Changes in pentobarbital induced sleeping-time in mice infected with Schistosoma mansoni and immunosuppressed

To evaluate whether the intensity of the hepatic granulomatous response induced by S. mansoni eggs plays a role in drug metabolism, mice were infected with 40 cercariae and tested to assess the sodic pentobarbital induced sleeping-time. To decrease the inflammatory reaction the animals were irradiated with 400 Rad or received azathioprine, 20mg/kg, 3 times a week, for 4 weeks, respectively in or beginning in the 33th post-infection day. In infected animals receiving azathioprine the area of the hepatic granulomas was smaller and the sleeping-time was similar to that of non-infected ones (controls). In mice infected and irradiated the granuloma dimensions were similar to those of animals only infected, in these two latter groups of animals, the sleeping-time was more prolonged than that of the control animals. These results show that: 1) mice with unaltered hepatic granulomatous reaction show reduction in metabolism of sodic pentobarbital; 2) granulomatous response diminished by azathioprine does not interfere with the capacity of metabolism of the anesthetic drug.

Importância do metabolismo no planejamento de fármacos

It is widely recognized that pharmacokinetic optimization needs to be addressed early in drug discovery to reduce the high failure rate in bringing drugs to market. Poor absorption, too short duration of action due to high elimination rate, or the presence of active metabolites are examples of properties that can potentially lead to unsuccessful clinical programmes. Here I describe a brief overview of advantages and molecular strategies for improving metabolic and pharmacokinetic properties applied to the discovery of fluconazol, beta-blockers, ritonavir and ezetimibe and to the development of the prodrugs enalapril and bambuterol.

Sex-dependent differences in the activities of acetylsalicylic acid-esterases in mouse kidneys

Acetylsalicylic acid (ASA), the most used drug worldwide, is hydrolyzed to salicylic acid and acetate by esterases present in tissues of several species including humans. Sex differences in drug metabolism by rodent liver are documented in the literature. In this paper we report a difference in the activities of the esterases (ASA-esterase I and II) in the kidneys of male and female mice. In this species there is no difference between males and females in liver ASA-esterases (ASA-esterase I: males 38.5 ± 7.9 (N = 5) and females 31.6 ± 7.6 (N = 5) nmol of salicylic acid formed min-1 mg protein-1, P>0.05; ASA-esterase II: males 77.3 ± 17.4 (N = 5) and females 61.4 ± 15.1 (N = 5) nmol of salicylic acid formed min-1 mg protein-1, P>0.05). However, in the kidneys males presented a much higher enzyme activity than females (ASA-esterase I: males 25.2 ± 6.3 (N = 5) and females 6.8 ± 0.6 (N = 5) nmol of salicylic acid formed min-1 mg protein-1, P<0.0002; ASA-esterase II: males 79.8 ± 10.1 (N = 5) and females 13.0 ± 1.1 (N = 5) nmol of salicylic acid formed min-1 mg protein-1, P<0.0001). The difference between sexes observed in mouse kidneys could serve as a model to study the molecular basis of this sex difference and also to determine the possible involvement of pituitary and gonadal hormones in this difference in ASA-esterase activities since these hormones control the sex differences in rodent liver enzyme activity.

Albendazole metabolism in patients with neurocysticercosis: antipyrine as a multifunctional marker drug of cytochrome P450

The present study investigates the isoform(s) of cytochrome P450 (CYP) involved in the metabolism of albendazole sulfoxide (ASOX) to albendazole sulfone (ASON) in patients with neurocysticercosis using antipyrine as a multifunctional marker drug. The study was conducted on 11 patients with neurocysticercosis treated with a multiple dose regimen of albendazole for 8 days (5 mg/kg every 8 h). On the 5th day of albendazole treatment, 500 mg antipyrine was administered po. Blood and urine samples were collected up to 72 h after antipyrine administration. Plasma concentrations of (+)-ASOX, (-)-ASOX and ASON were determined by HPLC using a chiral phase column and detection by fluorescence. The apparent clearance (CL/f) of ASON and of the (+) and (-)-ASOX enantiomers were calculated and compared to total antipyrine clearance (CL T) and the clearance for the production of the three major antipyrine metabolites (CLm). A correlation (P<=0.05) was obtained only between the CL T of antipyrine and the CL/f of ASON (r = 0.67). The existence of a correlation suggests the involvement of CYP isoforms common to the metabolism of antipyrine and of ASOX to ASON. Since the CL T of antipyrine is a general measure of CYP enzymes but with a slight to moderate weight toward CYP1A2, we suggest the involvement of this enzyme in ASOX to ASON metabolism in man. The study supports the establishment of a specific marker drug of CYP1A2 in the study of the in vivo metabolism of ASOX to ASON.

