Graduate Student Research ~ Selected Abstracts

Alicia Lofgren, MS, August 2014

Asthma affects one out of eleven people in the United States and its prevalence is increasing at an average of 2.9% each year. The quintessential triad of asthmatic indicators includes airway inflammation, bronchospasm, and hypersecretion of mucus. The current treatment guidelines, as stated by the National Asthma Education and Prevention Program, call for a step-wise management system beginning with the use of inhaled corticosteroids in increasing doses. When the diseases progresses addition of long-acting β2-agonists may be necessary. Short-acting β2-agonists are used as rescue therapy when symptoms are present regardless of the stage of the disease. Systemic corticosteroids (intravenous and oral) are typically reserved for acute events, also known as exacerbations. While the currently available treatments are effective for the majority of patients, daily use is needed and side effects do occur. The primary objective of this capstone project was to review the published literature to determine how immunomodulation could improve the treatment of asthma. The specific aims were to: a) review the role of the immune system in asthmatic exacerbations; b) review approved and investigational antibody treatments for asthma and compare them with the gold standard of care. To accomplish this, a comprehensive literature review was carried out using various databases spanning the period of 1993 to the present. The National Center for Biotechnology Information databases, including PubMed and PubMed Health, as well as any resources from Google Scholar and the websites of the National Institute of Health and the U.S. Food and Drug Administration were utilized. Keywords used included asthma, asthma exacerbation, asthma treatment, monoclonal antibody therapy, anti-interleukin, anti-immunoglobulin, anti-thymocyte globulin, anti-lymphocyte globulin, anti-IL-4, anti-IL-5, anti-IL-9, anti-IL-13, anti-IL-17, anti-IgE, anti-TH2, and inflammatory cytokines.

Therapies found included anti-immunoglobulin E (IgE), which has been approved for use in the United States since 2003, anti-interleukin(IL)-5,-4,-13,-9,-17,-1β, anti-tumor necrosis factor(TNF)-α, and anti-C5 complement protein, which are currently under investigation in asthma and other allergic conditions. All treatments are primarily given as injections, subcutaneously or intravenously on a monthly or bimonthly basis. Omalizumab, marketed as Xolair®, is a recombinant DNA-derived humanized IgG1k monoclonal antibody that binds to free human IgE in the blood. It has shown statistically significant increases in lung function and quality of life scores in addition to significant decreases in exacerbations, emergency room visits, and immune cells present in the serum. Efficacy has been exhibited in patients with both allergic and non-allergic asthma, although treatment with omalizumab in allergic displays a steroid-sparing effects, allowing patients to decrease maintenance medication and experience persistent benefits of treatment for up to a year after injections have ceased. Increased flexibility in patient eligibility requirements need to be researched as numerous case reports show clinical improvements outside the recommended parameter ranges. Anti-IL-5, anti-IL-4 and anti-IL-13 treatments have shown promise in allergic asthma; however, the results have not been consistently reproducible and more work is needed to identify optimal patient pools. For the 10% of patients with refractory or difficult to treat patients, immunomodulation therapy may be indicated due to its persistency of benefit and ability to reduce or withdraw the need for daily corticosteroid therapy, thereby increasing control of a patient’s asthma while decreasing exacerbations.

