tolerance and improving the postoperative analgesia in comparison to the control group. Ketamine as an adjuvant produced better tolerance to tourniquet than the other groups. NTG as an adjuvant produced faster onset of sensory and motor blockades in comparison to other groups.

Developmental toxicity of glyceryl trinitrate in quail embryos

BACKGROUND

Although glyceryl trinitrate (GTN) is used extensively to treat angina and heart failure, little is known about its effects on the conceptus during organogenesis. The goal of these studies was to investigate the effects of GTN in a model organism, the quail (Coturnix coturnix japonica) embryo.

METHODS

To identify the effects of GTN on quail embryo development, fertilized quail eggs (n = 10-12 eggs/group) were injected with GTN (0, 4.4, 44, or 440 μM) at Hamburger-Hamilton (HH) stage 0, 9, or 19 and examined 7 days later. Next, HH 9 embryos were injected with GTN (0, 0.88, 4.4, 8.8, 44, 88, and 440 μM, in 20 μL per egg) and examined 24-hours, 48-hours, or 72-hours postinjection. Finally, the developing eye on one side was exposed to GTN (44 μM) ex ovo and the tissue was probed for the presence of nitrated proteins.

RESULTS

In ovo GTN exposure induced a dose-dependent increase in the number of malformed viable quail embryos with a maximal effect in HH 9 embryos. Microphthalmia, craniofacial, heart, and neural tube defects were elevated in GTN-exposed embryos. An increase in nitrated proteins was observed in the developing eye region of embryos exposed ex ovo to GTN.

CONCLUSIONS

GTN treatment induced a variety of malformations in quail embryos. The presence of nitrated proteins suggests that organic nitrates, such as GTN, generate reactive nitrogen species. We hypothesize that GTN perturbations in the redox status of the embryo may underlie its developmental toxicity.

Nitroglycerin alters matrix remodeling proteins in THP-1 human macrophages and plasma metalloproteinase activity in rats

Several studies suggested that long-term nitrate therapy may produce negative outcomes in patient mortality and morbidity. A possible mechanism may involve nitrate-mediated activation of various extracellular matrix (ECM) proteases, particularly matrix metalloproteinase-9 (MMP-9), and adhesion molecules in human macrophages, leading to the destabilization of atherosclerotic plaques. We examined the gene and protein regulating effects on THP-1 human macrophages by repeated exposure to therapeutically relevant concentrations of nitroglycerin (NTG) and possible involvement of nuclear factor (NF)-κB signaling mechanism in mediating some of these observed effects. THP-1 human macrophages repeatedly exposed to NTG (at 10 nM, added on days 1, 4 and 7) exhibited extensive alterations in the expression of multiple genes encoding ECM proteases and adhesion molecules. These effects were dissimilar to those produced by a direct nitric oxide donor, diethylenetriamine NONOate. NTG exposure significantly up-regulated NF-κB DNA nuclear binding activity and MMP-9 protein expression, and reduced tissue inhibitor of metalloproteinase-1 (TIMP-1) expression; these effects were abrogated in the presence of the NF-κB inhibitor parthenolide (a chemical inhibitor derived from the feverfew plant). Further, we examined whether our in vitro findings (an elevated MMP-9/TIMP-1 ratio and gelatinase activity) can be translated to in vivo effects, in a rat model. Sprague-Dawley rats exposed continuously to NTG subcutaneously for 8 days via mini-osmotic pumps showed significant induction of plasma MMP-9 dimer concentrations and the expression of a complex of MMP-9 with lipocalin-2 or neutrophil gelatinase associated lipocalin (NGAL). Plasma gelatinase activity was significantly increased by NTG over the entire study period, attaining peak elevation at day 6. Plasma TIMP-1 protein was down-regulated significantly by day 2 and days 4-7 in the NTG-treated rats. Pharmacokinetic monitoring of NTG and its dinitrate metabolites indicated that concentrations were well within therapeutic levels observed in humans. Our studies indicate that clinically relevant concentrations of NTG not only altered ECM matrix by changing the expression of multiple genes that govern cellular integrity, affecting cellular MMP-9/TIMP-1 balance in THP-1 human macrophages possibly via NF-κB activation, but also led to systemic changes in MMP-9/TIMP-1 expression and gelatinase activity in rats. These effects may contribute to extracellular matrix degradation and possible atherosclerotic plaque destabilization.

