Current Clinical Pharmacology - Volume 8, Issue 4, 2013

Diabetes and hypertension frequently coexist and constitute the most notorious combination for the pathogenesis of DR. Large clinical trials have clearly demonstrated that tight control of glycaemia and/or blood pressure significantly reduces the incidence and progression of DR. The mechanism by which hypertension interacts with diabetes to exacerbate the retinal disease is not completely understood. From experimental studies, increasing evidence demonstrates that chronic inflammation and oxidative stress are involved. In the present review, we summarize data obtained from our research along with those from other groups to better understand the role of hypertension in the pathogenesis of DR. It is suggested that oxidative stress and inflammation may be common denominators of retinal damage in the presence of hypertension in diabetic patients.

Hyperglycemia, a prominent characteristic of diabetes, has been implicated in the apoptotic death of vascular and neuronal cells in the retina. In diabetic retinopathy, mitochondrial dysfunction, endoplasmic reticulum (ER) stress, and subsequent breakdown of cellular homeostasis play a critical role in retinal cell death. In particular, changes in mitochondrial morphology, mitochondrial membrane potential heterogeneity, oxygen consumption rate and protein misfolding are beginning to be recognized as key players in the demise of retinal vascular cells in diabetes. Some of these key changes contribute to oxidative stress and influence ion transport, impacting overall cellular homeostasis. The primary objective of this review is to provide insight into the mechanisms in which high glucose influences two disparate cellular organelles, mitochondria and ER, in promoting apoptotic demise of retinal vascular and neuronal cells in diabetic retinopathy.

Diabetic retinopathy is a major cause of vision impairment and blindness and represents a significant health burden throughout the world. There is considerable interest in developing new treatments that retard the progression of diabetic retinopathy from its early to proliferative stages. It could be argued that the absence of an ideal therapy for diabetic retinopathy comes from an incomplete understanding about the biochemical mechanisms that underlie this disease, and their precise impact on specific retinal cell populations. Findings from pre-clinical and clinical studies indicate that both the renin-angiotensin system (RAS) and advanced glycation end-products (AGEs) influence various aspects of diabetic retinopathy. Of interest is growing evidence of cross-talk between the RAS and AGEs pathways. This review will discuss the role of both the RAS and AGEs in diabetic retinopathy, and how the identification of interactions between the two pathways may have implications for the development of new treatment strategies.

Cardiopulmonary bypass (CPB) is known to have important effects on the disposition of drugs, which in turn may have important implications for the efficacy and toxicity of drug therapy. These effects constantly change throughout CPB and some continue to exert influence after the patient has been successfully weaned. In children, developmental and disease specific changes in drug disposition and effect also need to be taken into account when studying the effects of CPB. This review will provide an extensive overview of the current literature concerning the mechanisms behind the effects CPB has on pharmacokinetic and pharmacodynamic parameters. Also the effects of CPB on individual anesthetic drugs and sedatives, opioids, neuromuscular blocking agents, antibiotics and miscellaneous medications will be reviewed. Special attention will be paid to the pediatric population.

Background: Retigabine is an antiepileptic drug that reduces neuronal excitability by enhancing potassium channel activity. Methods: This manuscript summarizes the pharmacokinetic and biopharmaceutical properties of retigabine collated from published and unpublished in vitro and clinical phase I-III studies in healthy volunteers or patients with partial-onset seizures. Results: Retigabine is rapidly absorbed with a median time to Cmax of 0.5-2.0 hours. Thereafter, plasma concentrations decline in a mono-exponential manner, with a median half-life of 6-8 hours. The absolute oral bioavailability of retigabine is &sim60&percnt. Retigabine is metabolized extensively by N-acetylation and subsequent N-glucuronidation. In vitro and in vivo studies have shown that the drug-interaction potential of retigabine is low. The pharmacokinetics of retigabine are linear over the dose range 200-400mg three times daily (tid), with &sim35-50&percnt between-subject variability. Systemic exposure was not affected by a high fat meal, but Cmax was, &sim14&percnt and &sim38&percnt higher in the fed versus fasted state for the 200 and 400mg tablets, respectively. Retigabine drug-related material is primarily eliminated renally with unchanged retigabine accounting for &sim36&percnt. Retigabine plasma clearance decreased as severity of renal or hepatic impairment increased. Systemic exposure to retigabine is unaffected by gender when normalized for body weight. In elderly patients, retigabine systemic exposure was higher, and half-life was longer than in younger patients. Conclusions: Retigabine should be administered tid without regard to food. No adjustments required for gender, race, or genetic/polymorphisms. Dosage adjustments are recommended in elderly patients and those with moderate and severe renal or moderate hepatic impairment.

Background: We present herein, a comparative study assessing the bactericidal kinetics of tigecycline, doxycycline, cefazolin and vancomycin against several methicllin-susceptible (MSSA) and –resistant (MRSA) Staphylococcus aureus isolates recovered from patients of 24 different cities in Argentina. Methods: After genotypic characterization, 20 strains (10 MRSA and 10 MSSA) were selected for time-kill studies. Results: Vancomycin showed bactericidal effect (i.e. ≥3-log10 CFU/mL decrease) against 50% and 10% of the MRSA strains at 4 x Minimal Inhibitory Concentration (MIC) and 2xMIC, respectively, after 24 h of incubation and displayed bactericidal activity against all MSSA isolates at 4xMIC. Cefazolin was bactericidal against 30% of MSSA strains at the higher concentration (4xMIC) and against 10% at 2 x MIC and MIC dose concentrations. The bactericidal magnitude of cefazolin observed after 24 h of incubation was lower than the vancomycin one. Albeit bacteriostactic, tigecycline at 2xMIC exerted a -1 to2-log decrease in the viable cell counts after 24-h incubation against 19 of the 20 S. aureus strains. Doxycycline was the least inhibitory of the antibiotics tested against both MRSA and MSSA, displaying no bactericidal activity in any of the cases and showing regrowth after 24 h of incubation at MIC level. Conclusion: Vancomycin at high concentrations showed the best activity. Cefazolin did not show the activity expected for a beta-lactam antibiotic against MSSA. Tigecycline may be a useful option in infections caused by MRSA, where bactericidal activity is not an exclusive requirement and doxycycline does not seem an attractive alternative in serious infections.