Saif Alharthy, MS, May 2014

Endocrine disrupting chemicals are a group of exogenous compounds which disrupt the endocrine functions of human and wildlife. This disruption might be in the synthesis, storage, release, and actions of specific hormones. Endocrine disrupting chemicals encompass a variety of chemical classes including drugs, compounds used in plastic consumer products manufacturing, pollutants, insecticides, herbicides, and even naturally-occurring botanical products like phytoestrogens. Most of these disrupters produce estrogenic properties because of having structural similarity to endogenous 17-beta estradiol. Mimicking estradiol, they can interfere with its actions resulting in the development of several diseases, such as nervous system, diabetes, obesity, breast cancers, and reproductive impairments. One of the endocrine disrupting chemicals of most interest is bisphenol A.
Bisphenol A is a carbon-based synthetic compound and it is used in epoxy resins, polycarbonate plastics, fungicides, antioxidants, stabilizers in rubber, and as a component of dental sealants. Numerous studies have found that bisphenol A may accidentally leak into canned foods or plastic bottled drinks ingested by humans. Studies indicate that bisphenol A effects are due to its estrogenic activity and the ability to bind and activate the estrogen receptor specifically. A growing number of studies have indicated that bisphenol A might be responsible for reduction in sperm count, spermatogenesis, aromatase, seminal fluid, 17 beta hydroxysteroid dehydrogenase activity, and testosterone biosynthesis. The primary objective of this capstone project is to review the available literature in order to determine the mechanism of bisphenol A on testosterone biosynthesis. The working hypothesis was that bisphenol A induced reduction in testosterone production may be due predominantly to inhibition of 17 beta beta hydroxysteroid dehydrogenase rather than an increase in aromatase enzyme activity. This study had the following specific aims: 1) review the sex steroid biosynthesis pathway, 2) review the endocrine disrupting chemicals; 3) determine a mechanism by which the estrogen mimics BPA and affects testosterone synthesis. Literature review was conducted using the databases PubMed, Ovid Medline, CINAHL Plus, as well as the search engine Google Scholar for the period 1940 to present. The keywords used: Bisphenol A, Testosterone, Luteinizing Hormone, 17-beta hydroxysteriod dehydrogenase enzymes. It was found that human studies were limited to urine measurements in which increased bisphenol A correlated with decreased sperm account and seminal fluid volume. In animal studies, bisphenol A reduced testosterone production by direct action on the leydig cells. In the ovarian granulosa cells, bisphenol A reduced aromatase enzyme activity but unlikely to be the method, in the testes as, a decrease in aromatase activity would cause an increase in testosterone level. Since bisphenol A causes significant decrease in testosterone biosynthesis, this suggests that the inhibition in 17-beta hydroxysteroid dehydrogenase, the enzyme that converts androstenedione to testosterone, is probably the principal target for bisphenol A. In conclusion, the literature supports a strong threat from bisphenol A on male reproductive function and every effort must be taken seriously to reduce the exposure of male to this endocrine disrupting chemical.

Rocio Avila, MS, December 2013

Opioids and opiates (alkaloids found naturally in the Opium plant) are responsible for the most emergency room visits in the United States. According to the Centers for Disease Control and Prevention they are the most commonly abused medications, leading to a 300% increase in overdose deaths in the most recent decade. Opioids such as hydromorphone and codeine are schedule II drugs that have therapeutic uses but the potential for abuse and addiction is large. People may take these prescriptions for pain management, but long term use can lead to dependence. The United States Armed Forces has a zero-tolerance policy on drug abuse and The Substance Abuse and Mental Health Services Administration establishes guidelines for the federal workplace drug testing programs as well as the cutoff concentration limits for initial screen testing and confirmatory tests for making the determination of a positive sample. Gas chromatography coupled with mass spectrometry, an important and widely used analytical technique, has been heralded as the gold standard for scientific analysis, and used for such confirmatory tests. As of May 2011, the Air Force Drug Testing Laboratory expanded its opioid testing to include hydrocodone and hydromorphone and validated the method, but co-eluting peaks in the hydrocodone, hydromorphone, and codeine assay were observed during actual sample analysis. Approximately 1- 3 % of samples that may possibly be positive are reported as “unfit for testing.” The primary aim of this project was to find alternative ion fragments to use as part of the assay to reprocess problematic samples that would normally result in interferences within the ion fragments that are currently monitored in the hydrocodone, hydromorphone, and codeine gas chromatography-mass spectrometry. This assay will result in better resolution of chromatography peaks, and maintain an efficient turnaround time for reporting positive test results that meet and/or exceed Department of Defense standards. Other aims of this study were to (a) analyze urine samples that have been previously confirmed presumptive positive, but unfit for testing and with the use of the method developed in this study, demonstrate the method’s selectivity and efficient quantitation range and (b) to identify the structure of the ion fragments causing co-eluting peaks and if possible determine if their origins are from the drug taken by a person or from the fragmentation process of the gas chromatography-mass spectrometry. Samples were extracted and derivatized using a previously established method; samples were then analyzed using a gas chromatography-mass spectrometry instrument using Chemstation Drug Analysis software. Alternate ions selected for validation were as follows: hydrocodone m/z 271 and 329, the hydromorphone hexadeuterated internal standard m/z 376, and codeine ion m/z 356. Validation studies included precision, linearity, limits of detection and quantification, and upper limits of linearity and interference studies which were within the acceptable ranges established by the Armed Forces Medical Examiner System. During the interference studies, it was found that 6-acetylcodeine was being converted to codeine, and heroin and 6-acetylmorphine were converted to morphine by the hydrolysis step during sample preparation. Although these drugs interfere with the Gas Chromatography-Mass Spectrometry assay, they are markers for heroin use. It was also found that mono-esterified morphine was the cause of the interference in the codeine assay, and that using dimethylaminopyridine as a derivatizing catalyst allowed the reaction to occur rapidly thus removing the interference. Using a different catalyst to derivatize samples helped resolve co-eluting interference peaks, resulting in better resolved chromatography peaks using alternative ion fragments thus maintaining an efficient turnaround time for reporting positive test results. It is hoped that these new assay techniques will improve the testing efficiency of the Air Force Drug Testing Laboratory at Lackland AFB, TX.