Nitroglycerin in the prevention of post-ERCP pancreatitis: a meta-analysis

The objective of this research paper is to evaluate the effect of prophylactic nitroglycerin in the prevention of post-endoscopic retrograde cholangiopancreatography (ERCP) pancreatitis (PEP) by performing a meta-analysis of randomized controlled trials (RCTs). Electronic databases, including PubMed, EMBASE, the Cochrane library, and the Science Citation Index, were searched to retrieve relevant trials. Outcome measures were the incidence of PEP. Four RCTs, enrolling a total of 856 patients, were included. Meta-analysis of these trials indicated a significant association between the use of nitroglycerin and the reduction of PEP (RR 0.60; 95%CI: 0.39-0.92; P = 0.02). However, subsequent sensitive analysis failed to confirm that nitroglycerin was statistically superior to a placebo in reducing PEP (RR 0.68; 95%CI: 0.41-1.11; P = 0.12). Based on the limitations in this meta-analysis, prophylactic use of nitroglycerine for all patients who underwent ERCP is not recommended. Further clinical trials are required to confirm the effect of nitroglycerin in the prevention of PEP.

Degradation of leucine zipper-positive isoform of MYPT1 may contribute to development of nitrate tolerance

AIMS

A depressed cGMP-dependent protein kinase (PKG) activity is implicated in nitrate tolerance. The present study determines whether the leucine zipper-positive (LZ+) isoform of myosin phosphatase target subunit 1 (MYPT1), a key target protein for PKG actions, is involved in the development of nitrate tolerance.

METHODS AND RESULTS

Nitrate tolerance in in vitro preparations was obtained by a 24 h incubation with nitroglycerin (NTG). Nitrate tolerance in in vivo preparations was obtained by subcutaneous injection of mice with NTG, and the aortas were used. Protein levels of total MYPT1, MYPT1 (LZ+), PP1Cdelta, myosin light chain (MLC), and phosphorylated MLC were determined by Western blot analysis. Isometric vessel tension was determined by an organ chamber technique. Protein levels of MYPT1 (LZ+), but not of PP1Cdelta, were significantly reduced in in vitro and in vivo nitrate-tolerant arteries. The decrease in the MYPT1 (LZ+) protein level of coronary artery was also induced by a nitric oxide donor and a cGMP analogue, which was prevented by the inhibitors of soluble guanylyl cyclase and PKG. The decrease in MYPT1 (LZ+) protein levels was not affected by the inhibitor of protein synthesis, but was prevented by the inhibitors of proteasomes. The diminished inhibition of dephosphorylation of MLC as well as the attenuated relaxation of porcine coronary artery and mouse aorta to NTG was improved by proteasome inhibitors.

CONCLUSION

This study demonstrates that a reduction in the protein level of MYPT1 (LZ+) is involved in nitrate tolerance. This may result in part from a proteasome-dependent degradation of MYPT1 (LZ+).

A theoretical model for transdermal drug delivery from emulsions and its dependence upon formulation

This article presents a theoretical model of transdermal drug delivery from an emulsion-type vehicle that addresses the vehicle heterogeneity and incorporates the prediction of drug transport parameters as function of the vehicle composition. The basic mass transfer model considers interfacial and diffusion resistances within the emulsion and partition/diffusion phenomena across two skin compartments in series. Drug transport parameters are predicted as follows: partition coefficients are derived from regular solutions theory, drug diffusivity in the continuous phase is computed from a free volume theory with segmental motion, and permeability of the surfactant layer around droplets is estimated based on a free surface area model. These relationships are incorporated within the basic mass transfer model, so that the overall model is able to predict temporal profiles of drug release from the vehicle and of drug concentration in plasma, as a function of vehicle composition. In this way, the proposed model provides a sound physicochemical basis to support the development of new formulations and the planning of experiments. A simulated case study regarding a nitroglycerin ointment is presented in detail, illustrating how thermodynamic and kinetic factors inherent to the emulsion vehicle can modulate drug release and subsequent systemic absorption.

Nitroglycerin-induced S-nitrosylation and desensitization of soluble guanylyl cyclase contribute to nitrate tolerance

Nitrates such as nitroglycerin (GTN) and nitric oxide donors such as S-nitrosothiols are clinically vasoactive through stimulation of soluble guanylyl cyclase (sGC), which produces the second messenger cGMP. Development of nitrate tolerance, after exposure to GTN for several hours, is a major drawback to a widely used cardiovascular therapy. We recently showed that exposure to nitric oxide and to S-nitrosothiols causes S-nitrosylation of sGC, which directly desensitizes sGC to stimulation by nitric oxide. We tested the hypothesis that desensitization of sGC by S-nitrosylation is a mechanism of nitrate tolerance. Our results established that vascular tolerance to nitrates can be recapitulated in vivo by S-nitrosylation through exposure to cell membrane-permeable S-nitrosothiols and that sGC is S-nitrosylated and desensitized in the tolerant, treated tissues. We next determined that (1) GTN treatment of primary aortic smooth muscle cells induces S-nitrosylation of sGC and its desensitization as a function of GTN concentration; (2) S-nitrosylation and desensitization are prevented by treatment with N-acetyl-cysteine, a precursor of glutathione, used clinically to prevent development of nitrate tolerance; and (3) S-nitrosylation and desensitization are reversed by cessation of GTN treatment. Finally, we demonstrated that in vivo development of nitrate tolerance and crosstolerance by 3-day chronic GTN treatment correlates with S-nitrosylation and desensitization of sGC in tolerant tissues. These results suggest that in vivo nitrate tolerance is mediated, in part, by desensitization of sGC through GTN-dependent S-nitrosylation.

