Polyinosinic acid and polycationic liposomes attenuate the hepatic clearance of circulating plasmid DNA

DNA that enters the circulation is rapidly cleared both by tissue uptake and by DNase-mediated degradation. In this study, we have examined the uptake of linear plasmid DNA in an isolated perfused liver model and following intra-arterial administration to rats. We found that the DNA was rapidly taken up by the isolated perfused liver without degradation. The single-pass extraction ratio was 0.76 +/- 0.05, the mean transit time was 15.3 +/- 3.6 s, and the volume of distribution was 0.29 +/- 0.07 ml/g. Hepatic uptake was saturable and was inhibited by polyinosinic acid or polycationic liposomes but not by condensation of the DNA with polylysine. When the linear plasmid DNA was administered in vivo, plasma half-life was 3.1 +/- 0.2 min, volume of distribution was 670 +/- 85 ml/kg, and clearance was 32 +/- 4 min. Coadministration of cationic liposomes decreased the volume of distribution to 180 +/- 28 ml/kg as well as the half-life (2.6 +/- 0.2 min). By contrast, polyinosinic acid significantly increased the circulating half-life (7.7 +/- 0.5 min), decreased the volume of distribution (95 +/- 17 ml/kg), and partially inhibited DNA degradation. When administered along with the liposomes and the polyinosinic acid, the distribution of plasmid-derived radioactivity decreased in the liver and increased in most other peripheral tissues. This study shows that pharmacological manipulation of the uptake and degradation of DNA can alter its distribution and clearance in vivo. These results may be useful in optimizing gene delivery procedures for in vivo gene therapy.

Diffusion- and perfusion-weighted MRI response to thrombolysis in stroke

Diffusion- and perfusion-weighted magnetic resonance imaging provides important pathophysiological information in acute bra-in ischemia. We performed a prospective study in 19 sub-6-hour stroke patients using serial diffusion- and perfusion-weighted imaging before intravenous thrombolysis, with repeat studies, both subacutely and at outcome. For comparison of ischemic lesion evolution and clinical outcome, we used a historical control group of 21 sub-6-hour ischemic stroke patients studied serially with diffusion- and perfusion-weighted imaging. The two groups were well matched for the baseline National Institutes of Health Stroke Scale and magnetic resonance parameters. Perfusion-weighted imaging-diffusion-weighted imaging mismatch was present in 16 of 19 patients treated with tissue plasminogen activator, and 16 of 21 controls. Perfusion-weighted imaging-diffusion-weighted imaging mismatch patients treated with tissue plaminogen activator had higher recanalization rates and enhanced reperfusion at day 3 (81% vs 47% in controls), and a greater proportion of severely hypoperfused acute mismatch tissue not progressing to infarction (82% vs -25% in controls). Despite similar baseline diffusion-weighted imaging lesions, infarct expansion was less in the recombinant tissue plaminogen activator group (14cm(3) vs 56cm(3) in controls). The positive effect of thrombolysis on lesion growth in mismatch patients translated into a greater improvement in baseline to outcome National Institutes of Health Stroke Scale in the group treated with recombinant tissue plaminogen activator, and a significantly larger proportion of patients treated with recombinant tissue plaminogen activator having a clinically meaningful improvement in National Institutes of Health Stroke Scale of;2:7 points. The natural evolution of acute perfusion-weighted imaging-diffusion-weighted imaging mismatch tissue may be altered by thrombolysis, with improved stroke outcome. This has implications for the use of diffusion- and perfusion-weighted imaging in selecting and monitoring patients for thrombolytic therapy.

Methadone maintenance therapy for opioid dependence - A guide to appropriate use

Opioid dependence is a chronic, relapsing condition that is associated with significant morbidity and mortality. Methadone maintenance therapy involves the provision of a controlled supply of an orally administered opioid, thereby stabilising the opioid-dependent patient. Research studies have shown that methadone maintenance reduces illicit opioid use, opioid-related crime, premature mortality and the risk of HIV infection. It is most effective when prescribed at an adequate dosage (usually 60 to 100 mg/day) and when long term maintenance on methadone is the goal of treatment rather than detoxification from all drugs including methadone. Successful long term methadone maintenance is more likely when it takes place within the context of a well established therapeutic relationship and when the medical, social and psychological needs of patients are met either through direct assistance or referral.

