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Biomedical subjects

Jose de Leon

Publications and source records attributed to Jose de Leon.

At least 19 recordsLinked to original sources
PubMed2007

Individualizing drug dosage by using a random intercept linear model.

An algorithm for drug dosage individualization is proposed. The algorithm assumes a random intercept linear model for the log of trough-plasma-concentration-to-dosage ratio of the drug at steady-state, and aims at determining an optimum dosage for producing a trough steady-state plasma concentration within a target concentration range. The minimum number of algorithm steps necessary to find the optimum dosage is computed. Computations are illustrated for clozapine, an antipsychotic drug used to treat patients with severe schizophrenia.

Algorithms↗
PubMed2007

Weight gain during a double-blind multidosage clozapine study.

Possible variables associated with weight gain during clozapine treatment include dosing, treatment duration, baseline body mass index (BMI), sex, and plasma norclozapine concentrations. Weight gains during a double-blind, randomized clozapine study using 100-, 300-, and 600-mg/d doses were analyzed. It was hypothesized that weight gain was associated with baseline BMI, clozapine dosing, and demographic factors. The possible contribution of plasma clozapine and norclozapine concentrations was explored. Fifty treatment-refractory schizophrenia patients were randomized to 100-, 300-, or 600-mg/d doses of clozapine for a 16-week, double-blind treatment in a research ward. Nonresponsive patients went onto a second and/or a third 16-week, double-blind treatment at the other doses. Weights of patients were measured every week. During the first clozapine treatment, weight gain varied across 3 baseline BMI categories (normal-weight patients [4.1 kg, P < 0.001], overweight patients [2.6 kg, P = 0.05], and obese patients [0.36 kg, not significant]) and according to dosing (600 mg/d [4.4 kg], 300 mg/d [2.6 kg], and 100 mg/d [1.3 kg]). Sex had no effect after controlling for baseline BMI and dose, but the African-American race had a strong significant effect despite the small number of African Americans (n = 6). At the end of the first clozapine treatment, plasma norclozapine concentration was not significantly correlated with weight gain in the total sample (r = 0.16, P = 0.32, n = 43), but seems to be strongly correlated in nonsmokers. Despite its limitations, this study indicates that baseline BMI, dosing, and, possibly, the African-American race may be major determinants of clozapine-induced weight gain.

Antipsychotic Agents↗
PubMed2007

Metabolic drug interactions with newer antipsychotics: a comparative review.

Newer antipsychotics introduced in clinical practice in recent years include clozapine, risperidone, olanzapine, quetiapine, sertindole, ziprasidone, aripiprazole and amisulpride. These agents are subject to drug-drug interactions with other psychotropic agents or with medications used in the treatment of concomitant physical illnesses. Most pharmacokinetic interactions with newer antipsychotics occur at the metabolic level and usually involve changes in the activity of the major drug-metabolizing enzymes involved in their biotransformation, i.e. the cytochrome P450 (CYP) monooxygenases and/or uridine diphosphate-glucuronosyltransferases (UGT). Clozapine is metabolized primarily by CYP1A2, with additional contribution by other CYP isoforms. Risperidone is metabolized primarily by CYP2D6 and, to a lesser extent, CYP3A4. Olanzapine undergoes both direct conjugation and CYP1A2-mediated oxidation. Quetiapine is metabolized by CYP3A4, while sertindole and aripiprazole are metabolized by CYP2D6 and CYP3A4. Ziprasidone pathways include aldehyde oxidase-mediated reduction and CYP3A4-mediated oxidation. Amisulpride is primarily excreted in the urine and undergoes relatively little metabolism. While novel antipsychotics are unlikely to interfere with the elimination of other drugs, co-administration of inhibitors or inducers of the major enzymes responsible for their metabolism may modify their plasma concentrations, leading to potentially significant effects. Most documented metabolic interactions involve antidepressant and anti-epileptic drugs. Of a particular clinical significance is the interaction between fluvoxamine, a potent CYP1A2 inhibitor, and clozapine. Differences in the interaction potential among the novel antipsychotics currently available may be predicted based on their metabolic pathways. The clinical relevance of these interactions should be interpreted in relation to the relative width of their therapeutic index. Avoidance of unnecessary polypharmacy, knowledge of the interaction profiles of individual agents, and careful individualization of dosage based on close evaluation of clinical response and, possibly, plasma drug concentrations are essential to prevent and minimize potentially adverse drug interactions in patients receiving newer antipsychotics.