Platelet aggregation activity is the cornerstone of the pathogenesis of atherothrombosis and plays a main role in the appearance of major adverse cardiac events (MACE). This aspect has become even more important nowadays due to the use of drug-eluting stents (DES), where a proper platelet inhibition is required. Dual antiplatelet therapy with aspirin and clopidogrel in patients undergoing percutaneous coronary intervention (PCI) has widely demonstrated its beneficial effect in reducing MACE compared with aspirin alone. These benefits had also been established in short and long term treatment in patients with coronary artery disease managed with a conservative strategy. However, despite dual antiplatelet therapy an important number of patients experience new MACE related to an incomplete platelet inhibition that can be caused by the interaction of different mechanisms, not fully known at the moment. Several clinical studies suggested the significant variability in individual patient response to antiplatelet drugs to be due to the use of different laboratory tests. Moreover, other studies associated the low responsiveness status with an increased risk of recurrent cardiovascular events. Notably, resistance or reduced response to antiplatelet therapy with aspirin and clopidogrel is a clinically relevant entity that needs to be taken into account in order to perform a proper and individualized treatment strategy. Recent antiplatelet drugs such as prasugrel and ticagrelor have appeared to be an attractive option for patients with resistance or low response to traditional therapy. In this article we review aspirin and clopidogrel resistance as a clinical entity, the different mechanisms that could be linked to treatment failure, its relation with special situations and future perspectives in this area.

Amphetamine-like drugs are sympathomimetic agents with marked central and peripheral stimulant properties. Despite the street illegal drugs such as amphetamine and ecstasy, some amphetamine-like compounds are also legally marketed under medical prescription in the treatment of attention deficit-hyperactivity disorder (methylphenidate) and obesity/overweight (fenproporex and diethylpropione). However, similar with what happens with their illicit analogues, therapeutic amphetamine-like drugs also share important toxicological risks. Although methylphenidate is considered the first choice in the treatment of attention deficit-hyperactivity disorder, its high popularity among teenagers and children is raising concern in the medical community. Regarding weight-loss purposes, the use of amphetamine-like compounds are very controversial, though. Thus, the present review will address pharmacokinetic, pharmacodynamic, and toxicological aspects of amphetamine-like compounds used with therapeutic aims.

Neurodevelopmental disorders are a large family of conditions of genetic or environmental origin that are characterized by deficiencies in cognitive and behavioral functions. The therapeutic management of individuals with these disorders is typically complex and is limited to the treatment of specific symptoms that characterize each disorder. The neurodevelopmental disorder Rett syndrome (RTT) is the leading cause of severe intellectual disability in females. Mutations in the gene encoding the transcriptional regulator methyl-CpG-binding protein 2 (MECP2), located on the X chromosome, have been confirmed in more than 95% of individuals meeting diagnostic criteria for classical RTT. RTT is characterized by an uneventful early infancy followed by stagnation and regression of growth, motor, language, and social skills later in development. This review will discuss the genetics, pathology, and symptoms that distinguish RTT from other neurodevelopmental disorders associated with intellectual disability. Because great progress has been made in the basic and clinical science of RTT, the goal of this review is to provide a thorough assessment of current pharmacotherapeutic options to treat the symptoms associated with this disorder. Furthermore, we will highlight recent discoveries made with novel pharmacological interventions in experimental preclinical phases, and which have reversed pathological phenotypes in mouse and cell culture models of RTT and may result in clinical trials.

Objective: Second generation antipsychotics (SGA) have gained increased evidence for the treatment of irritability and aggression in children and adolescents with lower functioning autistic disorder. Individuals with Asperger’s Disorder (AD) and High Functioning Autism (HFA) experience significant emotional and behavioral problems and psychiatric comorbidity. There is a need to review the published literature on SGA treatment efficacy in the AD and HFA populations to provide more effective treatment choices for these subgroups. Methods: We conducted a systematic review and meta-analysis of the recent English literature on SGA use in children and adolescents (ages 0-24 years) with AD and HFA using the Medline/PubMed and PsychINFO computerized databases. Key search words were ‘Asperger’, ‘high functioning autism’, ‘autism spectrum disorders (ASD)’, and ‘pervasive developmental disorder (PDD)’ in combination with ‘second generation antipsychotics’, ‘aripiprazole; ‘olanzapine’, ‘quetiapine’, ‘risperidone’, or ‘ziprasidone’. Results: Our search yielded 214 citations, however only open-label or randomized-controlled trials (RCT) with ≥25% of their subjects having an IQ≥71 were included in our review. Eleven original studies met our inclusion parameters for review; eight studies for the meta-analysis. These studies, although limited in methodological rigor, and the meta-analytic results suggest that SGAs provide improvement in behavioral symptoms associated with AD and HFA. The majority of the studies reported weight gain as a potentially concerning adverse effect. Conclusion: There is a lack of robustly conducted trials on the use of SGAs in the management of AD and HFA. More research in pharmacological and psychosocial treatments is warranted. Clinicians are cautioned to approach pharmacological treatment prudently balancing benefit with potential cardiometabolic risk.