The distribution of naloxone to heroin users

Overdose deaths are a manor contributor to excess mortality among heroin users. It has been proposed that opioid overdose morbidity and mortality could be reduced substantially by distributing the opioid antagonist naloxone to heroin users. The ethical issues raised by this proposal are evaluated from a utilitarian perspective. The potential advantages of naloxone distribution include the increased chance of comatose opioid users being quickly resuscitated by others present at the time of an overdose, naloxone's safety and its lack of abuse potential. The main problems raised by the proposal are: the medico-legal complications of medical practitioners prescribing a drug that is most likely to be administered to and by people other than the one for whom it is prescribed; the economic costs of distributing naloxone sufficiently widely to have an impact on overdose morbidity and mortality; and the potentially greater cost-effectiveness of simpler educational interventions. Given the possible benefits of naloxone distribution, it may be worthwhile considering a controlled trial of naloxone distribution to high-risk heroin users.

Transdermal Pharmacology of Small Molecule Cyclic C5a Antagonists

Overproduction or underregulation of the proinflammatory complement component C5a has been implicated in numerous immune and inflammatory conditions. Therefore, targeting the C5a receptor (C5aR) has become an innovative strategy for antiinflammatory drug development. The novel cyclic peptide C5aR antagonist, AcF-[OP(D-Cha)WR] (PMX53), attenuates injury in numerous animal models of inflammation following intravenous, subcutaneous, intraperitoneal, and oral administration. In the present study the transdermal pharmacology of PMX53 and three analogs designed with increased lipophilicity, hydrocinnamate-[OP(D-Cha)WCit] (PMX200), AcF-[OP(D-Cha)WCit] (PMX201) and hydrocinnamate-[OP(D-Cha)WR] (PMX205), have been examined in order to assess their transdermal permeability and inhibitory effect on C5a-mediated lipopolysaccharide (LPS)-induced systemic responses. In the rat, PMX53, PMX201, and PMX205, were bioavailable following topical dermal administration (10 mg/50 cm(2) site/rat). All analogs functionally antagonized neutropenia and hypotension induced by systemic challenge with LPS (I mg/kg i.v.). Interestingly, PMX200 attenuated LPS-induced neutropenia more effectively than other analogs, despite undetectable (< 5 ng/ml) circulating levels following topical administration. In conclusion, we have demonstrated that cyclic peptide C5aR antagonists can penetrate transdermally sufficiently to have systemic effects. However, increasing lipophilicity in these compounds did not result in increased blood levels. Nonetheless, topical application of C5aR antagonists produced circulating levels of the drugs that antagonized the LPS-induced systemic responses of neutropenia and hypotension. This suggests that these small-molecule C5aR antagonists may be developed for topical administration for the treatment of local and systemic inflammatory conditions in the human and veterinary pharmaceutical markets.

Neurology of ciguatera

Ciguatera is a widespread ichthyosarcotoxaemia with dramatic and clinically important neurological features. This severe form of fish poisoning may present with either acute or chronic intoxication syndromes and constitutes a global health problem. Ciguatera poisoning is little known in temperate countries as a potentially global problem associated with human ingestion of large carnivorous fish that harbour the bioaccumulated ciguatoxins of the photosynthetic dinoflagellate Gambierdiscus toxicus. This neurotoxin is stored in the viscera of fish that have eaten the dinoflagellate and concentrated it upwards throughout the food chain towards progressively larger species, including humans. Ciguatoxin accumulates in all fish tissues, especially the liver and viscera, of at risk species. Both Pacific (P-CTX-1) and Caribbean (C-CTX-1) ciguatoxins are heat stable polyether toxins and pose a health risk at concentrations above 0.1 ppb. The presenting signs of ciguatera are primarily neurotoxic in more than 80% of cases. Such include the pathognomonic features of postingestion paraesthesiae, dysaesthesiae, and heightened nociperception. Other sensory abnormalities include the subjective features of metallic taste, pruritis, arthralgia, myalgia, and dental pain. Cerebellar dysfunction, sometimes diphasic, and weakness due to both neuropathy and polymyositis may be encountered. Autonomic dysfunction leads to hypotension, bradycardia, and hypersalivation in severe cases. Ciguatoxins are potent, lipophilic sodium channel activator toxins which bind to the voltage sensitive (site 5) sodium channel on the cell membranes of all excitable tissues. Treatment depends on early diagnosis and the early administration of intravenous mannitol. The early identification of the neurological features in sentinel patients has the potential to reduce the number of secondary cases in cluster outbreaks.