Antipsychotic Agents↗
PubMed2006

The effect of atypical versus typical antipsychotics on tardive dyskinesia: a naturalistic study.

OBJECTIVE: The aim was testing whether atypical antipsychotics (versus typicals) were associated with less risk of tardive dyskinesia (TD) in 516 severely mentally ill patients. METHODS: The sample included 11% (57/516) with no exposure before current treatment with atypicals; 9% (48/516) with prior and current treatment with atypicals but no exposure to typicals; 18% (94/516) with lifetime exposure to typicals for <5 years (plus atypicals); and 62% (317/516) with lifetime exposure to typicals for >or=5 years (plus atypicals). The Abnormal Involuntary Movement Scale (AIMS) was used to assess dyskinetic movements. Following Schooler and Kane's criteria TD was considered present when mild movements were present in at least two body areas or moderate movements were present in at least one body area. RESULTS: TD prevalences were 5% (3/57) in previously naïve patients, 19% (9/48) after exposure only to atypicals, 19% (18/94) after typical exposure of <5 years, and 42% (132/317) after typical exposure of >or=5 years. There was no significant effect comparing those taking only atypicals to those exposed to typicals for <5 years (OR = 1.0, CI 0.42-2.5). CONCLUSION: This study is limited by the naturalistic design, the relatively small samples in the first two groups, the lack of information on the duration of the atypicals and their relatively recent introduction to the market (ziprasidone and aripiprazole were introduced to the market in the middle of the study). This study raises the question that new TD studies need to establish whether decades of treatment with atypical antipsychotics make a difference.

Adult↗
PubMed2006

Does smoking reduce akathisia? Testing a narrow version of the self-medication hypothesis.

BACKGROUND: The self-medication hypothesis proposes that schizophrenia patients smoke to decrease their schizophrenia symptoms or antipsychotic side effects, but they usually start smoking before their illness and heavy smoking is not consistently associated with fewer symptoms or side effects. A narrow version of the self-medication hypothesis, heavy smoking reduces akathisia, is explored. METHOD: The sample included 250 outpatients with DSM-IV schizophrenia assessed with the Positive and Negative Syndrome Scale (PANSS) and the Barnes Akathisia Scale. Prevalences were 69% (173/250) for smoking, 39% (98/250) for heavy smoking (> or =30 cigarettes/day), 7% (17/250) for akathisia (Barnes Global score>1), 14% (35/250) for a broader akathisia definition (Barnes Global score>0) and 20% for excited symptoms (>1 on the PANSS factor score). RESULTS: Heavy smoking was not associated with akathisia (41% of patients with akathisia were heavy smokers versus 39% of patients without akathisia; chi2=0.3, df=1, p=0.86), even after correcting for confounding factors and/or using a broader akathisia definition. Heavy smoking was associated with excited schizophrenia symptoms (possibly reflecting agitation). Particularly in patients taking lower doses of typical antipsychotics, excited symptoms, with or without akathisia, were strongly associated with heavy smoking and appear to interact with patients' reports of smoking's calming effect as the main reason for smoking. CONCLUSION: The self-medication hypothesis does not explain increased smoking and heavy smoking in schizophrenia. Moreover, heavy smoking may be associated with more disturbed brain homeostatic mechanisms. Prospective studies need to explore whether temporary increases in cigarette smoking may be associated with periods of higher agitation, with or without akathisia.

Adult↗
PubMed2006

Fewer but heavier caffeine consumers in schizophrenia: a case-control study.