Pharmacokinetic aspects of Tert-Butylaminoethyl disulfide, an experimental drug against schistosomiasis in mice

A preliminary study of the pharmacokinetic parameters of t-Butylaminoethyl disulfide was performed after administration of two different single doses (35 and 300 mg/kg) of either the cold or labelled drug. Plasma or blood samples were treated with dithiothreitol, perchloric acid, and, after filtration, submitted to further purification with anionic resein. In the final step, the drug was retained on a cationic resin column, eluted with NaCl 1M and detected according to the method of Ellman (1958). Alternatively, radioactive drug was detected by liquid scintillation counting. The results corresponding to the smaller dose of total drug suggested a pharmacokinetic behavior related to a one open compartment model with the following parameters: area under the intravenous curve (AUC i.v.):671 ± 14; AUC oral: 150 ± 40 µg.min. ml [raised to the power of -1]; elimination rate constant: 0.071 min [raised to the power of -1]; biological half life: 9.8 min; distribution volume: 0.74 ml/g. For the higher dose, the results seemed to obey a more complex undertermined model. Combining the results, the occurence of a dose-dependent pharmacokinetic behavior is suggested, the drug being rapidly absorbed and rapidly eliminated; the elimination process being related mainly to metabolization. The drug seems to be more toxic when administered I.V. because by this route it escapes first pass metabolism, while being quickly distributed to tissues. The maximum tolerated blood level seems to be around 16 µg/ml.

Basic biochemical investigations as rationale for the design of original antimalarial drugs. An example of phospholipid metabolism

The future of antimalarial chemotherapy is particulary alarming in view of the spread of parasite cross-resistances to drugs that are not even structurally related. Only the availability of new pharmacological models will make it possible to select molecules with novel mechanisms of action, thus delaving resistance and allowing the development of new chemotherapeutic strategies. We reached this objective in mice. Our approach is hunged on fundamental and applied research begun in 1980 to investigate to phospholipid (PL) metabolism of intraerythrocytic Plasmodium. This metabolism is abundant, specific and indispensable for the production of Plasmodium membranes. Any drug to interfere with this metabolism blocks parasitic development. The most effective interference yet found involves blockage of the choline transporter, which supplies Plasmodium with choline for the synthesis of phosphatidylcholine, its major PL, this is a limiting step in the pathway. The drug sensitivity thereshold is much lower for the parasite, which is more dependent on this metabolism than host cells. The compounds show in vitro activity against P. falciparum at 1 to 10 nM. They show a very low toxicity against a lymphblastoid cell line, demonstrating a total abscence of correlation between growth inhibition of parasites and lymphoblastoid cells. They show antimalarial activity in vivo, in the P. berghei or P. chabaudi/mouse system, at doses 20-to 100-fold lower than their in acute toxicity limit. The bioavailability of a radiolabeled form of the product seemed to be advantageous (slow blood clearance and no significant concentration in tissues). Lastly, the compounds are inexpensive to produce. They are stable and water-soluble.