An identifiability analysis of a parent-metabolite pharmacokinetic model for ivabradine.

The paper considers the structural identifiability of a parent–metabolite pharmacokinetic model for ivabradine and one of its metabolites. The model, which is linear, is considered initially for intravenous administration of ivabradine, and then for a combined intravenous and oral administration. In both cases, the model is shown to be unidentifiable. Simplification of the model (for both forms of administration) to that proposed by Duffull et al. (1) results in a globally structurally identifiable model. The analysis could be applied to the modeling of any drug undergoing first-pass metabolism, with plasma concentrations available from drug and metabolite.

Human Fatalities from Cyanobacteria: Chemical and Biological Evidence for Cyanotoxins

An outbreak of acute liver failure occurred at a dialysis center in Caruaru, Brazil (8 degrees 17 'S, 35 degrees 58 'W), 134 km from Recife, the state capital of Pernambuco. At the clinic, 116 (89%) of 131 patients experienced visual disturbances, nausea, and vomiting after routine hemodialysis treatment on 13-20 February 1996. Subsequently, 100 patients developed acute liver failure, and of these 76 died. As of December 1996, 52 of the deaths could be attributed to a common syndrome now called Caruaru syndrome. Examination of phytoplankton from the dialysis clinic's water source, analyses of the clinic's water treatment system, plus serum and liver tissue of clinic patients led to the identification of two groups of cyanobacterial toxins, the hepatotoxic cyclic peptide microcystins and the hepatotoxic alkaloid cylindrospermopsin. Comparison of victims' symptoms and pathology using animal studies of these two cyanotoxins leads us to conclude that the major contributing factor to death of the dialyses patients was intravenous exposure to microcystins, specifically microcystin-YR, -LR, and -AR. From liver concentrations and exposure volumes, it was estimated that 19.5 mug/L microcystin was in the water used for dialysis treatments. This is 19.5 times the level set as a guideline for safe drinking water supplies by the World. Health Organization.

Further studies on an intermediate host murine model showing that a primary Echinococcus granulosus infection is protective against subsequent oncospheral challenge

We describe the use of a murine model to evaluate resistance against subsequent challenge following a primary infection with oncospheres of Echinococcus granulosus. Mice (Kunming strain) were infected with hatched oncospheres of Echinococcus granulosus; 21 days later a second challenge was given by a different route of infection. A primary infection by intraperitoneal (i.p.) injection stimulated 100 and 90.5% protection in terms of reduced cyst numbers against a secondary infection given subcutaneously (s.c.) or intravenously (i.v.) respectively. A primary infection given s.c. followed by i.p. or i.v. challenge resulted in 84.0 and 100% protection, respectively. Intravenous infection followed by i.p. or s.c. challenge resulted in 98.5 and 69.4% protection, respectively. With the i.v. route of infection, almost all resultant cysts were present in the lungs. The data show that a primary infection with oncospheres can induce total or a high degree of protection against a subsequent challenge and confirms that natural (concomitant) immunity can be stimulated in the intermediate host as the result of a primary infection. This may explain the decline in hydatid infection in sheep older than 2 years in hyper-endemic areas such as those found in Xingjiang, China. These older sheep may have been earlier infected and have subsequently self-cured, with the primary infection stimulating an immune response that protects the intermediate host animals from further infection. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.