According to the literature, there is an association between schizophrenia and caffeine consumption, but it is not clear whether schizophrenia is associated with either higher prevalence of daily caffeine intake or the amount consumed. In this study we compared our previously published schizophrenia patients (n=250) with a control sample (n=290) after controlling for demographic variables and tobacco and alcohol consumption. Current caffeine intake was less frequent in schizophrenia patients (59%, 147/250) than in controls (70%, 204/290). In the multivariate analyses, caffeine intake was less frequent at an older age and in schizophrenia patients, and more frequent in smokers and alcohol users. Among caffeine consumers, heavy caffeine intake (> or =200 mg/day) was significantly associated with schizophrenia (64%, 94/147 in schizophrenia versus 36%, 73/204 in controls), as well as older age and smoking. Daily amount of caffeine intake and smoked cigarettes correlated significantly in the schizophrenia group but not in the control group; the correlation of caffeine intake with nicotine dependence was low and non-significant in both groups. The association between current smoking and heavy caffeine intake may be partly explained by a pharmacokinetic effect: tobacco smoke compounds induce caffeine metabolism by the cytochrome P450 1A2. Although schizophrenia by itself may be associated with heavy caffeine intake in caffeine users, part of this association was explained by the association between schizophrenia and smoking. The relationship between caffeine and alcohol intake appeared to be more complex; alcohol and caffeine use were significantly associated, but within caffeine users alcohol was associated with less frequent heavy caffeine consumption among smokers. In future studies, the measurement of plasma caffeine levels will help both to better define heavy caffeine intake and to control for smoking pharmacokinetic effects.

Adolescent↗
PubMed2006

Association between the T102C polymorphism of the serotonin-2A receptor gene and schizophrenia.

Studies have shown an association between the T102C polymorphism of the 5HT2a receptor gene and schizophrenia. However, negative findings have also been reported. We conducted a case-control study of the T102C polymorphism in Spanish Caucasians. We compared T102C polymorphism genotypes and allele frequencies in 188 schizophrenia patients and 440 healthy controls. There were significant differences in the distribution of the three genotypes (TT, TC and CC) and in the allele frequencies in controls and schizophrenics. The C allele was more frequent in schizophrenia patients than in healthy controls. The Cochrane-Armitage test for trend indicated a significant dosage effect for schizophrenia of the risk allele (C).

Adult↗
PubMed2006

Response to hydrocodone, codeine and oxycodone in a CYP2D6 poor metabolizer.

Codeine is metabolized by the cytochrome P450 2D6 (CYP2D6) to morphine. Codeine is a much weaker agonist at mu opioid receptors than morphine. Therefore, codeine analgesia is highly dependent on CYP2D6 activity. Large prospective studies in the clinical environment do not exist, but it appears reasonable to avoid codeine use in CYP2D6 poor metabolizers (PMs). CYP2D6 metabolizes other opioid analgesics, including tramadol, dihydrocodeine, oxycodone and hydrocodone, although they have been less systematically studied. It is unclear whether these other pro-drugs may be as completely dependent on CYP2D6 for their analgesia as codeine. We describe a patient identified as a CYP2D6 PM with a history of problems with opioid analgesics. The patient was an 85-year-old female Caucasian who had hip surgery. The patient had a long-standing intolerance to codeine. In her first admission, she couldn't tolerate the regimen of oxycodone combined with tramadol prns (as needed). She was genotyped as a CYP2D6 PM and after the information was provided to the treating physician in her second admission, she seemed to have a better response to hydrocodone. Large case-control naturalistic studies followed by randomized trials in patients taking opioid analgesics may be needed to definitively establish that CYP2D6 genotyping has clinical relevance in the use of several opioid analgesics.

Aged, 80 and over↗
PubMed2006

Smoking is associated with schizophrenia, but not with mood disorders, within a population with low smoking rates: a matched case-control study in Bucaramanga, Colombia.

