Augmented Pulmonary Vasoconstrictor Reactivity after Chronic Hypoxia Requires Src Kinase and Epidermal Growth Factor Receptor Signaling

Chronic hypoxia augments pressure- and agonist-induced pulmonary vasoconstriction through myofilament calcium sensitization. NADPH oxidases contribute to the development of pulmonary hypertension, and both epidermal growth factor receptor and Src kinases can regulate NADPH oxidase. We tested the hypothesis that Src-epidermal growth factor receptor (EGFR) signaling mediates enhanced vasoconstrictor sensitivity after chronic hypoxia through NADPH oxidase-derived superoxide generation. Protocols employed pharmacological inhibitors in isolated, pressurized rat pulmonary arteries to examine the contribution of a variety of signaling moieties to enhanced vascular tone after chronic hypoxia. Superoxide generation in pulmonary arterial smooth muscle cells was assessed using the fluorescent indicator dihydroethidium. Indices of pulmonary hypertension were measured in rats treated with the EGFR inhibitor gefitinib. Inhibition of NADPH oxidase, Rac1 (Ras-related C3 botulinum toxin substrate 1), and EGFR abolished pressure-induced pulmonary arterial tone and endothelin-1 (ET-1)-dependent calcium sensitization and vasoconstriction after chronic hypoxia. Consistently, chronic hypoxia augmented ET-1-induced superoxide production through EGFR signaling, and rats treated chronically with gefitinib displayed reduced right ventricular pressure and diminished arterial remodeling. Src kinases were also activated by ET-1 after chronic hypoxia and contributed to enhanced basal arterial tone and vasoconstriction in response to ET-1. A role for matrix metalloproteinase 2 to mediate Src-dependent EGFR activation is further supported by our findings. Our studies support a novel role for an Src kinase-EGFR-NADPH oxidase signaling axis to mediate enhanced pulmonary vascular smooth muscle Ca2+ sensitization, vasoconstriction, and pulmonary hypertension after chronic hypoxia.

Pharmacokinetics and pharmacodynamics of dexmedetomidine-induced vasoconstriction in healthy volunteers

AIMS

Alpha-2 agonists are direct peripheral vasoconstrictors, which achieve these effects by activating vascular smooth muscle alpha-2 adrenoceptors. The impact of this response during dexmedetomidine infusion remains poorly quantified. Our goal was to investigate the pharmacokinetic (PK) and pharmacodynamic (PD, vasoconstriction) effects of a computer-controlled dexmedetomidine infusion in healthy volunteers.

METHODS

After local ethics committee approval, we studied 10 healthy volunteers. To study the peripheral vasoconstrictive effect of dexmedetomidine without concurrent sympatholytic effects, sympathetic fibres were blocked with a brachial plexus block. Volunteers received a dexmedetomidine target-controlled infusion for 15 min, to a target concentration of 0.3 ng ml-1 . Arterial blood samples were collected during and for 60 min after dexmedetomidine infusion for PK analysis. Peripheral vasoconstriction (PD) was assessed using finger photoelectric plethysmography. PK/PD analysis was carried out using nonlinear mixed-effect models.

RESULTS

We found that the computer-controlled infusion pump delivered mean concentrations greater than 0.3 ng ml-1 over the 15-min infusion duration. The peripheral vasoconstrictive effect correlated with dexmedetomidine plasma concentrations during and after the infusion. A three-compartment model provided a better fit to the data than a two-compartment model.

CONCLUSIONS

We found that dexmedetomidine-induced vasoconstriction is concentration dependent over time. Dexmedetomidine PK were best estimated by a three-compartment model with allometric scaling. Our results may contribute to future modelling of dexmedetomidine-induced haemodynamic effects.

Pharmacokinetics of Lidocaine Hydrochloride Administered with or without Adrenaline for the Paravertebral Brachial Plexus Block in Dogs

Adrenaline is known to prolong the duration of local anesthesia but its effects on the pharmacokinetic processes of local anesthetic drugs are not fully understood. Our objective was to develop a compartmental model for quantification of adrenaline’s impact on the pharmacokinetics of perineurally-injected lidocaine in the dog. Dogs were subjected to paravertebral brachial plexus block using lidocaine alone or adrenalinated lidocaine. Data was collected through a prospective, randomised, blinded crossover protocol performed over three periods. Blood samples were collected during 180 minutes following block execution. Compartmental pharmacokinetic models were developed and their goodness-of-fit were compared. The lowering effects of adrenaline on the absorption of lidocaine were statistically determined with one-sided tests. A one-compartment disposition model with two successive zero-order absorption processes best fitted our experimental data. Adrenaline decreased the peak plasma lidocaine concentration by approximately 60% (P < 0.001), decreased this local anesthetic’s fast and slow zero-order absorption rates respectively by 50% and 90% (P = 0.046, and P < 0.001), which respective durations were prolonged by 90% and 1300% (P < 0.020 and P < 0.001). Lidocaine demonstrated a previously unreported atypical absorption profile following its paravertebral injection in dogs. Adrenaline decreased the absorption rate of lidocaine and prolonged the duration of its absorption.

Management of delayed cerebral ischemia after subarachnoid hemorrhage

For patients who survive the initial bleeding event of a ruptured brain aneurysm, delayed cerebral ischemia (DCI) is one of the most important causes of mortality and poor neurological outcome. New insights in the last decade have led to an important paradigm shift in the understanding of DCI pathogenesis. Large-vessel cerebral vasospasm has been challenged as the sole causal mechanism; new hypotheses now focus on the early brain injury, microcirculatory dysfunction, impaired autoregulation, and spreading depolarization. Prevention of DCI primarily relies on nimodipine administration and optimization of blood volume and cardiac performance. Neurological monitoring is essential for early DCI detection and intervention. Serial clinical examination combined with intermittent transcranial Doppler ultrasonography and CT angiography (with or without perfusion) is the most commonly used monitoring paradigm, and usually suffices in good grade patients. By contrast, poor grade patients (WFNS grades 4 and 5) require more advanced monitoring because stupor and coma reduce sensitivity to the effects of ischemia. Greater reliance on CT perfusion imaging, continuous electroencephalography, and invasive brain multimodality monitoring are potential strategies to improve situational awareness as it relates to detecting DCI. Pharmacologically-induced hypertension combined with volume is the established first-line therapy for DCI; a good clinical response with reversal of the presenting deficit occurs in 70 % of patients. Medically refractory DCI, defined as failure to respond adequately to these measures, should trigger step-wise escalation of rescue therapy. Level 1 rescue therapy consists of cardiac output optimization, hemoglobin optimization, and endovascular intervention, including angioplasty and intra-arterial vasodilator infusion. In highly refractory cases, level 2 rescue therapies are also considered, none of which have been validated. This review provides an overview of current state-of-the-art care for DCI management.

Nonvasoconstrictive hemoglobin particles as oxygen carriers

Artificial oxygen carriers, favorably hemoglobin-based oxygen carriers (HBOCs), are being investigated intensively during the last 30 years with the aim to develop a universal blood substitute. However, serious side effects mainly caused by vasoconstriction triggered by nitric oxide (NO) scavenging due to penetration of nanosized HBOCs through the endothelial gaps of the capillary walls and/or oxygen oversupply in the precapillary arterioles due to their low oxygen affinity led to failure of clinical trials and FDA disapproval. To avoid these effects, HBOCs with a size between 100 and 1000 nm and high oxygen affinity are needed. Here we present for the first time unique hemoglobin particles (HbPs) of around 700 nm with high oxygen affinity and low immunogenicity using a novel, highly effective, and simple technique. The fabrication procedure provides particles with a narrow size distribution and nearly uniform morphology. The content of hemoglobin (Hb) in the particles corresponded to 80% of the Hb content in native erythrocytes. Furthermore, we demonstrate a successful perfusion of isolated mouse glomeruli with concentrated HbP suspensions in vitro. A normal, nonvasoconstrictive behavior of the afferent arterioles is observed, suggesting no oxygen oversupply and limited NO scavenging by these particles, making them a highly promising blood substitute.