Pharmacokinetics of ciprofloxacin in ICU patients on continuous veno-venous haemodiafiltration

Objectives: To investigate the pharmacokinetics of intravenous ciprofloxacin 200 mg every 8 h in critically ill patients on continuous veno-venous haemodiafiltration (CVVHDF), one form of continuous renal replacement therapy (CRRT). Design and setting: Open, prospective clinical study in a multidisciplinary, intensive care unit in a university-affiliated tertiary referral hospital. Patients: Sis critically ill patients with acute renal failure on CVVHDF. Interventions: Timed blood and ultrafiltrate samples were collected to allow pharmacokinetics and clearances to be calculated of initial and subsequent doses of 200 mg intravenous ciprofloxacin. CVVHD was performed with 1 l/h of dialysate and 2 l/h of predilution filtration solution, producing 3 lih of dialysis effluent. The blood was pumped at 200 ml/min using a Gambro BMM-10 blood pump through a Hospal AN69HF haemofilter,. Measurements and results: Ten pharmacokinetic profiles were measured. The CVVHDF displayed a urea clearance of 42 +/- 3 ml/min, and removed ciprofloxacin with a clearance of 37 +/- 7 ml/min. This rate was 2-2.5 greater than previously published for ciprofloxacin in other forms of CRRT. On average the CVVHDF was responsible for clearing a fifth of all ciprofloxacin eliminated (21 +/- 10%). The total body clearance of ciprofloxacin was 12.2 +/- 4.3 l/h. The trough concentration following the initial dose was 0.7 +/- 0.3 mg/l. The area under the plasma concentration time curves over a 24-h period ranged from 21 to 55 mg .h l(-1). Conclusions: Intravenous ciprofloxacin 600 mg/day in critically ill patients using this form of CRRT produced adequate plasma levels for many resistant microbes found in intensive care units.

Clinical trials with glycoprotein IIB/IIIA antagonists - No benefit without bleeding?

As the glycoprotein GPIIb/IIIa receptor is the final common pathway in platelet aggregation, antagonists of this receptor cause a profound inhibition of aggregation induced by any agonist. The short-term efficacy and safety of GPIIb/IIIa antagonists in patients undergoing coronary angioplasty was demonstrated with murine 7E3 Fab, but this antibody was immunogenic. Abciximab is a chimeric human-mouse monoclonal antibody that is less immunogenic. The first major trial with a GPIIb/IIIa antagonist was the EPIC trial with abciximab, which showed that abciximab reduced the ischemic complications of coronary balloon angioplasty and atherectomy in high-risk patients, but increased the risk of bleeding. Subsequent studies showed that using less concurrent heparin reduced bleeding. Abciximab also reduced the rate of revascularization. Further studies have shown that the benefits of abciximab extended to all patients undergoing angioplasty (EPILOG), including patients with unstable angina (CAPTURE) and acute myocardial infarction (RAPPORT). Clinical trials with eptifibatide and tirofiban have failed to demonstrate benefit, at the doses used, in angioplasty. Abciximab and eptifibatide, but not oral xemilofiban, improve the safety of the coronary stenting procedure. Shortterm intravenous treatment with lamifiban, eptifibatide or tirofiban is beneficial in acute coronary syndromes (unstable angina, non-Q wave myocardial infarction). Orally active GPIIb/IIIa antagonists are being developed for use in acute coronary syndromes and myocardial infarction. However, no benefit has been shown with lefradafiban in acute coronary syndromes and sibrafiban and orbofiban are harmful. Eptifibatide, lamifiban and abciximab improve coronary patency in myocardial infarction, and long-term trials of GPIIb/IIIa antagonists are being conducted in acute myocardial infarction. Abciximab can cause thrombocytopenia, and all the GPIIb/IIIa antagonists increase the incidence of bleeding, but there is no excess of intracranial hemorrhage. (C) 2001 Prous Science. All rights reserved.

