Biologic Therapies and Psychopharmacology Overview

Biologic Therapies
33.1 Preface

  • The section on Biologic Therapies is organized in a pharmacologically driven order, aligned with the Neuroscience-based Nomenclature (NbN).

  • The arrangement consists of 21 subsections focused on pharmacologic domains (e.g., neurotransmitters) and modes of action (e.g., antagonists, reuptake inhibitors).

  • Examples:

     - Risperidone categorized under "dopamine blockers" as a "dopamine-serotonin antagonist."
     - Previous categorization of “antidepressants” now has clomipramine and bupropion reclassified as “monoamine enhancers.”

  • Chapters addressing unique indications or combinations of different mechanisms remain indication-driven.

  • An "NbN ID" has been assigned to drugs throughout the section to clarify main neurobiologic properties.

  • Includes new agents like esketamine and pimavanserin and a global perspective on biological therapies across continents.

  • Focus on gender and sex differences in psychopharmacological treatment and exploration of novel fast-acting treatments (e.g., MDMA, psilocybin).

33.1a General Principles of Psychopharmacology

  • Definition: Psychopharmacology involves the use of medications to treat mental disorders.

  • History:

     - The first edition of Kaplan and Sadock’s Comprehensive Textbook of Psychiatry (1967) noted the emergence of psychotropic medications.

     - Drugs included:
         - Chlorpromazine (Thorazine) recognized for its therapeutic impact in psychosis, approved by the FDA in 1954.
         - Benzodiazepines introduced in 1959 were later seen as essential in psychiatric care despite initial minor classification.
         - Lithium (Eskalith), perceived ineffective until later recognized as standard treatment for mania.

  • Evolution: The development of psychopharmacology has challenged psychoanalytic movements, leading to a heightened significance of drug treatments.

  • Current Crisis: High failure rates in drug trials, limiting development of innovative psychiatric drugs.

     - Newer FDA medications include esketamine, brexanolone, and lumateperone for treatment-resistant depression, postpartum depression, and schizophrenia.
     - Urges the understanding of psychopharmacology principles, emphasizing the basics of pharmacology to better comprehend psychiatric medications.

Receptor Pharmacology

  • General Mechanism: Drugs used to palliate psychiatric symptoms act upon neurotransmitters by mimicking, blocking, or modifying their actions.

     - Receptors of interest are typically transmembrane molecules, encountered as either ionotropic or metabotropic types (G-protein coupled).

  • Receptors Info:

     - Various neurotransmitters such as acetylcholine, glutamate, GABA, and serotonin are highlighted as agonists of these receptors.

Receptor Analysis

  1. Mechanisms for Studying Receptors:

     - Binding Assays: Measure ligand (often labeled with radioactivity) binding capabilities to membranes from cultured cells/brain tissue.

         - This can determine receptor quantity and affinity.
         - Protocol includes competitive/nonradioactive ligand binding and scintillation spectrometry.
         - Biologic (Efficacy) Assays: Measures physiological responses to agonists (like organ strips) post-agonist binding.

Figures and Computational Analysis of Receptor Binding:

  • Figure 33.1a–1: Demonstrates binding kinetics of ligands, distinguishing specific from non-specific binding.

  • Figure 33.1a–2: Charts Scatchard and Hill plots for receptor analysis.

Structure and Function of Receptors

  • Ionotropic and Metabotropic Receptors:

     - Ionotropic, affected directly through ligand binding, allow ion flow.
     - G protein-coupled receptors involve secondary messengers altering cell states following agonist interactions.

G Protein Modulation of Agonist Binding

  • G protein effects illustrated via isoproterenol binding experiments with GTP.

  • Agonist affinity variability based on G protein receptor engagement.

Receptor Desensitization and Dynamics

  • Receptor desensitization affects responsiveness to continued agonist presence and involves G protein-receptor kinases (GRKs). Internalization may occur with prolonged agonist exposure.

Signaling Pathways

  1. G Proteins and Activation:

     - G proteins are pivotal in cellular processes mediated through heterotrimeric partners (Gα, Gβ, Gγ) responding to receptor activation.

  1. Second Messenger Systems:

     - cAMP productions via adenylyl cyclase – significant for future psychopharmacological insights.
     - Phospholipases aide in generating lipid messengers vital for signaling.

General Issues in Clinical Psychopharmacology

  • This section provides insight into critical aspects regarding psychotropic drugs and their clinical applications, emphasizing treatment efficacy and ethical implications of broader drug usage.

  • Noteworthy findings include patient response variabilities and developments in clinical practices that invite heightened awareness of pharmacogenetic factors.

Drug Development and Approval Process in the United States

  • This section addresses both challenges faced in psychiatric drug development and the evolution of policing and approving drugs by the FDA.

  • Key Facts:

     - Estimated development costs at $2.6 billion, with CNS drugs facing higher development hurdles.
     - The history of drug regulation is rooted in tragic events leading to safety protocols and requirements.

Phases of Drug Development

  • Phase 1: Introduces drugs to humans, assesses safety and tolerable doses.

  • Phase 2: Determines initial efficacy in target conditions, gathering important safety data.

  • Phase 3: Larger-scale trials assess efficacy versus safety ratios.

  • Phase 4: Postmarketing surveillance continues drug safety assessment.

Future Directions for Medical Approaches

  • The document outlines both emerging methods to improve psychotropic drug development and regulatory considerations within the evolving landscape of psychiatric medicine.

  • Emphasis placed on adapting clinical approaches to patient-centered care alongside exploring biomarkers and personalized treatment measures concerning effectiveness.

High Yield Notes:

  • Pharmacology Order: Understand the structured approach of pharmacologic domains for effective study strategies.

  • New Medications: Familiarize yourself with novel agents like esketamine and their indications for treatment-resistant cases.

  • Receptor Mechanisms: Focus on how receptor types play a crucial role in drug efficacy—ionotropic vs. metabotropic.

  • Clinical Implications: Be aware of ethical considerations and variability in patient responses to psychotropic treatments that can impact practice.

  • Development Phases: Knowing the stages in drug development is vital for understanding regulatory frameworks and realities of new boiological therapies.

  • Future Approaches: Stay updated on biomarkers and personalized medicine as these are key trends shaping the future of psychopharmacology.