Effects of a supratherapeutic dose of investigational orally inhaled dihydroergotamine (MAP0004) on QT interval: a randomized, double-blind, active- and placebo-controlled crossover study in healthy volunteers

BACKGROUND

MAP0004 is an orally inhaled investigational drug containing dihydroergotamine (DHE). Although DHE has been used for 60 years with no reported cardiac arrhythmias, a thorough QT study had not previously been performed with DHE.

OBJECTIVE

The objective of this study was to assess the effects of MAP0004 on the QT interval as required for regulatory approval of a new product.

METHODS

This randomized, double-blind, placebo-controlled, 3-period crossover study enrolled healthy volunteers. Subjects were assigned to receive, in randomized sequence, MAP0004 at a supratherapeutic dose (3-fold the clinically effective dose) (3.0 mg), moxifloxacin 400 mg, or inactive vehicle, each administered with 1 placebo capsule. Triplicate ECGs were performed continuously at baseline (day 0), before dosing, and over 24 hours after dosing in each treatment period. The effect on the QT interval was assessed using the Fridericia (QTcF) and individualized (QTcI) correction formulas.

RESULTS

Fifty-four healthy adults (20 men, 34 women; mean age, 28 years) completed the trial and had measurable plasma levels of DHE after MAP0004 administration. The largest observed mean difference in QTcI between MAP0004 and placebo was 0.08 msec, and the largest 1-sided 95% upper confidence bound was 2.24 msec, both at 30 minutes after dosing. In contrast, moxifloxacin increased the mean QTcI between 9.57 and 11.28 msec relative to placebo, with a 1-sided lower 95% CL between 7.23 and 8.96 msec, confirming that the assay sensitivity was sufficient to detect MAP0004-related effects. Nausea (27.8%) was common following MAP0004 administration but apparently did not influence the QTc interval.

CONCLUSIONS

A supratherapeutic dose of MAP0004 was not associated with prolonged QTc intervals. At the proposed clinical dose (1.0 mg), MAP0004 is unlikely to affect the QT interval. MAP0004 and its primary metabolite showed no evidence for prolongation of the QTc interval in healthy subjects according to the criteria required from regulatory agencies. ClinicalTrials.gov identifier: NCT01191723.

Pathogenesis of pre-eclampsia: marinobufagenin and angiogenic imbalance as biomarkers of the syndrome

Pre-eclampsia (preE), a pregnancy disorder with the de novo onset of hypertension and proteinuria after 20 weeks of gestation, has multiple triggers that initiate pathophysiologic mechanisms. This review addresses translational aspects of preE by synthesizing information on preE pathogenesis, describing diagnostic biomarkers that predict disease, and suggesting strategies to lessen adverse outcomes. Key to this understanding is the role of cardiotonic bufodienolides, with marinobufagenin (MBG) as the prototype, and angiogenic factors in preE pathogenesis. Data from a rat model believed to mimic human preE show that urinary excretion of MBG increases before the onset of hypertension and proteinuria and that affected animals have an increased vascular leakage and blood brain barrier permeability. Angiogenic imbalance occurs with the onset of the syndrome in this model. Also, we report that MBG levels in preE patients exceed those in normal pregnancy and that angiogenic factors are altered in patients showing signs and symptoms of overt disease. In vitro administration of MBG inhibits cytotrophoblast function and triggers hyperpermeability in endothelial cell monolayers. We advance the hypotheses that MBG precedes preE; MBG causes disruption of tight junction proteins leading to vascular leak via activation of MAPK which triggers apoptotic mechanisms resulting in further endothelial dysfunction leading to edema with the release of angiogenic factors. This review provides new evidence about the role of MBG and vasoactive intermediates in preE pathogenesis including the neurologic sequela and may reveal new therapeutic targets for the prevention of preE complications.

Evidence-based neonatal pharmacotherapy: postnatal corticosteroids

Corticosteroids are used in the neonatal intensive care unit primarily to treat two conditions: bronchopulmonary dysplasia (BPD) and hypotension (cardiovascular insufficiency). Historically, high-dose dexamethasone was used for BPD, but its use was later associated with adverse neurodevelopmental outcomes and decreased substantially. Data from randomized controlled trials regarding efficacy and safety of lower-dose dexamethasone therapy are insufficient to recommend its use. Hydrocortisone may be an alternative to dexamethasone, but again data are insufficient to support use. Hydrocortisone therapy is increasingly used to treat hypotension in critically ill newborns; however, the outcomes of this therapy must be evaluated in randomized trials.

Pressor doses of vasopressin result in only transient elevations in plasma peptide levels

We recently reported that neuronostatin, a novel neuropeptide, biphasically increased mean arterial pressure, first through the activation of the sympathetic nervous system followed by the release of vasopressin. In those experiments, we found that centrally administered neuronostatin increased plasma vasopressin levels only 2-3 times greater than levels observed in saline-treated controls, and that the increase in mean arterial pressure (approximately 15 mm Hg) could be blocked by pretreatment with a V1-vasopressin antagonist. Here we report the relationship between two to three fold elevations in plasma vasopressin levels and concomitant changes in mean arterial pressure in conscious, unrestrained male rats. We injected increasing doses of vasopressin (5, 20, and 100 ng/kg, intra-arterially) and measured both changes in plasma vasopressin levels and the elevation in mean arterial pressure achieved. At 5-min post injection, plasma levels of vasopressin and mean arterial pressures were similar to those observed following central neuronostatin administration in our earlier study. Thus we conclude that small increases in circulating vasopressin levels can result in significant elevations in mean arterial pressure at least in the conscious rat.

Changing the pathophysiology of solid tumours: The potential of TNF and other vasoactive agents

Solid tumour therapy with chemotherapeutic drugs is hampered by a number of factors resulting in poor results and failure of initially promising drugs. From the application of Tumour Necrosis Factor alpha in the melphalan-based Isolated Limb perfusion some lessons could be learned. Most importantly, combination of treatment approaches, certainly when multiple targets are involved, increases the effectiveness of the therapy. Clinical outcome may improve dramatically when the tumour pathophysiology is changed in such a way that co-administered chemotherapeutics are more active or are capable of reaching the tumour cells better. Here some of the methodologies and drug combinations which improve solid tumour therapy through acting on the tumour pathophysiology are discussed.

Propofol infusion syndrome: update of clinical manifestation and pathophysiology

Propofol infusion syndrome (PRIS) is defined as acute bradycardia progressing to asystole combined with lipemic plasma, fatty liver enlargement, metabolic acidosis with negative base excess >10 mmol l(-1), rhabdomyolysis or myoglobinuria associated with propofol infusion. The purpose of this review was to provide a new update of reported case reports and to describe recent retrospective studies and animal research relevant for the pathophysiology and clinical presentation of PRIS. New case reports of PRIS have confirmed previously identified risk factors, and have also further revealed the incidence of PRIS in patients previously not estimated to be at risk for this syndrome. Retrospective studies contributed new evidence to the incidence of PRIS and development of PRIS even at propofol doses commonly used for surgical anesthesia. An animal study confirmed potential pathophysiological pathways and showed new organ manifestations possibly associated with propofol infusion. Further clinical and experimental evidence has confirmed the existence of PRIS as a rare but highly lethal complication of propofol use not limited to prolonged use of propofol. PRIS has to be kept in mind if propofol is used for anesthesia or sedation. Recommendations for the limitation of propofol use have to be adhered to. Early warning signs must prompt immediate cessation of propofol infusion and adequate treatment.