Pharmacotherapy of intermittent claudication

Intermittent claudication (IC) is leg muscle pain, cramping and fatigue brought on by exercise and is the primary symptom of peripheral arterial disease. The goals of pharmacotherapy for IC are to increase the walking capacity/quality of life and to decrease rates of amputation. In 1988, pentoxifylline was the only drug that had reasonable supportive clinical trial evidence for being beneficial in IC. Since then a number of drugs have shown benefit or potential in IC. Cilostazol, a specific inhibitor of phosphodiesterase 3 and activator of lipoprotein lipase, clearly increases pain-free and absolute walking distances in claudicants. However, cilostazol does cause minor side effects including headache, diarrhoea, loose stools and flatulence. Naftidrofuryl, a serotonin (5-HT2) receptor antagonist and antiplatelet drug, is beneficial in claudicants. Inhibitors of platelet aggregation (including nitric oxide from L-arginine or glyceryl trinitrate) and anticoagulants (low molecular weight heparin, defibrotide) probably have both short and long-term benefits in IC. In addition, intravenous infusions of prostaglandins (PGs) PGE1 and PGI2 have an established role in severe peripheral arterial disease and the recent introduction of longer lasting and/or oral forms of the PGs makes them more likely to be useful in the IC associated with less severe forms of the disease. There are some exciting new approaches to the treatment of IC, including propionyl-L-carnitine and basic fibroblast growth factor (bFGF).

Amiodarone - waxed and waned and waxed again

Amiodarone has been used as an anti-arrhythmic drug since the 1970s and has an established role in the treatment of ventricular tachyarrhythmias. Although considered to be a class III anti-arrhythmic, amiodarone also has class I, II and IV actions, which gives it a unique pharmacological and anti-arrhythmic profile. Amiodarone is a structural analogue of thyroid hormone and some of its anti-arrhythmic properties and toxicity may be attributable to interactions with nuclear thyroid hormone receptors. The lipid solubility of amiodarone gives it an exceptionally long half-life. Oral amiodarone takes days to work in ventricular tachyarrhythmias, but iv. amiodarone has immediate effect and can be used in life threatening ventricular arrhythmias. Intravenous amiodarone administered after out-of-hospital cardiac arrest due to ventricular fibrillation improves survival to hospital admission. Many survivors of myocardial infarction (MI) die during the subsequent year, probably due to ventricular arrhythmia. Amiodarone reduces sudden death after MI and this benefit is predominantly observed in patients with preserved cardiac function. Sudden cardiac death, predominantly due to ventricular arrhythmias, is also commonly seen in patients with heart failure. The Grupo de Estudio de la Sobrevida en lsuficiencia Cardiaca en Argentina (GESICA) and Estudio Piloto Argentino de Muerte Subita y Amiodarona (EPAMSA) trials showed survival benefit of amiodarone in heart failure, whereas Congestive Heart Failure-Survival Trial of Anti-arrhythmic Therapy (CHF-STAT) did not. Subsequent meta-analysis established a survival benefit of amiodarone in heart failure. Implanted Cardioverter Defibrillators (ICDs) also give survival benefit to patients at risk of sudden death. In patients with a history of ventricular fibrillation or haemodynamically-compromising ventricular tachycardia, ICDs have been shown to be superior to anti-arrhythmic drugs, principally amiodarone. Further analysis has been undertaken to ascertain which patients are most likely to benefit from ICDs, as these are more expensive than treatment with amiodarone. Patients with severely depressed ejection fractions should be the first to be considered for ICDs. A new indication for amiodarone is atrial fibrillation or flutter. Amiodarone is effective in chronic and recent onset atrial fibrillation and orally or iv. for atrial fibrillation after heart surgery. In atrial fibrillation amiodarone is more than or equi-effective with flecainide, quinidine, racemic sotalol, propafenone and diltiazem and therefore should be considered for first line therapy. Amiodarone is also safe and effective in controlling refractory tachyarrhythmias in infants and is safe after cardiac surgery.