1 GENDER DIFFERENCES IN CLINICAL RESEARCH GAUTAM CHAUDHURI, M.D., Ph.D. CARLA JANZEN, M.D. LAUREN NATHAN, M.D. BARBARA A. LEVEY, M.D. DEPARTMENTS OF OBSTETRICS AND GYNECOLOGY AND MOLECULAR AND MEDICAL PHARMACOLOGY DAVID GEFFEN SCHOOL OF MEDICINE AT UCLA

2 DEFINITIONS SEX refers to the classification of living things, generally as male or female, according to their reproductive organs and functions assigned by chromosomal complement. GENDER refers to a person’s self- representation as male or female. Gender is rooted in biology and shaped by environment and experience.

3 SEX DIFFERENCES IN RECOVERY FROM STROKE Females are more likely than males to recover language ability after suffering a left hemisphere stroke Men and women differ in brain organization for language –Men rely on left inferior frontal gyrus to carry out language tasks –Women use both the right and left inferior gyri to carry out certain language tasks

4 SEX DIFFERENCES AND DEPRESSION Female gender is a major risk of depression by 2:1 ratio Prevalence of major depression in women (21.3%) versus men (12.7%)

5 WOMEN IN CLINICAL TRIALS FDA 1977 guidelines directed that women of child- bearing potential be excluded from Phase I and early Phase II trials but women could participate later. Child bearing potential was narrowly defined as any woman physiologically capable of becoming pregnant, regardless of sexual activity, sexual practices and contraceptive use In 1990, the NIH directed that women and minorities be included in clinical trials

6 SEX DIFFERENCES Physiological factors Molecular factors

7 SEX DIFFERENCES AND CLINICAL RESEARCH The following should be considered –Genetic differences –Phase of menstrual cycle –Premenopausal vs. postmenopausal –Use of oral contraceptives or hormone replacement therapy –Pregnancy –Lactation

8 SEX DIFFERENCES Physiological factors –Generally lower Body weight Organ size Glomerular filtration rate –Generally higher Percentage of body fat –Different gastric motility in women compared to men

9 GENETIC/MOLECULAR BASIS OF SEX BASED DIFFERENCES Genetic/molecular basis of sex-based differences may be due to: –Sexual genotype –Genes on sex chromosomes may be expressed differently between males and females (single or double copies of the gene, differing meiotic effects, X chromosome inactivation, genetic imprinting) –Source of X chromosome (maternal or paternal)

10 MOLECULAR FACTORS Men seem to have higher activity relative to women for: –Cytochrome P 450 (cyp) isoenzymes Cyp 1A2 Cyp 2E1 –Drug efflux transporter P-glycoprotein Some isoforms of glucuronyl transferase and sulfotransferases Women have higher –Cyp 2D6 activity –Cyp 3A4 activity

11 PRINCIPLES OF DRUG ACTION Absorption Bioavailability Volume of distribution Plasma protein binding Action on receptor site Termination of activity –Redistribution –Metabolism –Renal excretion

12 SEX DIFFERENCES AND ANTIDEPRESSANT PHARMACOKINETICS Oral contraceptives decrease the hepatic metabolism of imipramine because of changes in hepatic blood flow Imipramine dosage reduction is necessary in chronic long-term oral contraceptive users to 2/3 rd that given to non-contraceptive users Women older than 50 years have higher plasma concentrations of amitriptyline than age matched men

13 BIOAVAILABILITY OF DRUGS Extent to which and the rate at which an administered drug dose reaches the systemic circulation unchanged Bioavailability of a drug administered intravenously is equal to unity Bioavailability of a compound administered as an oral, intramuscular, or subcutaneous formulation is assessed in relation to intravenous drug

14 HALF-LIFE OF A DRUG volume of distribution Half-life =X log c 2 clearance

15 DISTRIBUTION OF DRUGS Rate at which equilibrium between tissue and plasma concentration is achieved depends on: –Blood perfusion rate to organs –Drug lipid solubility –Drug’s ability to bind to proteins or tissues

16 LIPID SOLUBILITY AND DISTRIBUTION OF DRUGS If lipid soluble – more likely to cross biological barriers such as cell membranes, blood-brain barrier, and placenta If water soluble – will cross membranes only if it’s of small molecular size

17 DRUG METABOLISM Water soluble drugs –Eliminated unchanged after glomerular filtration Lipid-soluble drugs –Rendered more polar by metabolism prior to excretion in bile or urine –Oxidation (hydroxylation, demethylation) –Conjugation (glucoronide, sulphate)

18 PHYSIOLOGICAL CHANGES IN PREGNANCY Total body water increases - up to 8 liters Plasma volume increases by 50% Plasma albumin falls by 5-10 g/L Increase in body fat by 3-4 kg Increase in body weight Maternal cardiac output increases by 30-50% during pregnancy (4.5 l/min  6 l/min)

19 EFFECTS OF INCREASE IN CARDIAC OUTPUT Uterine circulation500 ml/min at term Effective renal plasma flowIncreased by 75% over non- pregnant levels to 891 ml/min by 26 weeks (NP – 480 ml/min) Glomerular filtration rateIncreased by 50% from 99 ml/min – non-pregnant to 152 ml/min – by 26 weeks Creatinine clearance rate ml/min

20 INFLUENCE OF PHYSIOLOGICAL CHANGES IN PREGNANCY ON DRUG HANDLING Ingestion –Compliance Fear that fetus may be harmed Nausea, vomiting and heartburn Absorption –Gastric function Delayed gastric emptying Gastric acid secretion is decreased by 40% –Functions of small intestine –GI transit is prolonged by 30-50% –Drugs if metabolized in gut wall eS chlorpromazine, may reduce bioavailability Epidural space –Greatly increased vascularity in epidural space Demerol more rapidly absorbed