Vasopressin treatment of verapamil toxicity in the porcine model

INTRODUCTION

Vasopressin is a novel vasopressor agent used for intractable hypotension. There is little published data available on its use in the poisoned patient. We performed a randomized, controlled, blinded trial in a porcine model to study the effects of vasopressin infusion on mean arterial pressure after verapamil poisoning.

METHODS

Eighteen anesthetized monitored swine received a verapamil infusion of 1 mg/kg/hr until the mean arterial pressure (MAP) had decreased to 70% of baseline. At this time, a continuous infusion of either vasopressin (0.01 U/kg/min) or an equal volume of normal saline was initiated. The swine were monitored for 60 minutes after initiation of the study infusion. The primary outcome was MAP.

RESULTS

There was no statistically significant difference between the two groups in MAP, cardiac output or systemic vascular resistance. One half (four of eight) of the animals in the vasopressin group died, compared with 20% (two of ten) of those in the saline group.

CONCLUSIONS

Vasopressin infusion decreased the survival of verapamil-poisoned swine when compared to those treated with saline alone in this experimental model.

Pharmacokinetics of lidocaine with epinephrine following local anesthesia reversal with phentolamine mesylate

Phentolamine mesylate accelerates recovery from oral soft tissue anesthesia in patients who have received local anesthetic injections containing a vasoconstrictor. The proposed mechanism is that phentolamine, an alpha-adrenergic antagonist, blocks the vasoconstriction associated with the epinephrine used in dental anesthetic formulations, thus enhancing the systemic absorption of the local anesthetic from the injection site. Assessments of the pharmacokinetics of lidocaine and phentolamine, and the impact of phentolamine on the pharmacokinetics of lidocaine with epinephrine were performed to characterize this potentially valuable strategy. The blood levels of phentolamine were determined following its administration intraorally and intravenously. Additionally, the effects of phentolamine mesylate on the pharmacokinetics of intraoral injections of lidocaine with epinephrine were evaluated. Sixteen subjects were enrolled in this phase 1 trial, each receiving 4 drug treatments: 1 cartridge lidocaine/epinephrine followed after 30 minutes by 1 cartridge phentolamine (1L1P), 1 cartridge phentolamine administered intravenously (1Piv), 4 cartridges lidocaine/epinephrine followed after 30 minutes by 2 cartridges phentolamine (4L2P), and 4 cartridges lidocaine/epinephrine followed by no phentolamine (4L). Pharmacokinetic parameters estimated for phentolamine, lidocaine, and epinephrine included peak plasma concentration (Cmax), time to peak plasma concentration (Tmax), area under the plasma concentration-time curve from 0 to the last time point (AUClast) or from time 0 to infinity (AUCinf), elimination half-life (t1/2), clearance (CL), and volume of distribution (Vd). The phentolamine Tmax occurred earlier following the intravenous administration of 1Piv (7 minutes than following its submucosal administration in treatment 1L1P (15 minutes) or 4L2P (11 minutes). The phentolamine t1/2, CL, and Vd values were similar for 1L1P, 1Piv, and 4L2P. The Tmax for lidocaine occurred later and the Cmax for lidocaine was slightly higher when comparing the 4L2P treatment and the 4L treatment. The phentolamine-induced delay of the lidocaine Tmax likely represents phentolamine's ability to accelerate the systemic absorption of lidocaine from oral tissues into the systemic circulation.

Lighter General Anesthesia Causes Less Decrease in Arterial Pressure Induced by Epinephrine Scalp Infiltration During Neurosurgery

Scalp infiltration with epinephrine-containing lidocaine solution can elicit significant hypotension before craniotomy under general anesthesia. A prospective randomized controlled study was designed to observe whether a lighter depth of general anesthesia could prevent the unintentional hypotension induced by the epinephrine scalp infiltration during neurosurgery or not. Fifty patients undergoing scheduled neurosurgery involving craniotomy were randomly allocated into 2 groups. After anesthesia induction, anesthesia was maintained with propofol 2 mug/mL and rimifentanil 2 ng/mL by target-controlled infusion in group 1, and propofol 4 microg/mL and rimifentanil 4 ng/mL in group 2 (control group), respectively. All the patients received epinephrine scalp infiltration with 1% lidocaine 16 mL containing epinephrine 5 microg/mL. Mean arterial pressure (MAP) and heart rate were recorded at 30-second interval from the baseline to 5 minutes after the beginning of local infiltration. Bispectral index readings indicated group 1 had the lighter general anesthesia than group 2 (P<0.05). MAP was higher (P<0.05) and heart rate was lower (P<0.05) at 1.5 minutes time point in group 1 than group 2. The mean percentage of maximal decrease in MAP was group 1 (13%) <group 2 (24%) (P<0.05). The mean percentage of maximal increase in MAP was group 1 (10%)> group 2 (4%) without significant difference (P>0.05). The results implied that keeping a lighter general anesthesia caused less decrease in arterial blood pressure and was a relative effective method to prevent hypotension episode induced by epinephrine scalp infiltration.

A Unique Iontophoretic Patch for Optimal Transdermal Delivery of Sumatriptan

PURPOSE

Migraines affect approximately 10% of the adult population worldwide. The purpose of this study was to assess the pharmacokinetic and safety profile of a novel iontophoretic sumatriptan delivery system, NP101, which uses an electrical current to propel sumatriptan across intact skin and into underlying tissue. Four unique prototype iontophoretic sumatriptan patch conditions were compared to a 6 mg subcutaneous injection and an oral 50 mg tablet of sumatriptan succinate.

MATERIALS AND METHODS

This was a randomized, single-center, single-dose, six-period Phase I study.

RESULTS

Patches were well tolerated with fewer adverse events than the subcutaneous injection. Adverse events that were more prevalent for NP101 than other formulations included localized sensations and reactions at the patch site. A linear relationship was observed between total applied current and sumatriptan delivery. Patches delivering 6 and 12 mA per h yielded favorable sumatriptan systemic profiles, delivering drug at a rate that maintained plasma levels above the target level (> or = 10 ng/ml) for greater than 7 h.

CONCLUSIONS

This study met the initial objective to define the dose-current relationship in humans as well as delimiting specific current and current density targets for a well tolerated patch design that can deliver therapeutic drug levels for longer periods than currently possible.

Luteinising hormone attenuates the vascular response to norepinephrine

The present study examines the direct effect of luteinising hormone (LH) on the reactivity of the porcine uterine artery to norepinephrine (NE). Three-mm-long arterial segments collected during the luteal phase of the oestrous cycle were mounted in an organ bath for isometric tension recording. After 30 min of equilibration in optimal passive tone, one part of the vessels was treated with 10 ng/ml of LH in PBS (experimental), while a second part of the arterial segments was treated with 10 ng/ml of bovine serum albumin (BSA) in PBS (control). After 30 min of equilibration, NE was given to each organ bath in a cumulative concentration manner, ranging between 1 x 10(-8) mol/l to 3 x 10(-4) mol/l. NE caused a dose-dependent contraction of all experimental and control arteries. The addition of LH caused a rightward shift of the dose-response curve to NE. The corresponding EC50 values were 2.17 (+/- 0.39) micromol/l in PBS-pretreated vessels and 3.35 (+/- 0.41) micromol/l in LH-pretreated vessels (P < 0.05). The results of the present study demonstrate that LH attenuates the vascular response to NE in third-order branches of the uterine artery. Therefore, it can be suggested that besides the known effect of LH-hCG on the formation of vasoactive eicosanoids, an additional mechanism is involved in the direct action of LH on blood flow in the uterine arteries in pigs.