Ashley Ann Johnson, MS, May 2013

Metabolic syndrome is a term used to describe a cluster of closely associated disease states that includes: hyperinsulinemia, dyslipidemia, obesity, type 2 diabetes mellitus, hypertension, platelet hypersensitivity, nonalcoholic fatty liver disease and renal dysfunction. Insulin resistance appears to be the common trait for most of the diseases but the biochemical compound that connects them has yet to be identified. The primary objective of this capstone project was to review available literature to determine if defects in the arachidonic acid metabolic pathways could possibly explain the development of the various metabolic defects commonly associated with the metabolic syndrome. This study had the following specific aims: a) review the biochemical basis of the disease states associated with metabolic syndrome; b) review metabolism of arachidonic acid and its metabolites and their role in causing the various diseases. An extensive literature review was conducted using the databases PubMed, Ovid Medline, CINAHL Plus, as well as the search engine Google Scholar. The following keywords were used alone and in combination: metabolic syndrome, insulin resistance syndrome, insulin resistance, hyperinsulinemia, dyslipidemia, obesity, type 2 diabetes mellitus, hypercoagulation, platelet hypersensitivity, hypertension, blood pressure regulation, renal dysfunction, renal damage, proteinuria, cardiovascular disease, arachidonic acid, phospholipase A2, cyclooxygenase, lipoxygenase, epoxygenase, hydroxylase, isoprostane, prostaglandin, thromboxane, prostacyclin, leukotriene, lipoxin, hydroxyeicosatetraenoic acid, epoxyeicosatrienoic acid, and platelet activating factor.

Insulin secretion has been shown to be stimulated by increased arachidonic acid in obese rodents and human pancreatic β cells explaining the development of hyperinsulinemia. Dyslipidemia, increased low-density lipoprotein, triglycerides, and decreased high-density lipoprotein, may be related to increased concentrations of prostaglandin E2, shown in male Wistar rats to reduce glycerol release and therefore reduce lipolysis. The presence of increased levels of 12-hydroxyeicosatetraenoic acid, prostaglandin E2, thromboxane A2, leukotrienes, and isoprostane, as seen in obese animal models and diabetic subjects, are correlated with increased levels of tumor necrosis factor alpha and interleukin 6 cytokines and may account for the defects observed in obesity and type 2 diabetes mellitus. Platelet hypersensitivity may be produced by increased agonists of platelet aggregation: prostaglandin E2, thromboxane A2, and isoprostanes, as shown in experimental studies. In hypertension, increased levels of 20-hydroxyeicosatetraenoic acid, thromboxane A2, isoprostanes, 12-hydroxyeicosatetraenoic acid, which stimulate vasodilation and aldosterone release, and decreased levels of platelet activating factor, vasodilator, may account for the elevated blood pressure. Arachidonic acid metabolites that are anti-inflammatory inhibit platelet aggregation, and promote vasodilation are decreased in the previously mentioned disease states. Renal dysfunction, evidenced by proteinuria is significantly correlated with increased cytochrome 4A hydroxylase and cyclooxygenase activity and decreased cytochrome 2C epoxygenase activity. Nonalcoholic fatty liver disease in obese rodent models and humans has been shown to have increased levels of tumor necrosis factor alpha, lipoxygenase enzymes and products. Arachidonic acid metabolic enzymes 5-, 12-, and 15-lipoxygenase, cyclooxygenase-2, and cytochrome 4A hydroxylase have been shown to be increased in experimental models. Also found to be increased in both animal and human experiments was secretory phospholipase A2 group IIA which has been shown to release arachidonic acid preferentially to the cyclooxygenase pathway and be induced by 12-/15-lipoxygenase activity. Together, there appears to be credible evidence that arachidonic acid metabolism may play a significant role in the development of several of the diseases associated with the metabolic syndrome. The activity of 12/15-lipoxygenase enzyme is of particular interest. Future research is should examine arachidonic acid metabolite and enzyme levels in the plasma, adipose, pancreatic, renal, and hepatic concentrations in human subjects. Genetic studies of polymorphisms in these enzymes may also be beneficial.