Present development concerning antimalarial activity of phospholipid metabolism inhibitors with special reference to in vivo activity

The systematic screening of more than 250 molecules against Plasmodium falciparum in vitro has previously shown that interfering with phospholipid metabolism is lethal to the malaria parasite. These compounds act by impairing choline transport in infected erythrocytes, resulting in phosphatidylcholine de novo biosynthesis inhibition. A thorough study was carried out with the leader compound G25, whose in vitro IC50 is 0.6 nM. It was very specific to mature parasites (trophozoïtes) as determined in vitro with P. falciparum and in vivo with P. chabaudi -infected mice. This specificity corresponds to the most intense phase of phospholipid biosynthesis activity during the parasite cycle, thus corroborating the mechanism of action. The in vivo antimalarial activity (ED50) against P. chabaudi was 0.03 mg/kg, and a similar sensitivity was obtained with P. vinckei petteri, when the drug was intraperitoneally administered in a 4 day suppressive test. In contrast, P. berghei was revealed as less sensitive (3- to 20-fold, depending on the P. berghei-strain). This difference in activity could result either from the degree of synchronism of every strain, their invasion preference for mature or immature red blood cells or from an intrinsically lower sensitivity of the P. berghei strain to G25. Irrespective of the mode of administration, G25 had the same therapeutic index (lethal dose 50 (LD50)/ED50) but the dose to obtain antimalarial activity after oral treatment was 100-fold higher than after intraperitoneal (or subcutaneous) administration. This must be related to the low intestinal absorption of these kind of compounds. G25 succeeded to completely inhibiting parasitemia as high as 11.2% without any decrease in its therapeutic index when administered subcutaneously twice a day for at least 8 consecutive days to P. chabaudi -infected-rodent model. Transition to human preclinical investigations now requires a synthesis of molecules which would permit oral absorption.

Infected erythrocyte choline carrier inhibitors: exploring some potentialities inside Plasmodium phospholipid metabolism for eventual resistance acquisition

We have developed a model for designing antimalarial drugs based on interference with an essential metabolism developed by Plasmodium during its intraerythrocytic cycle, phospholipid (PL) metabolism. The most promising drug interference is choline transporter blockage, which provides Plasmodium with a supply of precursor for synthesis of phosphatidylcholine (PC), the major PL of infected erythrocytes. Choline entry is a limiting step in this metabolic pathway and occurs by a facilitated-diffusion system involving an asymmetric carrier operating according to a cyclic model. Choline transport in the erythrocytes is not sodium dependent nor stereospecific as demonstrated using stereoisomers of alpha and beta methylcholine. These last two characteristics along with distinct effects of nitrogen substitution on transport rate demonstrate that choline transport in the infected erythrocyte possesses characteristics quite distinct from that of the nervous system. This indicates a possible discrimination between the antimalarial activity (inhibition of choline transport in the infected erythrocyte) and a possible toxic effect through inhibition of choline entry in synaptosomes. Apart from the de novo pathway of choline, PC can be synthesized by N-methylation from phosphatidylethanolamine (PE). There is a de novo pathway for PE biosynthesis from ethanolamine in infected cells but phosphatidylserine (PS) decarboxylation also occurs. In addition, PE can be directly and abundantly synthesized from serine decarboxylation into ethanolamine, a pathway which is absent from the host. The variety of the pathways that exist for the biosynthesis of one given PL led us to investigate whether an equilibrium can occur between all PL metabolic pathways. Indeed, if alternative (compensative) pathway(s) can operate after blockage of the de novo PC biosynthesis pathway this would indicate a potential mechanism for resistance acquisition. Up until now, there is no evidence of such a compensative process occurring in Plasmodium-infected erythrocytes under physiological conditions. Besides, the discovery of a highly parasite-specific pathway (serine decarboxylation and the presence of PS synthase) constitutes a very attractive and promising target, which could be attacked if resistances are built up against choline analogs. Indeed, potential inhibitions of the serine decarboxylase pathway could be very useful in acting instead of, or in surgery with, choline analogs.