Nasal delivery of antimigraine drugs: clinical rationale and evidence base

The intranasal route of administration for antimigraine drugs offers many theoretical and practical advantages. A drug that is administered intranasally is absorbed by the highly vascular mucous membranes of the nose, which allows for rapid delivery of un-metabolized drug to the central nervous system. The onset of action is thus considerably earlier than with oral administration requiring gastrointestinal absorption. The intranasal route also provides several practical advantages, such as greater acceptability to patients because of the noninvasive mode of delivery, the ability to take medication when severe nausea or vomiting is present, and a better adverse event profile. Three antimigraine drugs are available in intranasal formulation: dihydroergotamine, sumatriptan, and zolmitriptan. This article reviews the pharmacology, efficacy, safety, and tolerability of these agents. All are well tolerated by patients and have demonstrated efficacy in the treatment of migraine headache. Each of these drugs has a unique pharmacokinetic and pharmacodynamic profile, which may support a clinical preference for one intranasal agent over another in treating patients with specific headache features.

Vasopressors for cardiopulmonary resuscitation. Does pharmacological evidence support clinical practice?

Adrenaline (epinephrine) has been used for cardiopulmonary resuscitation (CPR) since 1896. The rationale behind its use is thought to be its alpha-adrenoceptor-mediated peripheral vasoconstriction, causing residual blood flow to be diverted to coronary and cerebral circulations. This protects these tissues from ischaemic damage and increases the likelihood of restoration of spontaneous circulation. Clinical trials have not demonstrated any benefit of adrenaline over placebo as an agent for resuscitation. Adrenaline has deleterious effects in the setting of resuscitation, predictable from its promiscuous pharmacological profile. This article discusses the relevant pharmacology of adrenaline in the context of CPR. Experimental and clinical evidences for the use of adrenaline and alternative vasopressor agents in resuscitation are given, and the properties of an ideal vasopressor are discussed.

Endothelium-derived steroidogenic factor enhances angiotensin II-stimulated aldosterone release by bovine zona glomerulosa cells

Endothelium-derived steroidogenic factor (EDSF) is an endothelial peptide that stimulates aldosterone release from bovine adrenal zona glomerulosa (ZG) cells. The regulation of aldosterone release by combinations of EDSF and angiotensin II (AII) or EDSF and ACTH was investigated. Endothelial cells (ECs) and EC-conditioned media (ECCM) increased aldosterone release from ZG cells, an activity attributed to EDSF. AII (10(-12) to 10(-8) M) and ACTH (10(-12) to 10(-9) M) also stimulated the release of aldosterone from ZG cells. The stimulation by AII, but not ACTH, was greatly enhanced when ZG cells were coincubated with ECs. AII was metabolized by ECs to peptides identified by mass spectrometry as angiotensin (1-7) and angiotensin IV. There was very little metabolism of AII by ZG cells. Neither of these two AII metabolites altered aldosterone release from ZG cells, so they could not account for the enhanced response with ECs. AII-induced aldosterone release from ZG cells was enhanced by ECCM but not cell-free conditioned medium. This enhanced response was not due to increased EDSF release from ECs by AII. The synergistic effect of EDSF and AII was apparent when AII was added during or after the generation of ECCM and not observed when the AII component of the enhancement was blocked by the AII antagonist, losartan. These studies indicate that EDSF enhances the steroidogenic effect of AII. In the adrenal gland, ECs are in close anatomical relationship with ZG cells and may sensitize ZG cells to the steroidogenic action of AII by releasing EDSF.

Haemodynamic effects of adrenaline (epinephrine) depend on chest compression quality during cardiopulmonary resuscitation in pigs

BACKGROUND

Adrenaline (epinephrine) is used during cardiopulmonary resuscitation (CPR) based on animal experiments without supportive clinical data. Clinically CPR was reported recently to have much poorer quality than expected from international guidelines and what is generally done in laboratory experiments. We have studied the haemodynamic effects of adrenaline during CPR with good laboratory quality and with quality simulating clinical findings and the feasibility of monitoring these effects through VF waveform analysis.

METHODS AND RESULTS

After 4 min of cardiac arrest, followed by 4 min of basic life support, 14 pigs were randomised to ClinicalCPR (intermittent manual chest compressions, compression-to-ventilation ratio 15:2, compression depth 30-38 mm) or LabCPR (continuous mechanical chest compressions, 12 ventilations/min, compression depth 45 mm). Adrenaline 0.02 mg/kg was administered 30 s thereafter. Plasma adrenaline concentration peaked earlier with LabCPR than with ClinicalCPR, median (range), 90 (30, 150) versus 150 (90, 270) s (p = 0.007), respectively. Coronary perfusion pressure (CPP) and cortical cerebral blood flow (CCBF) increased and femoral blood flow (FBF) decreased after adrenaline during LabCPR (mean differences (95% CI) CPP 17 (6, 29) mmHg (p = 0.01), FBF -5.0 (-8.8, -1.2) ml min(-1) (p = 0.02) and median difference CCBF 12% of baseline (p = 0.04)). There were no significant effects during ClinicalCPR (mean differences (95% CI) CPP 4.7 (-3.2, 13) mmHg (p = 0.2), FBF -0.2 (-4.6, 4.2) ml min(-1)(p = 0.9) and CCBF 3.6 (-1.8, 9.0)% of baseline (p = 0.15)). Slope VF waveform analysis reflected changes in CPP.

CONCLUSION

Adrenaline improved haemodynamics during laboratory quality CPR in pigs, but not with quality simulating clinically reported CPR performance.

Bioadhesive monolayer film for the in vitro transdermal delivery of sumatriptan

The work presented here aims to develop a bioadhesive monolayer film containing sumatriptan as adjuvant for the treatment of headache pain in a severe migraine attack. Permeation experiments were performed from the films prepared and from the respective solution, to evaluate the relevant permeation parameters. The effect of the penetration enhancers Transcutol, 2-pyrrolidone, and polyethylene glycol 600 was evaluated. The results obtained show that Transcutol and 2-pyrrolidone decreased sumatriptan permeation from solution, whereas a modest increase was produced by polyethylene glycol 600. The enhancers produced the same effects when they were included in the film. Compared to solution, the film showed a higher sumatriptan flux in the early times of the experiment. When the film was applied in occlusive conditions the profiles were much higher, indicating the importance of patch drying. Concerning skin retention, the bioadhesive film produced a reduction of the amount of sumatriptan remaining in the skin, but this can be advantageous in the control of drug input, since it reduces the reservoir effect in the skin and allows for an immediate interruption of drug input when the patch is removed.

Pharmacokinetics of CPU0213, a novel endothelin receptor antagonist, after intravenous administration in mice

AIM

To determine the pharmacokinetics associated with acute toxic doses of CPU0213, a novel endothelin receptor antagonist in mice after a single intravenous administration.

METHODS

Concentrations in serum and the pharmacokinetic parameters of CPU0213 were assayed by high pressure liquid chromatography (HPLC) following a single intravenous bolus of CPU0213 at concentrations of 25, 50, and 100 mg/kg in mice. The intravenous acute toxicity of CPU0213 was also assessed in mice.

RESULTS

A simple, sensitive and selective HPLC method was developed for quantitative determination of CPU0213 in mouse serum. The concentration-time data conform to a 2-compartment model after iv administration of CPU0213 at concentrations of 25, 50, 100 mg/kg. The corresponding distribution half-lives (T1/2 alpha ) were 3.6, 4.2, 1.1 min and the elimination half-lives (T1/2beta) were 39.4, 70.3, 61.9 min. There was a linear increase in C0 proportional to dose, and the same as AUC(0-t) and AUC(0-infinity);. AUC(0-t) and AUC(0-infinity) were 4.511, 13.070, 23.666 g x min x L(-1 ) and 4.596, 13.679, 24.115 g x min x L(-1), respectively. The intravenous LD50 was 315.5 mg/kg.