Victor Trejo, Jr., MS, May 2013

The use of “Bath salts” a cohort of synthetic stimulants, has recently increased in popularity due to its increased exposure in the media, perceived legality of such substances and because of the decreasing purity of other stimulants such as cocaine, ecstasy, and amphetamines. Recently, governments around the world, particularly the United States and the United Kingdom, have banned such synthetic stimulants. Mephedrone and methylenedioxypyrovalerone are two examples of bath salts and as their popularity have increased so have the number of cases presenting with bath salt intoxications. Bath salts are a relatively novel recreational drug derived from the Khat plant (Catha Edulis) and are categorized as beta-keto-amphetamines, yet users have reported feeling physiological symptoms similar to those felt with classical stimulants. The primary objective of this capstone project was to, review the literature for the mechanism of action and pharmacology of classical drugs of abuse, namely, cocaine, ecstasy and methamphetamine, evaluate the clinical symptoms observed with bath salt use and determine which known toxidromes they are consistent with. Proposing a possible toxidrome to identify mephedrone toxicity based on this information may be helpful in providing treatment.

A systematic literature search was carried out using various databases including PubMed and Ovid Medline over a period of 2007-2013, on the classical stimulant drugs of abuse using key words, mephedrone, cocaine, ecstasy, and amphetamine. Sciverse Science Direct (2007-2013) was used with the keywords forensic cases, mephedrone, toxicity, reported deaths, blood concentrations, United States, Europe, and UK. Scifinder Scholar was also used with the keywords that were used in this search were in-vitro, in-vivo, mice, rats, dopamine, serotonin, norepinephrine, cocaine, amphetamines, ecstasy, pharmacology, mechanism of action, brain, physiological, and clinical symptoms.

In vitro and In vivo rat studies revealed that mephedrone acted as a weak blocker of the uptake of dopamine, norepinephrine, and serotonin. It was a less potent uptake blocker than cocaine but was a potent enhancer of the release of these neurotransmitters similar to amphetamines and ecstasy via reverse transport. It is this massive release of neurotransmitters that elicit several effects such as euphoria, increased energy, empathy, hallucinations, and tachycardia reported by several users. Several case reports have begun to be reported indicating that many mephedrone users exhibit many of the desired effects of the drug, but also erratic and dangerous behavior. These symptoms could also be caused by other stimulants, like cocaine, amphetamines, and ecstasy. This could make identifying what drug may be behind the symptoms difficult and it is imperative that as much information surrounding the patient’s actions prior to arriving to the ER, witness accounts, and any additional information from Emergency Medical Services is taken into consideration before determining treatment. Treatment for mephedrone toxicity is mainly supportive and similar to that given for other stimulants and may consist of a variety of benzodiazepines, gastric lavage, and antipsychotics. As with any novel synthetic drug, its detection in biological fluids poses challenges because it is not detectible using current colorimetric or immunological screen tests or may give false positives for other drugs. Mephedrone has been detected using Gas Chromatography/Mass Spectrometry and Liquid Chromatography/Tandem Mass Spectrometry but without increased awareness of the drug’s effects and analytical procedures used to confirm them, there is a risk that mephedrone can be overlooked or cases can be improperly classified. Currently, there is no toxic concentration range for mephedrone and the reported range at which fatalities have occurred varies widely, so additional toxicological analysis data needs to be collected.