A new approach for potential drug target discovery through in silico metabolic pathway analysis using Trypanosoma cruzi genome information

The current drug options for the treatment of chronic Chagas disease have not been sufficient and high hopes have been placed on the use of genomic data from the human parasite Trypanosoma cruzi to identify new drug targets and develop appropriate treatments for both acute and chronic Chagas disease. However, the lack of a complete assembly of the genomic sequence and the presence of many predicted proteins with unknown or unsure functions has hampered our complete view of the parasite's metabolic pathways. Moreover, pinpointing new drug targets has proven to be more complex than anticipated and has revealed large holes in our understanding of metabolic pathways and their integrated regulation, not only for this parasite, but for many other similar pathogens. Using an in silicocomparative study on pathway annotation and searching for analogous and specific enzymes, we have been able to predict a considerable number of additional enzymatic functions in T. cruzi. Here we focus on the energetic pathways, such as glycolysis, the pentose phosphate shunt, the Krebs cycle and lipid metabolism. We point out many enzymes that are analogous to those of the human host, which could be potential new therapeutic targets.

Computational drug design strategies applied to the modelling of human immunodeficiency virus-1 reverse transcriptase inhibitors

Reverse transcriptase (RT) is a multifunctional enzyme in the human immunodeficiency virus (HIV)-1 life cycle and represents a primary target for drug discovery efforts against HIV-1 infection. Two classes of RT inhibitors, the nucleoside RT inhibitors (NRTIs) and the nonnucleoside transcriptase inhibitors are prominently used in the highly active antiretroviral therapy in combination with other anti-HIV drugs. However, the rapid emergence of drug-resistant viral strains has limited the successful rate of the anti-HIV agents. Computational methods are a significant part of the drug design process and indispensable to study drug resistance. In this review, recent advances in computer-aided drug design for the rational design of new compounds against HIV-1 RT using methods such as molecular docking, molecular dynamics, free energy calculations, quantitative structure-activity relationships, pharmacophore modelling and absorption, distribution, metabolism, excretion and toxicity prediction are discussed. Successful applications of these methodologies are also highlighted.

An integrative review of drug utilization by the elderly in primary health care

ABSTRACT OBJECTIVE To identify knowledge produced about drug utilization by the elderly in the primary health care context from 2006 to 2014. METHOD An integrative review of the PubMed, LILACS, BDENF, and SCOPUS databases, including qualitative research papers in Portuguese, English, and Spanish. It excluded papers with insufficient information regarding the methodological description. RESULTS Search found 633 papers that, after being subjected to the inclusion and exclusion criteria, made up a corpusof 76 publications, mostly in English and produced in the United States, England, and Brazil. Results were pooled in eight thematic categories showing the current trend of drug use in the elderly, notably the use of psychotropics, polypharmacy, the prevention of adverse events, and adoption of technologies to facilitate drug management by the elderly. Studies point out the risks posed to the elderly as a consequence of changes in metabolism and simultaneous use of several drugs. CONCLUSION There is strong concern about improving communications between professionals and the elderly in order to promote an exchange of information about therapy, and in this way prevent major health complications in this population.

Epidemiological methods for research with drug misusers: review of methods for studying prevalence and morbidity

Epidemiological studies of drug misusers have until recently relied on two main forms of sampling: probability and convenience. The former has been used when the aim was simply to estimate the prevalence of the condition and the latter when in depth studies of the characteristics, profiles and behaviour of drug users were required, but each method has its limitations. Probability samples become impracticable when the prevalence of the condition is very low, less than 0.5% for example, or when the condition being studied is a clandestine activity such as illicit drug use. When stratified random samples are used, it may be difficult to obtain a truly representative sample, depending on the quality of the information used to develop the stratification strategy. The main limitation of studies using convenience samples is that the results cannot be generalised to the whole population of drug users due to selection bias and a lack of information concerning the sampling frame. New methods have been developed which aim to overcome some of these difficulties, for example, social network analysis, snowball sampling, capture-recapture techniques, privileged access interviewer method and contact tracing. All these methods have been applied to the study of drug misuse. The various methods are described and examples of their use given, drawn from both the Brazilian and international drug misuse literature.