CONCLUSION

First order rate pharmacokinetics were observed for CPU0213 within the range of doses used, and the acute toxicity of CPU0213 is mild.

Pharmacokinetics of sumatriptan in non-respondent and in adverse drug reaction reporting migraine patients

Sumatriptan is a selective agonist of 5HT1 (1B/1D) receptors, which has proved to be effective and safe for the acute treatment of migraine attacks. Nevertheless, its use by migraine sufferers is still limited and some patients consider adverse reactions related to sumatriptan, especially chest symptoms, unacceptable even if not serious. Moreover, in clinical trials, almost one third and one sixth of patients, respectively, fail to experience headache relief either after oral or after subcutaneous sumatriptan administration. Our aim was to verify whether differencies in sumatriptan pharmacokinetics could explain non–response and/or adverse drug reactions. Sumatriptan levels were determined by HPLC with electrochemical detection. Pharmacokinetic parameters were calculated using a computer program (PK Solutions 2.0; non compartmental Pharmacokinetics Data Analysis). After oral administration, sumatriptan is rapidly absorbed and sometimes displays multiple peaks of plasma concentration. This “multiple peaking” gives rise to considerable inter–subject variability in the time of reaching maximum plasma concentration. Pharmacokinetic parameters of sumatriptan, both after oral and subcutaneous administration, were similar in the three patient groups. Blood pressure and heart rate did not show any significant differences between groups. Pharmacokinetic parameters and bioavailability of sumatriptan did not seem to be correlated either to the lack of efficacy or the appearance of side effects. These results could depend on the limited number of patients studied.

Uncertainty Analysis in Pharmacokinetics and Pharmacodynamics: Application to Naratriptan

PURPOSE

The aim of the study was to predict pain relief of migraine in patients following naratriptan oral (tablet) administration by using uncertainty analysis. The analysis was based on phase I pharmacokinetic naratriptan data, sumatriptan pharmacodynamic data, and naratriptan preclinical (animal) potency information, together with general knowledge as to how migraine affects oral absorption.

METHODS

A previously developed pharmacokinetic (PK)/pharmacodynamic (PD) model for naratriptan disposition and effect was used. The uncertain parameters in the model, which were associated with absorption and scaling between first-in-class compound sumatriptan and naratriptan, were modeled using fuzzy sets theory. Global sensitivity analysis was then used to investigate the impact of each PK/PD parameter on the responses.

RESULTS

Acknowledging parametric uncertainty did not improve prediction of the probability of pain relief. Global sensitivity analysis demonstrated that predictions were heavily influenced by interindividual variability in pharmacodynamics, as the dose response relationship was relatively insensitive to the pharmacokinetics.

CONCLUSIONS

To predict the probability of pain relief following oral (tablet) administration of naratriptan, a simple dose response, instead of the PK/PD model, would have yielded very similar predictions. The naratriptan PK/PD model may be improved by either refining the PD model or better still by specifying the interindividual error by additional data collecting with an improved design.

Intravenous butyrylcholinesterase administration and plasma and brain levels of cocaine and metabolites in rats

Butyrylcholinesterase is a major cocaine-metabolizing enzyme in humans and other primates, catalyzing hydrolysis to ecgonine methylester. Increasing butyrylcholinesterase activity may be a treatment for cocaine addiction. We evaluated the effect of 30-min pretreatment with horse-derived butyrylcholinesterase (5-15,000 U i.v.) or with the selective butyrylcholinesterase inhibitor cymserine (10 mg/kg i.v.) on the metabolism of cocaine (17 mg/kg i.p.) in anesthetized rats. Venous blood samples were collected for two hours after cocaine administration and later assayed for cocaine and metabolites by gas chromatography/mass spectroscopy. Whole brains were collected after the last blood sample and similarly assayed. Butyrylcholinesterase significantly increased plasma and brain ecgonine methylester levels and decreased cocaine plasma half-life from 26.2 min (saline) to 16.4 min (15,000 U). Butyrylcholinesterase had no significant effect on plasma or brain cocaine or benzoylecgonine levels. Cymserine had no effect on any variable. These findings suggest that butyrylcholinesterase treatment may have benefits in enhancing cocaine metabolism and in increasing levels of ecgonine methylester, which may have a protective action against cocaine.

Glomerular permeability defect in hypertension is dependent on renin angiotensin system activation

BACKGROUND

The aim of the present study was to compare glomerular permeability alterations associated with experimental hypertension models known to have different effects on the circulating renin-angiotensin system (RAS).

METHODS

Five groups, 10 animals each, were studied. One group served as a nonhypertensive control. The other four groups of hypertensive animals were composed of spontaneously hypertensive rats, deoxycorticosterone acetate hypertensive rats, Goldblatt two-kidney, one-clip rats, and a group of Wistar rats infused with angiotensin II (200 ng/kg/min). Tail-cuff sphygmomanometric systolic blood pressure (BP), albumin permeability determined in isolated glomeruli exposed to oncotic gradients (P(alb)), glomerular filtration rate (GFR, iopamidol method), plasma renin activity (PRA), and albuminuria were evaluated.

RESULTS

Alterations in P(alb) and albumin excretion rate were more evident in the experimental models with an activation of the RAS despite similar levels of systolic BP and GFR. A positive correlation was found between P(alb) and albuminuria (r = 0.51; P < .001) and between systolic BP and albuminuria (r = 0.37; P < .01). No relation was found between systolic BP and P(alb).

CONCLUSIONS

The present study indicates that the activation of the RAS plays a significant role in the development of glomerular albumin permeability defects in hypertensive models and may contribute to the mechanisms that lead to target organ damage in hypertension.

Effects of a fast disintegrating/rapid release oral formulation of sumatriptan on functional ability in patients with migraine

BACKGROUND

A new oral form of sumatriptan has been developed to facilitate tablet disintegration and drug dispersion and to mitigate the effects of gastric stasis that can accompany migraine.

OBJECTIVE

To evaluate the effects on functional ability of the new fast disintegrating/rapid release formulation of sumatriptan.

METHODS

Sumatriptan 50 mg (n = 137), 100 mg (n = 142), or placebo (n = 153) was administered early when pain was mild for the acute treatment of a single migraine attack in a randomized, double-blind, parallel-group, placebo-controlled clinical trial. For this report, main health-outcomes endpoints (which were secondary endpoints for this clinical trial that was primarily designed to assess pain-free efficacy) included functional ability measured through 2 h postdose on a 5-point scale and lost time equivalents, a composite measure of migraine-associated time missed from activities, and reduced effectiveness at activities through 24 h postdose.

RESULTS

Normal functional ability was restored in a significantly (p < 0.05) greater percentage of patients treated with sumatriptan than placebo beginning 45 min postdose for sumatriptan 100 mg and 1 h postdose for sumatriptan 50 mg. During the 24 h after initial dosing, the median (range) lost time equivalents for the combination of paid work activities and activities outside of paid work were significantly lower in the groups treated with sumatriptan (1.1 [0-10] sumatriptan 100 mg; 0.8 [0-36] sumatriptan 50 mg) compared with placebo (2.9 [0-24]) (p < or = 0.01 each sumatriptan group versus placebo). The corresponding mean +/- SD values for lost time equivalents were 1.9 +/- 2.3 and 2.5 +/- 4.7 for sumatriptan 100 mg and 50 mg, respectively, compared with 3.5 +/- 4.3 for placebo.

CONCLUSION

A new oral sumatriptan formulation confers rapid, sustained restoration of functional ability in the acute treatment of migraine so that patients can return rapidly to normal functioning at work and outside of work.