When comparing current smoking in schizophrenia patients versus the general population, the average odds ratio (OR) was 5.3 in a meta-analysis of 42 studies from 20 nations. Limited tobacco access can eliminate this strong association in some nations. Out of the 42 ORs, 37 were significantly higher than 1. Of the 5 non-significant ORs, three came from Colombian studies comparing current smoking prevalences in schizophrenia versus those in the general population (18%). However, the 3 ORs were not adjusted for confounders. We hypothesized that the association between schizophrenia and smoking is so strong that it can be detected in populations with limited access to smoking after carefully controlling for confounders. Of the three Colombian studies, one included 73 schizophrenia patients (DSM-IV schizophrenia or schizoaffective disorder) and 111 patients with mood disorders (DSM-IV bipolar or major depressive disorders). The current study matched each of these patients with 2 controls from the general population and performed more sophisticated statistical analyses. Prevalences of current smoking were 26% for schizophrenia patients and 10% for their matched controls (adjusted Mantel-Haenszel OR=3.1, 95% CI, 1.4-6.8), and 7% for patients with mood disorders and 12% for their matched controls (adjusted Mantel-Haenszel OR=0.62; CI, 0.28-1.4). The previously observed lack of association between schizophrenia and current smoking was due to lack of control of important confounding variables because of the absence of a control group. This re-analysis, which used a careful matching that controlled for confounders, suggests that the association between schizophrenia and smoking behaviors can stand in populations with low monetary income and low smoking rates. This study also suggests that the association between severe mood disorders (bipolar and major depression) and smoking is not as strong as that observed between schizophrenia and smoking, and may not be observable in countries where people have limited economic resources.

Adult↗
PubMed2006

The AmpliChip CYP450 genotyping test: Integrating a new clinical tool.

The AmpliChip CYP450 Test, which analyzes patient genotypes for cytochrome P450 (CYP) genes CYP2D6 and CYP2C19, is a major step toward introducing personalized prescribing into the clinical environment. Interest in adverse drug reactions (ADRs), the genetic revolution, and pharmacogenetics have converged with the introduction of this tool, which is anticipated to be the first of a new wave of such tools to follow over the next 5-10 years. The AmpliChip CYP450 Test is based on microarray technology, which combines hybridization in precise locations on a glass microarray and a fluorescent labeling system. It classifies individuals into two CYP2C19 phenotypes (extensive metabolizers [EMs] and poor metabolizers [PMs]) by testing three alleles, and into four CYP2D6 phenotypes (ultrarapid metabolizers [UMs], EMs, intermediate metabolizers [IMs], and PMs) by testing 27 alleles, including seven duplications. CYP2D6 is a metabolic enzyme with four activity levels (or phenotypes): UMs with unusually high activity; normal subjects, known as EMs; IMs with low activity; and PMs with no CYP2D6 activity (7% of Caucasians and 1-3% in other ethnic groups). Levels of evidence for the association between CYP2D6 PMs and ADRs are relatively reasonable and include systematic reviews of case-control studies of some typical antipsychotics and tricyclic antidepressants (TCAs). Evidence for other phenotypes is considerably more limited. The CYP2D6 PM phenotype may be associated with risperidone ADRs and discontinuation due to ADRs. Venlafaxine, aripiprazole, duloxetine, and atomoxetine are newer drugs metabolized by CYP2D6 but studies of the clinical relevance of CYP2D6 genotypes are needed. Non-psychiatric drugs metabolized by CYP2D6 include metoprolol, tamoxifen, and codeine-like drugs. CYP2C19 PMs (3-4% of Caucasians and African Americans, and 14-21% of Asians) may require dose adjustment for some TCAs, moclobemide, and citalopram. Other drugs metabolized by CYP2C19 are diazepam and omeprazole. The future of pharmacogenetics depends on the ability to overcome serious obstacles, including the difficulties of conducting and publishing studies in light of resistance from grant agencies, pharmaceutical companies, and some scientific reviewers. Assuming more studies are published, pharmacogenetic clinical applications may be compromised by economic factors and the lack of physician education. The combination of a US FDA-approved test, such as the AmpliChip CYP450 Test, and an FDA definition of CYP2D6 as a 'valid biomarker' makes CYP2D6 genotyping a prime candidate to be the first successful pharmacogenetic test in the clinical environment. One can use microarray technology to test for hundreds of single nucleotide polymorphisms (SNPs) but, taking into account the difficulties for single gene approaches such as CYP2D6, it is unlikely that very complex pharmacogenetic approaches will reach the clinical market in the next 5-10 years.