Constitutive nitric oxide synthase activation is a significant route for nitroglycerin-mediated vasodilation

The physiological effects of nitroglycerin as a potent vasodilator have long been documented. However, the molecular mechanisms by which nitroglycerin exerts its biological functions are still a matter of intense debate. Enzymatic pathways converting nitroglycerin to vasoactive compounds have been identified, but none of them seems to fully account for the reported clinical observations. Here, we demonstrate that nitroglycerin triggers constitutive nitric oxide synthase (NOS) activation, which is a major source of NO responsible for low-dose (1-10 nM) nitroglycerin-induced vasorelaxation. Our studies in cell cultures, isolated vessels, and whole animals identified endothelial NOS activation as a fundamental requirement for nitroglycerin action at pharmacologically relevant concentrations in WT animals.

Smooth Muscle Dysfunction in Patients Older than 54 Years of Age with Objective Evidence of Arteriosclerosis

OBJECTIVE

This investigation was designed to assess the relationship between flow-mediated vasodilatation (FMD) and nitroglycerin (NTG)-mediated vasodilatation (NMD) with atherosclerotic risk factors.

METHODS

FMD and NMD were measured in 75 subjects including 57 patients with atherosclerotic disease (AAA/PAOD=30/27, age 72+/-7 years) and 18 controls. Brachial response to hyperemia and NTG were measured every minute after cuff deflation and NTG administration.

RESULTS

In the 75 subjects, responses to NTG showed a sigmoid curve. Only 2 cases reached maximal diameter within 4 minutes after NTG, and 90% of the cases reached maximal diameter at 6 minutes or later (7.5+/-2.0 minutes). In patients with atherosclerotic disease, a multiple regression analysis showed higher FMD was associated with higher NMD, and higher NMD was associated with smaller vessel size, lower systolic blood pressure, higher FMD, lower carotid maximal IMT, lower serum levels of insulin, and lower HOMA-IR.

CONCLUSIONS

In subjects older than 54, NMD measured at 3 or 4 minutes after NTG administration would underestimate the NTG-dependent vasodilatation. NMD measured with the maximal responded diameter was associated with atherosclerotic risk factors, and it is therefore considered to be an important parameter in patients with atherosclerotic disease.

Role of cGMP-dependent protein kinase in development of tolerance to nitroglycerine in porcine coronary arteries

BACKGROUND AND PURPOSE

The cGMP-dependent protein kinase (PKG) is a key enzyme for nitrovasodilator-induced vasodilation. The present study was to determine its role in nitrate tolerance.

EXPERIMENTAL APPROACH

isolated porcine coronary arteries were incubated for 24 h with nitroglycerin (NTG) and their relaxant responses were determined. PKG activity was assayed by measuring the incorporation of (32)P into BPDEtide. PKG protein was determined by Western blotting and PKG mRNA by real-time PCR.

KEY RESULTS

A 24 h incubation with NTG attenuated relaxation of coronary arteries to NTG, which was associated with decreased PKG activity. The nitrate tolerance induced with NTG at 10(-7) M was affected by a scavenger of reactive oxygen species and the tolerance induced with NTG at 10(-6) and 10(-5) M showed cross-tolerance to DETA NONOate and 8-Br-cGMP (a cell permeable cGMP analogue). PKG protein and mRNA were down-regulated by a 24 h incubation with NTG at 10(-5) M but not at 10(-7) M. Acute exposure to exogenous superoxide inhibited PKG activity stimulated by NTG at 10(-7) M but not at 10(-5) M. Superoxide had no effect on PKG activity stimulated with exogenous cGMP.

CONCLUSIONS AND IMPLICATIONS

Nitrate tolerance induced by NTG at low concentrations may result from an increased production of reactive oxygen species acting on sites upstream of PKG. The tolerance induced by NTG at higher concentrations may be in part due to suppression of PKG expression resulting from sustained activation of the enzyme. These distinct mechanisms of nitrate tolerance may be of clinical significance.