Pharmacokinetics and Safety of Epinephrine Use in Liposuction

Patients are routinely exposed to high-dose epinephrine infiltration during large-volume liposuction. Because of the serious cardiovascular side-effect profile of catecholamine overdose, the authors examined the safety of larger-volume liposuction by assessing epinephrine pharmacokinetics. Five female volunteers with American Society of Anesthesiologists physical status of I or II, aged 29 to 40 years and weighing 75.9 to 95 kg, underwent liposuction. The wetting solution contained 7.3 mg (SEM, 0.7 mg) of epinephrine, corresponding to 0.09 mg/kg (0.04 mg/kg). Total plasma epinephrine and norepinephrine concentrations were assessed by high-performance liquid chromatography. Approximate exogenous epinephrine absorption was calculated after correction for estimated endogenous epinephrine production. Pharmacokinetic assessments were performed using standard equations. The total plasma epinephrine peak occurred at the final intraoperative reading (5 hours after induction) and was 323 pg/ml (24.8 pg/ml), three to four times maximum baseline resting levels. The norepinephrine level was slightly elevated throughout the study period, with a reversal of the normal epinephrine/norepinephrine ratio (<0.5:1) demonstrated intraoperatively (>5:1). Estimated time to peak exogenous epinephrine level ranged from 1 to 4 hours from the start of infiltration. Area under the plasma concentration versus time curve was approximately 2089 to 2610 pg x hour/ml. Peak exogenous epinephrine concentration was estimated to be 286 to 335 pg/ml. Clearance was 764,508 ml/hour and volume of distribution was 0.4 liter/kg (0.006 liter/kg). Total absorbed epinephrine was estimated, 1.8 mg to 2.2 mg, equivalent to 25 to 32 percent of the infiltrated dose. The reversal of the normal epinephrine/norepinephrine ratio and the fact that norepinephrine levels were within normal range implied that the majority of plasma epinephrine measured was exogenously infiltrated and not endogenously synthesized. On the basis of these observations, pharmacokinetic analyses were performed. Although unequivocal toxic epinephrine levels were not demonstrated, epinephrine peaks were three to four times the maximum observed in normal resting patients. Peak levels were comparable to those observed during major physiologic stresses, such as exercising to exhaustion, open abdominal surgery, or cross-clamping the aorta during surgical repair. Furthermore, epinephrine has been associated with myocardial infarction, arrhythmias, and fatal asystole in susceptible patients at these levels. Patients should be carefully screened for clinical evidence of hemodynamic and cardiac pathology before larger-volume liposuction is undertaken, as it may result in unnecessary high risk for patients who have preexisting cardiovascular disorders. Healthy American Society of Anesthesiologists physical status I or II patients should have sufficient cardiac reserve to tolerate these catecholamine levels.

Angiotensin II type 1 receptor-mediated augmentation of renal interstitial fluid angiotensin II in angiotensin II-induced hypertension

BACKGROUND

Angiotensin II (Ang II)-dependent hypertension is associated with augmented intrarenal concentrations of Ang II; however, the distribution of the increased intrarenal Ang II has not been fully established.

OBJECTIVE

To determine the changes in renal interstitial fluid Ang II concentrations in Ang II-induced hypertension and the consequences of treatment with an angiotensin II type 1 (AT1) receptor blocker.

DESIGN AND METHODS

Rats were selected to receive vehicle (5% acetic acid subcutaneously; n = 6), Ang II (80 ng/min subcutaneously, via osmotic minipump; n = 7) or Ang II plus an AT1 receptor antagonist, candesartan cilexetil (10 mg/kg per day, in drinking water; n = 6) for 13-14 days, at which time, experiments were performed on anesthetized rats. Microdialysis probes were implanted in the renal cortex and were perfused at 2 microl/min. The effluent dialysate concentrations of Ang I and Ang II were measured by radioimmunoassay and reported values were corrected for the equilibrium rates at this perfusion rate.

RESULTS

Ang II-infused rats developed greater mean arterial pressures (155 +/- 7 mmHg) than vehicle-infused rats (108 +/- 3 mmHg). Ang II-infused rats showed greater plasma (181 +/- 30 fmol/ml) and kidney (330 +/- 38 fmol/g) Ang II concentrations than vehicle-infused rats (98 +/- 14 fmol/ml and 157 +/- 22 fmol/g, respectively). Renal interstitial fluid Ang II concentrations were much greater than plasma concentrations, averaging 5.74 +/- 0.26 pmol/ml in Ang II-infused rats - significantly greater than those in vehicle-infused rats (2.86 +/- 0.23 pmol/ml). Candesartan treatment prevented the hypertension (87 +/- 3 mmHg) and led to increased plasma Ang II concentrations (441 +/- 27 fmol/ml), but prevented increases in kidney (120 +/- 15 fmol/g) and renal interstitial fluid (2.15 +/- 0.12 pmol/ml) Ang II concentrations.

CONCLUSIONS

These data indicate that Ang II-infused rats develop increased renal interstitial fluid concentrations of Ang II, which may contribute to the increased vascular resistance and reduced sodium excretion. Furthermore, the augmentation of renal interstitial fluid Ang II is the result of an AT1 receptor-mediated process and can be dissociated from the plasma concentrations.

Zolmitriptan nasal spray: advances in migraine treatment

Zolmitriptan nasal spray was developed specifically to achieve fast, high effectiveness and to overcome many of the limitations associated with oral and sc migraine therapies. Pharmacokinetic studies have demonstrated a very rapid appearance of zolmitriptan in plasma as early as 5 minutes after intranasal dosing, with about 40% of peak plasma concentration (C(max)) being achieved within 10 to 15 minutes of dosing. Comparison of plasma concentration-time profiles of zolmitriptan and its active metabolite after oral and intranasal administration, together with PET scanning, clearly indicate direct absorption of zolmitriptan across the nasal mucosa after intranasal administration. The remainder of the dose is then swallowed and is absorbed through the gastrointestinal tract. In one blinded, randomized, placebo-controlled, multiple-attack study of zolmitriptan nasal spray, headache response was superior to placebo as early as 15 minutes after dosing (p < 0.05). In the zolmitriptan 5 mg treatment group, the primary end point of 2-hour headache response was achieved in 70% (300/427) of attacks versus 31% of attacks (119/389 attacks) in the placebo group (p < 0.001). Patients achieved a 2-hour headache response, had no recurrence, and used no additional or escape medications for up to 24 hours in 49% of attacks versus 14% of attacks in the placebo group (p < 0.001). Zolmitriptan 5 mg nasal spray was well tolerated. These data and those from other similar studies demonstrate that zolmitriptan nasal spray combines early, sustained efficacy and good tolerability, making it an optimal acute treatment for migraine.

[The renin-angiotensin system in human brain and brain tumors: a function unrelated to blood pressure control?]

The renin-angiotensin system (RAS), in addition to controlling blood pressure and the sodium-water balance, may be involved in cell growth and/or death in the brain. In order to address this issue, we compared the expression of RAS components in surgical specimens of human brain tumors and adjacent tissue. Human brain tumor cells and rat brain cells in culture were used to evaluate RAS functions. We found evidence that the RAS may be involved in maintaining the functions of the cerebral vasculature (the blood-brain-barrier) by controlling the ratio between angiotensin II and angiotensin III production, and by playing a more direct role in the survival of astroglial cells.

Pharmacokinetics and pharmacodynamics of dopamine and norepinephrine in critically ill head-injured patients

OBJECTIVE

To explore the pharmacokinetics and pharmacodynamics of dopamine and norepinephrine.

DESIGN

Prospective, controlled, trial.

SETTING

Neurosciences critical care unit.

PATIENTS

Eight patients with a head injury, requiring dopamine or norepinephrine infusions to support cerebral perfusion pressure (CPP).