Alleles↗
PubMed2006

A poor metabolizer for cytochromes P450 2D6 and 2C19: a case report on antidepressant treatment.

Scientific literature has never described a poor metabolizer for both the cytochrome P450 (CYP) 2D6 and the CYP 2C19. They are expected to be rare (<1% in different ethnic groups) and prone to adverse drug reactions with many antidepressants. In an ongoing pharmacogenetic study, after genotyping 1,576 subjects in three Kentucky state hospitals we have found one poor metabolizer for both CYP 2D6 and CYP 2C19, which corresponds to a prevalence of 0.06% (95% CI 0.01 to 0.36). The naturalistic antidepressant treatment of this poor metabolizer for both enzymes is described in this article. As genotyping reaches clinical practice, it will be interesting to prospectively establish whether mirtazapine is a reasonable choice as an antidepressant for these patients, as the data and this case suggest.

Antidepressive Agents↗
PubMed2006

AmpliChip CYP450 test: personalized medicine has arrived in psychiatry.

The US FDA has granted market approval for the first pharmacogenetic test using a DNA microarray, the AmpliChip CYP450, which genotypes cytochrome P450 (CYP)2D6 and CYP2C19. The test uses software to predict phenotypes and tests for 27 CYP2D6 alleles, including the deletions and duplications, and three CYP2C19 alleles. Other DNA microarray platforms are being developed for CYP testing, but none have been completely developed or approved by the FDA to date. The differences between an implementation of pharmacogenetic tests centered on the individual and implementation using a public health approach are discussed. In this review, the major obstacles to the wide implementation of pharmacogenetic testing in the clinical environment are summarized.

Alleles↗
PubMed2006

Probable association between ziprasidone and worsening hypertension.

According to premarketing studies, at least 1% of ziprasidone-treated patients exhibited hypertension; however, this figure is not necessarily attributable to the drug. A PubMed/MEDLINE search yielded no articles describing hypertension as a possible adverse event associated with oral ziprasidone therapy. We describe a 53-year-old African-American woman with hypertension and schizophrenia whose blood pressure increased during ziprasidone therapy. She experienced no similar blood pressure increases during therapy with four other atypical antipsychotics. Her mean systolic blood pressure during ziprasidone treatment (158 mm Hg) was significantly higher than before (141 mm Hg) and after (135 mm Hg) treatment. Also, her mean diastolic blood pressure during ziprasidone treatment (88 mm Hg) was significantly higher than after treatment (79 mm Hg). Linear regression analysis demonstrated that the patient's systolic blood pressure increased significantly with ziprasidone dose (regression coefficient [B] = 0.22 mm Hg x day/mg, 95% confidence interval 0.10-0.34, p=0.001). Thus, after adjusting for the effect of antihypertensive doses, an increase of 40 mg/day in ziprasidone yielded an increase of 8.8 mm Hg in systolic blood pressure. For unknown (perhaps genetic) reasons, this patient may have been particularly sensitive to ziprasidone. Clinicians prescribing ziprasidone in patients with hypertension should be aware that their hypertension could worsen with the addition of ziprasidone. If this occurs, replacement of ziprasidone with a different antipsychotic should be considered.

Antipsychotic Agents↗
PubMed2006

A pilot study on differences in aggression in New York City and Madrid, Spain, and their possible impact on suicidal behavior.