Risk of drug interaction: combination of antidepressants and other drugs

OBJECTIVE: To assess the frequency of combination of antidepressants with other drugs and risk of drug interactions in the setting public hospital units in Brazil. METHODS: Prescriptions of all patients admitted to a public hospital from November 1996 to February 1997 were surveyed from the hospital's data processing center in São Paulo, Brazil. A manual search of case notes of all patients admitted to the psychiatric unit from January 1993 to December 1995 and all patients registered in the affective disorders outpatient clinic in December 1996 was carried out. Patients taking any antidepressant were identified and concomitant use of drugs was checked. By means of a software program (Micromedex®) drug interactions were identified. RESULTS: Out of 6,844 patients admitted to the hospital, 63 (0.9%) used antidepressants and 16 (25.3%) were at risk of drug interaction. Out of 311 patients in the psychiatric unit, 63 (20.2%) used antidepressants and 13 of them (20.6%) were at risk. Out of 87 patients in the affective disorders outpatient clinic, 43 (49.4%) took antidepressants and 7 (16.2%) were at risk. In general, the use of antidepressants was recorded in 169 patients and 36 (21.3%) were at risk of drug interactions. Twenty different forms of combinations at risk of drug interactions were identified: four were classified as mild, 15 moderate and one severe interaction. CONCLUSION: In the hospital general units the number of drug interactions per patient was higher than in the psychiatric unit; and prescription for depression was lower than expected.

Drug abuse among workers in Brazilian regions

OBJECTIVE: Many business organizations in Brazil have adopted drug testing programs in the workplace since 1992. Rehabilitation, rather than layoff and disciplinary measures, has been offered as part of the Brazilian employee assistance programs. The purpose study is to profile drug abuse among company workers of different Brazilian geographical regions. METHODS: Urine samples of 12,700 workers from five geographical regions were tested for the most common illicit drugs of abuse in the country: marijuana, cocaine, and amphetamine. Enzyme multiplied immunoassay technique (EMIT) and gas chromatography coupled with mass spectrometry (GC/MS) were the techniques utilized for urine testing. The distribution of collected urine samples according to geographical regions was: 72.0% southeast, 13.8% northeast, 7.9% south, 5.7% central west and 0.6% north. RESULTS: Of all samples analyzed, 1.8% was found to be positive for drugs: 0.5% from the south region, 1.1% from northeast, 1.2% from central west, 1.3% from north, and 2.2% from southeast. Of these, 59.9% was marijuana, 17.7% cocaine, 14.6% amphetamine, and 7.7% associated drugs. CONCLUSIONS: The distribution of drugs found in the samples shows a regional variation. Marijuana, however, was found in all regions. Cocaine was seen only in central west and southeast regions. Amphetamine was found in northeast, central west, and southeast regions.

Metabolic changes associated with antiretroviral therapy in HIV-positive patients

OBJECTIVE: To evaluate metabolic changes associated with highly active antiretroviral therapy (HAART) in HIV-positive patients, and to identify risk factors associated. METHODS: Retrospective study that included 110 HIV-positive patients who where on HAART in the city of Porto Alegre (Southern Brazil) between January 2003 and March 2004. Data on demographic variables, cigarette smoking, diabetes mellitus, cholesterol and triglyceride levels, stage of HIV infection, antiretroviral therapy and HCV coinfection were collected. General linear models procedure for repeated measures was used to test the interaction between HAART and HCV coinfection or protease inhibitor treatment. RESULTS: Total cholesterol, triglycerides, and glucose levels significantly increased after receiving HAART (p<0.001 for all variables), but no interaction with protease inhibitors was seen for total cholesterol, glucose and triglyceride levels (interaction treatment*protease inhibitors p=0.741, p=0.784, and p=0.081, respectively). An association between total cholesterol levels and HCV coinfection was found both at baseline and follow-up (effect of HCV coinfection, p=0.011). Glucose levels were increased by HAART (treatment effect, p=0.036), but the effect was associated to HCV coinfection (treatment*HCV effect, p=0.018). Gender, smoking habit, intravenous drug use and age were not significantly associated with cholesterol, triglyceride and glucose changes. CONCLUSIONS: HCV-infected patients at baseline were significantly less likely to develop hypercholesterolemia. The results provide further evidence of the role of HAART for the development of metabolic disturbances.