INTERVENTION

Patients received in randomised order, either dopamine or norepinephrine to achieve and maintain a CPP of 70 mmHg, and then, following a 30-min period of stable haemodynamics, a CPP of 90 mmHg. Data were then acquired using the second agent. Haemodynamic measurements were made during each period and a blood sample was obtained at the end of each study period for analysis of plasma catecholamine concentrations

MEASUREMENTS AND RESULTS

Plasma levels of norepinephrine and dopamine were significantly related to infusion rates but did not have a simple linear relationship to haemodynamic parameters. However, there was a significant quadratic relationship between the infusion rate of dopamine and cardiac index (r2=0.431), and systemic vascular resistance index (r2=0.605), with a breakpoint (at which cardiac index reduced and SVRI increased) at a dopamine plasma level of approximately 50 nM/l (corresponding to an infusion rate of approximately 15 microg.kg(-1).min(-1)).

CONCLUSIONS

Norepinephrine and dopamine have predictable pharmacokinetics; however, those of dopamine do not fit a simple first-order kinetic model. The pharmacodynamic effects of dopamine and norepinephrine show much inter-individual variability and unpredictability. Plasma levels of dopamine appear to relate to variations in adrenergic receptor effects with break points that reflect expectations from infusion-rate related pharmacodynamics.

Evaluation of the blood-brain barrier transport, population pharmacokinetics, and brain distribution of benztropine analogs and cocaine using in vitro and in vivo techniques

The N-substituted 3alpha-[bis(4'-fluorophenyl)methoxy]tropanes (AHN 2-003, AHN 1-055, AHN 2-005, and JHW 007) bind with high affinity to the dopamine transporter and inhibit dopamine uptake more potently than cocaine, but they demonstrate behavioral profiles in animal models of psychostimulant abuse that are unlike that of cocaine. The objective of this study was to characterize the in vitro permeability, brain distribution, and pharmacokinetics of the benztropine (BZT) analogs. Transport studies of cocaine and the BZT analogs (10-4 M) were conducted across bovine brain microvessel endothelial cells. Male Sprague-Dawley rats (approximately 300 g) were administered BZT analogs (10 mg/kg) or cocaine (5 mg/kg) via the tail vein. Blood and brain samples were collected over 36 h and assayed using UV-high-performance liquid chromatography. Transport of both AHN 1-055 (2.15 x 10-4 cm/s) and JHW 007 (2.83 x 10-4 cm/s) was higher (p < 0.05) than that of cocaine (1.63 x 10-4 cm/s). The volume of distribution (12.3-30.5 l/kg) of the analogs was significantly higher than cocaine (0.9 l/kg). The BZT analogs displayed a > or =8-fold higher elimination half-life (4.12-16.49 h) compared with cocaine (0.49 h). The brain-to-plasma partition coefficients were at least two-fold higher for the BZTs versus cocaine, except for AHN 2-003. The BZT analogs are highly permeable across the blood-brain barrier and possess a pharmacokinetic profile different from that of cocaine. These characteristics, in addition to their distinctive behavioral profiles, suggest that the BZT analogs may be promising candidates for the treatment of cocaine abuse.

Effects of different angiotensins during acute, double blockade of the renin system in conscious dogs

Evidence of biological activity of fragments of ANG II is accumulating. Fragments considered being inactive degradation products might mediate actions previously attributed to ANG II. The study aimed to determine whether angiotensin fragments exert biological activity when administered in amounts equimolar to physiological doses of ANG II. Cardiovascular, endocrine, and renal effects of ANG II, ANG III, ANG IV, and ANG-(1-7) (6 pmol.kg-1.min-1) were investigated in conscious dogs during acute inhibition of angiotensin I-converting enzyme (enalaprilate) and aldosterone (canrenoate). Furthermore, ANG III was investigated by step-up infusion (30 and 150 pmol.kg-1.min-1). Arterial plasma concentrations [ANG immunoreactivity (IR)] were determined by an ANG II antibody cross-reacting with ANG III and ANG IV. Metabolic clearance rates were higher for ANG III and ANG IV (391 +/- 19 and 274 +/- 13 ml.kg-1.min-1, respectively) than for ANG II (107 +/- 13 ml.kg-1.min-1). ANG II increased ANG IR by 60 +/- 7 pmol/ml, blood pressure by 30%, increased plasma aldosterone markedly (to 345 +/- 72 pg/ml), and plasma vasopressin transiently, while reducing glomerular filtration rate (40 +/- 2 to 33 +/- 2 ml/min), sodium excretion (50 +/- 7 to 16 +/- 4 micromol/min), and urine flow. Equimolar amounts of ANG III induced similar antinatriuresis (57 +/- 8 to 19 +/- 3 micromol/min) and aldosterone secretion (to 268 +/- 71 pg/ml) at much lower ANG IR increments ( approximately 1/7) without affecting blood pressure, vasopressin, or glomerular filtration rate. The effects of ANG III exhibited complex dose-response relations. ANG IV and ANG-(1-7) were ineffective. It is concluded that 1) plasma clearances of ANG III and ANG IV are higher than those of ANG II; 2) ANG III is more potent than ANG II in eliciting immediate sodium and potassium retention, as well as aldosterone secretion, particularly at low concentrations; and 3) the complexity of the ANG III dose-response relationships provides indirect evidence that several effector mechanisms are involved.

Clinical applications of new therapeutic deliveries in migraine

A number of serotonin (5-HT)1B/1D agonists (triptans) are available worldwide for the treatment of migraine. The first-generation triptan, sumatriptan, was initially launched as an SC injection, which is fast-acting and consistently effective but relatively expensive and can be associated with adverse events in some patients. Sumatriptan was then launched as an oral tablet, shortly followed by the development of second-generation triptans that are now available in several formulations. Tablets are highly effective and convenient but may not be suitable in all migraine situations, e.g., migraine-associated nausea or vomiting and gastric disturbances. An intranasal route of administration appears to be an obvious way to deliver a migraine treatment and two triptans, sumatriptan and zolmitriptan, are available in nasal spray formulations. Sumatriptan offered the first nasal spray and has similar efficacy to the sumatriptan tablet, but the response is inconsistent and many patients cannot tolerate the unpleasant taste. The latest nasal spray, zolmitriptan, has produced exciting results in clinical studies and combines a rapid onset of action and consistently high response rates with a good tolerability profile. Early results from the author's clinic suggest that this promise is realized in clinical practice and that this combination of patient benefits makes zolmitriptan nasal spray an ideal way for patients to treat their migraine. With the introduction of zolmitriptan nasal spray, zolmitriptan is now available in three different formulations, enabling patients to tailor their treatment to the circumstances of the individual attack.

Effects of the prilocaine and of the association of prilocaine with different vasoconstrictors on the isolated hearts of rats

This study aimed to observe the effects of prilocaine chloridate (P) and the associations of P with felypressin (P+F), and epinephrine (P+E) on the heart rate and force of contraction on the isolated hearts of rats. The hearts were perfused according to Langendorff's method. The experiments were performed with the following substances: prilocaine (P), felypressin (F), and epinephrine (E). P was used in doses of 1.25, 2.5, and 5.0 mg. The same doses of F and P (1.0, 1.5 and 3.0 microg) were used in association with the P, respectively. Right after the application of the three doses of P, a reduction in the force of contraction was observed, with higher intensity at a higher dose, which led to cardiac arrest. A similar result was obtained with the administration of the three associations of P+F. Also the application of the three associations P+E resulted in a reduction of the force of contraction, that was, however, less intense with the associations of 1.25 mg P + 1.0 microg E and 2.5 mg P+1.5 microg E, as compared to the same doses of P alone and P+F. The two higher doses of P and P+F on the heart rate elicited a significant reduction in relation to the control, but with the associations of P+E no alterations were observed, with any one of the doses used. The results obtained in the present study suggest that an association of P and E must be used in local anesthesia, since epinephrine may well protect the heart from the depressive effects of the anesthetic salts.