OBJECTIVE: Published results from a U.S. study of depressed suicide attempters and a Madrid, Spain, study including all consecutively admitted suicide attempters suggested that aggression scores were higher in U.S. attempters. This observation led us to compare depressed attempters and controls from both suicide research centers and explore whether New York City (NYC) patients carry out suicidal acts of greater lethality than patients in Madrid. The study goals were (1) to compare aggression scores in attempters and healthy volunteers between the 2 cities and (2) to determine whether higher aggression scores are associated with greater medical lethality of suicide attempts. METHOD: The respective samples from NYC and Madrid included attempters with a DSM-IV diagnosis of major depressive disorder (N = 117 and N = 133) and healthy controls (N = 90 and N = 317). Aggression scores, measured by the Brown-Goodwin Scale, in attempters and healthy volunteers from both sites were compared using an analysis of variance model. The relationship between lethality of suicidal acts and aggression scores in attempters was assessed using logistic regression analyses. NYC subjects were recruited from 1998 to 2001, and Madrid subjects were selected from consecutive admissions in 1999. RESULTS: Depressed suicide attempters from NYC made attempts of greater lethality and reported more lifetime aggressive behavior than depressed attempters in Madrid. NYC healthy volunteers also reported more aggression than their Madrid counterparts. CONCLUSIONS: This pilot study suggests that the greater lethality of suicidal behavior in NYC compared to Madrid is related to higher aggression levels, although the data have limitations. Cross-cultural studies are needed to verify whether aggression and higher lethality suicide attempts share a common diathesis explaining the higher suicide rates in NYC.

Adult↗
PubMed2006

Using data mining to explore complex clinical decisions: A study of hospitalization after a suicide attempt.

BACKGROUND: Medical education is moving toward developing guidelines using the evidence-based approach; however, controlled data are missing for answering complex treatment decisions such as those made during suicide attempts. A new set of statistical techniques called data mining (or machine learning) is being used by different industries to explore complex databases and can be used to explore large clinical databases. METHOD: The study goal was to reanalyze, using data mining techniques, a published study of which variables predicted psychiatrists' decisions to hospitalize in 509 suicide attempters over the age of 18 years who were assessed in the emergency department. Patients were recruited for the study between 1996 and 1998. Traditional multivariate statistics were compared with data mining techniques to determine variables predicting hospitalization. RESULTS: Five analyses done by psychiatric researchers using traditional statistical techniques classified 72% to 88% of patients correctly. The model developed by researchers with no psychiatric knowledge and employing data mining techniques used 5 variables (drug consumption during the attempt, relief that the attempt was not effective, lack of family support, being a housewife, and family history of suicide attempts) and classified 99% of patients correctly (99% sensitivity and 100% specificity). CONCLUSIONS: This reanalysis of a published study fundamentally tries to make the point that these new multivariate techniques, called data mining, can be used to study large clinical databases in psychiatry. Data mining techniques may be used to explore important treatment questions and outcomes in large clinical databases and to help develop guidelines for problems where controlled data are difficult to obtain. New opportunities for good clinical research may be developed by using data mining analyses.

Adult↗
PubMed2005

Guidelines for the use of clozapine in individuals with developmental disabilities.

Clozapine is the most effective antipsychotic medication currently in use, but there has been a paucity of well-controlled research on its efficacy with people with developmental disabilities. We present a set of guidelines to ensure proper utilization of clozapine in individuals with developmental disabilities, because it can offer them therapeutic advantages similar to those observed in people with schizophrenia. We provide recommendations regarding the use of clozapine that are based on three main sources: literature and published professional practice guidelines regarding the use of clozapine in individuals who do not have developmental disabilities, the limited literature on the use of clozapine in individuals who have developmental disabilities, and our own clinical experience. The first part of the guidelines contains an overview of necessary practical knowledge regarding side effects, dose and blood level considerations, and interactions with other medications, diet and tobacco smoking. In the second part, we offer procedures for selecting individuals for clozapine therapy based on proper indications and contraindications for treatment. We also include requirements regarding informed consent, dosage and special laboratory and clinical monitoring.

Adult↗