Mary Heinrich Rolf, MS, December 2012

The desire for the use of “natural” remedies over the past three decades has led to increased demand for several relatively new dietary supplements. However some, such as Ginkgo biloba extract, have been a mainstay for thousands of years initially used within the Chinese culture as an herbal remedy where the trees were discovered. Several parts of these trees have been extracted and used as dietary supplements to enhance memory and blood flow. Through scientific studies Ginkgo biloba extract or EGb has been shown to reduce platelet aggregation in vitro, although the underlying mechanisms of action are not fully understood especially after oral ingestion. The primary objective of this pilot study was to elucidate the underlying mechanism of platelet activating factor (1-O-alkyl-2-acetyl-sn-glycerol-3-phosphorylcholine)-induced in vitro platelet aggregation using ginkgolide A (GA) and ginkgolide B (GB), which are present in the terpene fraction of the Ginkgo biloba extract and are known to be specific PAF receptor antagonists. The driving hypothesis was that these terpenes contributed to the inhibition of platelet aggregation by inhibiting TXA2 production. Specimens stored at -86°C were from Dr. George Kudolo’s Ginkgo biloba research performed at the University of Texas-Health Science Center at San Antonio from 2002 through 2004. Platelet-rich plasma harvested from three healthy controls and three Type 2 diabetic subjects after ingesting placebo or Ginkgo biloba extract (120 mg daily as a single dose) for 3 months were selected. In vitro platelet aggregation studies were performed for 5 minutes using PAF alone or after pre- incubation with 8 µM GA, 8µM GB or 10 µM EGb for one minute. Expressing the data from the three subjects as the minimum, median, and maximum, comparisons were made between the plasma immunoreactive thromboxane B2 (TXB2), a metabolite of TXA2, between the placebo and Ginkgo biloba extract cycles and between the healthy and diabetic subjects. For the healthy individuals, there was a significant inhibition of PAF-induced TXB2 production when the platelets harvested from both the placebo and Ginkgo biloba extract cycles were pre-incubated with EGb. GA and GB were able to inhibit TXB2 production after the ingestion of Ginkgo biloba extract capsules but were unable to inhibit TXB2 production after the ingestion of the placebo. For the diabetic subjects, PAF-induced TXB2 inhibition was only observed when the platelets for both the placebo and Ginkgo biloba extract cycles were pre-incubated with EGb. Neither GA nor GB was able to demonstrate inhibition of TXB2 production in either cycle.

Urine samples for 6 subjects with and without diabetes were analyzed for 11-dehydrothromboxane B2 (11-dehydroTXB2), the metabolite of TXB2, as a marker for whole body platelet activity. As expected, the ingestion of Ginkgo biloba extract exhibited a decrease for 5 of the 6 healthy subjects in urinary 11-dehydroTXB2 levels excretion. The diabetic subjects did not show consistent results as half of the subjects showed an increase while the other half showed a decrease in 11-dehydroTXB2 rate.

The results of this small sample size project showed that PAF does stimulate platelet TXA2 production and this is receptor mediated as urinary 11-dehydroTXB2 excretion was reduced after ingestion of Ginkgo biloba extract in the healthy subjects with no significant difference in the diabetic subjects. This could be due to the fact that diabetic subjects usually have very hyperactive platelets and perhaps a larger dose than 120 mg/day may be required.

Leia Lozano, MS, December 2012

Green tea (Camellia sinensis) is a popular beverage worldwide that has been associated with health benefits throughout centuries. The potential health benefits have been attributed to the chemical composition of the beverage which is supported by in vitro (animal and human cell lines) and animal studies. However the health benefits of green tea may not be possible in human beings without consuming large doses. This may result in toxicity directly or indirectly by modulating cytochrome enzyme metabolism of therapeutic alkaline drugs. The primary objective of this capstone project is to review the literature on the health benefits green tea consumption and the possible toxicity when consumed with alkaline drugs. A systematic search using PubMed, Ovid, AltHealthWatch, Toxnet, and Micromedex databases was conducted using the keywords: green tea, catechins, epigallocatechin-3-gallate and Camellia sinensis combined with hepatoxicity, metabolism, CYP450, cardiovascular, diabetes, cancer, prostate and breast cancer, benzodiazepines, and anti-psychotic drugs. Several in vitro and animal studies with green tea exhibited chemopreventive and beneficial cardiovascular properties. Green tea extract has been shown to decrease glucose levels in vitro by inhibiting sodium dependent glucose transporters and glycogen phosphorylase and reduce plasma cholesterol by altering low density lipoprotein transport in animal studies. This suggests that green tea might have a possible role in the management of blood glucose in diabetes and high blood cholesterol. However, these expectations have not been supported by human clinical trials. It would appear that higher doses of green tea may be needed to produce an effect in humans. Regarding cancer, the extract has been shown to modulate the cell cycle by inducing apoptosis. With hormone dependent cancers such as prostate cancer, epigallocatechin-3-gallate, a dominant active ingredient in green tea, shown to lower circulating levels of testosterone in animal studies which may indicate chemopreventive properties, and to induce apoptosis in androgen independent prostate cancer. In estrogen sensitive breast cancer studies, green tea was reported to enhance the effect of the estrogen antagonist tamoxifen in vitro and in animal studies, and induction of apoptosis in MCF-7 cancer cell line. These reported health benefits have increased the notoriety of this beverage and dietary supplement prompting increased consumption and increased dosages of the supplements. However, increased consumptions in order to benefit from green tea may lead to toxicity. Several case reports are available indicating that green tea supplements may be toxic when consumed alone or concurrently with medications. Consumption of green tea has been found to interact with several medications, including warfarin, clozapine and amolodipine. These interactions and toxicity were mainly due to upregulation of cytochrome enzymes 1A2 and 3A4. Future studies are necessary to determine the effect of green tea on other variants of the cytochrome enzyme system and the effect of the concurrent consumption of green tea and other classes of drugs. Future human clinical trials with a diverse population comparing green tea supplements and purified catechin forms are also necessary to determine health benefit claims.