Dose-Dependent Actions and Temporal Effects of Angiotensin II on Microvascular Permeability

BACKGROUND

Angiotensin II is a potent vasoconstrictor that is elevated after shock. Previous studies suggest that angiotensin II may directly modulate the endothelial barrier. Our hypothesis was that angiotensin II would increase microvascular hydraulic permeability in a dose-dependent fashion.

METHODS

Hydraulic permeability (Lp) is a measure of water flow across the endothelial barrier. Lp was measured in rat mesenteric venules using the modified Landis micro-occlusion technique. Venules were first perfused with Ringer's solution and baseline measurements of Lp were obtained. The venules were then recannulated and perfused with angiotensin II at 0.2 ng/mL (n = 5), 2.0 ng/mL (n = 5), 20 ng/mL (n = 8), and 200 ng/mL (n = 5), before final Lp measurements.

RESULTS

Baseline values for Lp averaged 1.35 +/- 0.12. The 20-ng/mL and 200-ng/mL concentrations of angiotensin II significantly increased Lp to 3.86 +/- 0.4 (p < 0.0008) and 7.94 +/- 1.1 (p < 0.005), respectively. The maximal effect of angiotensin II was seen at 15 minutes of perfusion. Units for Lp are x 10(-7) cm.s-1.cm H2O-1.

CONCLUSION

Angiotensin II affects a dose-dependent increase in microvascular permeability. This suggests that angiotensin II is involved in modulating intravascular fluid flux across the vessel wall. This effect is opposite to that observed in other vasoconstrictors that are up-regulated after trauma.

Neurovascular dissociation with paradoxical forearm vasodilation during systemic tyramine administration

BACKGROUND

Despite the widespread use of tyramine as a pharmacological tool to assess the effects of norepinephrine release from sympathetic nerve terminals, its vascular effects are not adequately characterized. In particular, previous results indicate that intravenous tyramine produces little if any systemic vasoconstriction, suggesting that tyramine does not cause significant norepinephrine release from sympathetic nerves innervating peripheral vascular beds. To test this hypothesis, we determined the effects of intravenous tyramine on local forearm norepinephrine spillover and vascular resistance.

METHODS AND RESULTS

Seven healthy subjects were studied with systemic and local forearm norepinephrine spillover and forearm blood flow at baseline, during systemic tyramine infusion, and after sympathetic stimulation induced by the cold pressor test. Tyramine infusion caused a significant increase in systemic and forearm norepinephrine spillover. The amount of norepinephrine released into the forearm by tyramine was similar to that caused by cold pressor stimulation, 0.15+/-0.05 versus 0.18+/-0.05 ng x dL(-1) x min(-1). As expected, forearm vascular resistance increased during the cold pressor test, but tyramine produced forearm vasodilation (4.5+/-1 versus -5+/-1 mm Hg x dL(-1) x min(-1), P<0.03) despite the increase in local norepinephrine spillover. In 6 additional subjects, plasma dopamine increased significantly during tyramine administration, from 11+/-3 to 662+/-105 pg/mL.

CONCLUSIONS

Thus, systemic tyramine infusion evokes a significant increase in peripheral norepinephrine spillover, and this, paradoxically, is associated with local vasodilatation rather than vasoconstriction.

Management of vasodilatory shock: defining the role of arginine vasopressin

The rationale for an arginine vasopressin (argipressin) infusion was put forward after it was discovered that patients in shock states might have an endogenous arginine vasopressin deficiency. Subsequently, several investigations impressively demonstrated that arginine vasopressin can successfully stabilise haemodynamics even in advanced vasodilatory shock. We report on physiological and pharmacological aspects of arginine vasopressin, and summarise current clinical knowledge on employing a continuous arginine vasopressin infusion in critically ill patients with catecholamine-resistant vasodilatory shock of different aetiologies. In view of presented experimental evidence and current clinical experience, a continuous arginine vasopressin infusion of approximately 2 to approximately 6 IU/h can be considered as a supplemental strategy to vasopressor catecholamines in order to preserve cardiocirculatory homeostasis in patients with advanced vasodilatory shock. Because data on adverse effects are still limited, arginine vasopressin should be reserved for patients in whom adequate haemodynamic stabilisation cannot be achieved with conventional vasopressor therapy or who have obvious adverse effects of catecholamines that result in further significant haemodynamic deterioration. For the same reasons, arginine vasopressin should not be used as a single, alternative vasopressor agent instead of catecholamine vasopressors. Future prospective studies will be necessary to define the exact role of arginine vasopressin in the therapy of vasodilatory shock.

Transdermal penetration of vasoconstrictors--present understanding and assessment of the human epidermal flux and retention of free bases and ion-pairs

PURPOSE

As reductions in dermal clearance increase the residence time of solutes in the skin and underlying tissues we compared the topical penetration of potentially useful vasoconstrictors (VCs) through human epidermis as both free bases and ion-pairs with salicylic acid (SA).

METHODS

We determined the in vitro epidermal flux of ephedrine, naphazoline, oxymetazoline, phenylephrine, and xylometazoline applied as saturated solutions in propylene glycol:water (1:1) and of ephedrine, naphazoline and tetrahydrozoline as 10% solutions of 1:1 molar ratio ion-pairs with SA in liquid paraffin.

RESULTS

As free bases, ephedrine had the highest maximal flux, Jmax = 77.4 +/- 11.7 microg/cm2/h, being 4-fold higher than tetrahydrozoline and xylometazoline, 6-fold higher than phenylephrine, 10-fold higher than naphazoline and 100-fold higher than oxymetazoline. Stepwise regression of solute physicochemical properties identified melting point as the most significant predictor of flux. As ion-pairs with SA, ephedrine and naphazoline had similar fluxes (11.5 +/- 2.3 and 12.0 +/- 1.6 microg/cm2/h respectively), whereas tetrahydrozoline was approximately 3-fold slower. Corresponding fluxes of SA from the ion-pairs were 18.6 +/- 0.6, 7.8+/- 0.8 and 1.1 +/- 0.1 respectively. Transdermal transport of VC's is discussed.

CONCLUSIONS

Epidermal retention of VCs and SA did not correspond to their molar ratio on application and confirmed that following partitioning into the stratum corneum, ion-pairs separate and further penetration is governed by individual solute characteristics.

Sumatriptan nasal spray for migraine: a review of studies in patients aged 17 years and younger

This review considers the epidemiology, clinical manifestations and functional consequences of migraine in children and adolescents and surveys the studies establishing the efficacy and tolerability of sumatriptan nasal spray in this patient population. Although therapeutic advances in paediatric and adolescent migraine have lagged behind those in adult migraine, the first systematic studies of migraine medications in young patients have brought about progress in the past five years. These studies show that therapeutic approaches suitable for adult patients are not always applicable to paediatric and adolescent patients. Because of the unique characteristics of paediatric and adolescent migraine, it has been difficult to demonstrate in young patients the efficacy of oral sumatriptan and other triptan tablets, which are the medications of choice for adult migraine. With sumatriptan, this finding has proven to be a consequence of the form in which the drug was administered rather than the inherent properties of the drug. The availability of sumatriptan nasal spray allows the benefits of migraine-specific therapy to be extended to children and adolescents. In both well-controlled, single-episode studies and long-term, multiple-episode studies, sumatriptan nasal spray has been effective and well tolerated for the acute treatment of migraine in children and adolescents. Except for unpleasant taste, which is not significantly distressing to patients, sumatriptan nasal spray has a tolerability profile similar to thatof placebo in young patients.