21 CYTOCHROME P-450 AND SEX STEROIDS High levels of progesterone may inhibit some enzymes of P-450 system –CYP 1A2 leading to decreased elimination of theophylline, caffeine, and zileuton High levels of progesterone may increase activity of some enzymes –CYP 3A4 and CYP 2C9 leading to increase in hepatic elimination of drugs like phenytoin and sertraline

22 ANTICONVULSANTS AND PREGNANCY Phenytoin –Increased clearance resulting in lower serum concentrations –  absorption  plasma protein binding  metabolism

23 DRUG METABOLISM IN PREGNANCY CARBAMAZEPINE PHENYTOIN ARENE OXIDES (EPOXIDES) PHENOLIC COMPOUNDS HYDROLYZED CONJUGATION WITH GLUCURONIC ACID PHENOLIC COMPOUNDS CONJUGATION WITH GLUCURONIC ACID HYDROLYZED OXIDATION ARENE OXIDES (EPOXIDES)

24 ANTIBIOTIC LEVELS AFFECTED DURING PREGNANCY Ampicillin, penicillin, cefazolin levels decreased by 50% Gentamycin, tobramycin, and amikacin serum concentrations are also reduced

25 ASTHMA THERAPY AND PREGNANCY –Inhaled steroids and beta agonists commonly used –Theophylline serum concentrations can be elevated during pregnancy (  CYP 1A2)

26 CARDIOVASCULAR AGENTS AND PREGNANCY Serum concentrations of propranolol, labetalol, and atenolol not changed Lowered serum concentrations with metoprolol

27 SUBSTRATES - 1 1A22B62C192C92D62E13A4, 5, 7 amitriptyline caffeine clomipramine clozapine cyclobenzaprine (Flexeril®) estradiol fluvoxamine haloperidol imipramine N- DeMe mexiletine naproxen ondansetron phenacetin=> acetaminophen =>NAPQI propranolol riluzole ropivacaine tacrine theophylline verapamil (R)warfarin zileuton zolmitriptan bupropion cyclophosphamide ifosfamide Proton Pump Inhibitors: lansoprazole omeprazole pantoprazole E-3810 Anti-epileptics: diazepam=>Nor phenytoin(O) S-mephenytoin phenobarbitone amitriptyline citalopram clomipramine cyclophosphamide hexobarbital imipramine N-DeME indomethacin R-mephobarbital moclobemide NSAIDs: diclofenac ibuprofen meloxicam S-naproxen=>Nor piroxicam suprofen Oral Hypoglycemic Agents: tolbutamide glipizide Angiotensin II Blockers: losartan irbesartan amitriptyline celecoxib fluoxetine fluvastatin glyburide phenytoin=>4-OH Beta Blockers: carvedilol S-metoprolol propafenone timolol Antidepressants: amitriptyline clomipramine desipramine imipramine paroxetine Antipsychotics: haloperidol perphenazine risperidone=>9OH thioridazine alprenolol amphetamine bufuralol chlorpheniramine chlorpromazine Anesthetics: enflurane halothane isoflurane methoxyflurane sevoflurane acetaminophen =>NAPQI aniline benzene chlorzoxazone ethanol N,N-dimethyl formamide theophylline =>8-OH Macrolide antibiotics: clarithromycin erythromycin (not 3A5) NOT azithromycin Anti-arrhythmics: quinidine=>3-OH (not 3A5) Benzodiazepines: alprazolam diazepam=>3OH midazolam triazolam Immune Modulators: cyclosporine tacrolimus (FK506)

28 SUBSTRATES - 2 1A22B62C192C92D62E13A4, 5, 7 nelfinavir nilutamide primidone progesterone proguanil propranolol teniposide R-warfarin=>8- OH rosiglitazone tamoxifen torsemide S-warfarin codeine (=>O- desMe) debrisoquine dexfenfluramine dextromethorphan encainide flecainide fluoxetine fluvoxamine lidocaine metoclopramide methoxyamphetamine mexiletine nortriptyline minaprine ondansetron perhexiline phenacetin phenformin propranolol (=>4OH) quanoxan sparteine tamoxifen tramadol venlafaxine HIV Antivirals: indinavir nelfinavir ritonavir saquinavir Prokinetic: cisapride Antihistamines: astemizole chlorpheniramine terfenidine Calcium Channel Blockers: amlodipine diltiazem felodipine lercanidipine nifedipine nisoldipine nitrendipine verapamil

29 SUBSTRATES - 3 1A22B62C192C92D62E13A4, 5, 7 HMG CoA Reductase Inhibitors: atorvastatin cerivastatin lovastatin NOT pravastatin simvastatin Steroid 6beta-OH: estradiol hydrocortisone progesterone testosterone Miscellaneous: alfentanyl buspirone caffeine=>TMU cocaine dapsone=>N-OH codeine- N- demethylation dextromethorphan fentanyl finasteride haloperidol irinotecan LAAM lidocaine

30 SUBSTRATES - 4 1A22B62C192C92D62E13A4, 5, 7 methadone odanestron pimozide propranolol quinine salmeterol sildenafil sirolimus tamoxifen taxol terfenadine trazodone vincristine zaleplon zolpidem

31 RECOMMENDATIONS Clarify use of terms sex and gender Determine and disclose the sex of origin of biological research materials Identify endocrine status of research subjects Design studies so that results can be analyzed by sex Promote research on sex at the cellular level Encourage and support interdisciplinary research on sex differences