Meredith Murrell, MS. May 2012

Major depressive disorder, a disabling mood disorder, is thought to be caused by a variety of genetic, environmental, psychological, and biochemical factors. The biochemical factors may involve the monoamine neurotransmitters, serotonin and norepinephrine. Various antidepressant drugs from different drug classes are prescribed to modulate these neurotransmitters. These classes include selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors, tricyclic antidepressants, and monoamine oxidase inhibitors. Venlafaxine (Effexor®), a serotonin-norepinephrine reuptake inhibitor, exerts its antidepressant effects by inhibition of serotonin and norepinephrine transporters, the predominant inhibition effect being on the serotonin transporters.

Venlafaxine can cause adverse effects such as nausea, dizziness, constipation, and fatigue at therapeutic concentrations and seizures and central nervous system depression in overdose. Studies have been conducted examining venlafaxine toxicity in fatalities where venlafaxine was involved in the cause of death. These studies have examined the postmortem distribution of venlafaxine in blood, bile, vitreous humor, kidney, and liver; however there is little research examining how venlafaxine is distributed in the brain and how brain concentrations are related to blood venlafaxine concentrations. The goals of this study were to: a) measure the amount of venlafaxine and its metabolite O-desmethylvenlafaxine in extracts of temporal lobe, occipital lobe, and cerebellum; b) determine if increased concentrations of venlafaxine in femoral blood leads to increased concentrations in the brain. The driving hypothesis was that the concentration of venlafaxine would be disproportionately distributed among regions of the human brain, with regions known to possess higher amounts of serotonin transporter and norepinephrine transporter accumulating higher amounts of drug; furthermore, higher brain venlafaxine levels would be found in decedents with higher postmortem blood venlafaxine levels.

Brain samples were collected by the Southwest Brain Bank of the University of Texas Health Science Center San Antonio (San Antonio, Texas). Brain extracts were prepared from six subjects whose postmortem toxicology report revealed detectable venlafaxine amounts in femoral blood samples (amounts ranged from 0.3- 1.1 µg/ml) and one control subject in whom no drugs were detected in the blood. Blood venlafaxine concentration was determined by gas chromatography and mass spectrometry. Venlafaxine concentrations, in the brain extracts, measured by high pressure liquid chromatography and ultraviolet detection, were 1.439 ±0.412, 1.201 ±0.322, and 0.922 ±0.265 (µg/g) for temporal lobe, occipital lobe, and cerebellum, respectively. O-desmethylvenlafaxine concentrations were 1.409 ±0.362, 1.523 ±0.305, 0.272 ±0.281 ( µg/g), respectively. The ratio of O-desmethylvenlafaxine/venlafaxine was calculated for each subject as a relative measure of drug metabolism within each region (higher ratios indicated a greater conversion of venlafaxine to O-desmethylvenlafaxine); the ratios were 1.056 ±0.502, 1.368 ±0.587, and 0.400 ±0.595 for temporal lobe, occipital lobe, and cerebellum, respectively. Examining venlafaxine, O-desmethylvenlafaxine, and O-desmethylvenlafaxine/ venlafaxine across the brain regions, venlafaxine levels were nearly significant (p=0.056), O-desmethylvenlafaxine levels were different (p=0.006), and O-desmethylvenlafaxine/venlafaxine ratios were different (p=0.027). The temporal lobe had the highest venlafaxine concentrations and together, with the occipital lobe, the greatest amount of O-desmethylvenlafaxine. Using Pearson correlation tests, venlafaxine concentrations were compared to blood results and cerebellum was the only region that had a significant correlation. This study indicated that venlafaxine and O-desmethylvenlafaxine are differentially distributed throughout the postmortem human brain and that higher levels of venlafaxine in postmortem blood led to higher levels of drug accumulation in the brain. The recognized higher expression of serotonin transporter and cytochrome P450 2D6 in temporal lobe compared to cerebellum may explain the differences observed in different parts of the brain. The major limitation of this study was the small sample size and small number of brain regions examined. Future studies should consider examining more brain regions with more subjects and possibly examining more antidepressant drugs.