drugs and the brain
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Drugs and the BrainPsychotropic Medications - Effects and Adverse EffectsAdonis Sfera, MD
Neurovascular coupling
Why Do We Get Side Effects From Drugs?
The benefits of the medication will often outweigh the cost of the side effects by improving heath or allowing people to function in daily life.
It is up to us to decide.
Any time you alter you body chemistry you will have some form of side effect.
Sometimes The Risks Do Not Outweigh The Benefits
Current Psychotropic Drugs Are Not “Smart” Drugs
They travel to every area of the body including the brain
Let’s Follow the Drug
Brain Compartments
First Compartment: The Brain Vessels
Extracellular Space - Between Capilaries and Cells
Second Compartment: The Space Between The Cells
The Firewall (Blood Brain Barrier) The blood-brain barrier (BBB) is located
between the blood vessels (capilaries) and the extracellular space of the brain.
Blood Brain Barrier (BBB) Endotelial cells Astrocyte endfeet
Trans-cellular passage of drugs
Passage of drugs from the bloodstream to the brain is dependent on the ability of the molecules to penetrate through cell membranes.
Crossing the Membranes
Penetration of a molecule from the bloodstream to the neurons and glial cells is dependent on the compound's liposolubility.
Targets of psychotropic drugs
30% of psychotropic drugs target transporter proteins
30% of psychotropic drugs target G protein linked receptors
20% of psychotropic drugs target ligand-gated ion channels
10% of psychotropic drugs target voltage sensitive ion channels
10% of psychotropic drugs target enzymes
Transporter Protein and G Protein (60% of psychotropic drugs)
Stahl SM Stahl’s Essential Psychopharmacology; The Prescriber’s Guide 4th ed 2011
Ligand Gated Ion Channels, Voltage Sensitive Ion Channels and Enzymes (40% of psychotropic drugs)
Stahl SM Stahl’s Essential Psychopharmacology; The Prescriber’s Guide 4th ed 2011
Transporter ProteinsTransporters are receptors that bind neurotransmitters (they go in and out of the neuronal membrane 12x)
Stahl SM Stahl’s Essential Psychopharmacology; The Prescriber’s Guide 4th ed 2011
All Antidepressants (except MAO inhibitors) Target and Block Transporter Proteins
Serotonin Transporter(SERT); Norepinephrine Transporter(NET);Dopamine Transporter(DAT)
Antidepressants Bind to Transporters1. When Na binds to the transporter, serotonin also binds and renders the transporter ready.
2. When the antidepressantbinds to the transporter it displaces serotonin and Na, blocking the transporter
Stahl SM Stahl’s Essential Psychopharmacology; The Prescriber’s Guide 4th ed 2011
G Protein Linked ReceptorsG protein linked receptors (7 transmembrane regions, one intracellular and one extracellular portion)
Ligand-Gated Ion Channels (20% of Psychotropic Drugs)
Stahl SM Stahl’s Essential Psychopharmacology; The Prescriber’s Guide 4th ed 2011
N Methyl D Aspartate Receptors
GABA Receptors
VOLTAGE SENSITIVE CHANNELS
Voltage -sensitive sodium channels Voltage-sensitive calcium channels
Voltage-Sensitive Sodium Channels
Stahl SM Stahl’s Essential Psychopharmacology; The Prescriber’s Guide 4th ed 2011
Some Mood Stabilizers’ Binding Sites
Stahl SM Stahl’s Essential Psychopharmacology; The Prescriber’s Guide 4th ed 2011
Voltage-Sensitive Calcium Channels
Alpha 2 Delta Ligands
Antihypertensive Calcium Channel Blockers
Enzymes Directly Targeted by Psychotropic Drugs
Some Enzymes Create New Molecules.Others Destroy Existing Molecules.
Stahl SM Stahl’s Essential Psychopharmacology; The Prescriber’s Guide 4th ed 2011
Enzymes as Targets of Psychotropic Drugs
Stahl SM Stahl’s Essential Psychopharmacology; The Prescriber’s Guide 4th ed 2011
Irreversible Enzyme Inhibitor
An irreversible inhibitor of an enzyme binds to the enzyme in such a way that permanently prevents a substrate from binding.
Stahl SM Stahl’s Essential Psychopharmacology; The Prescriber’s Guide 4th ed 2011
Reversible Enzyme Inhibitor
Dopamine Pathways
I wish I could inhibit only the mesolimbic pathway, but I cannotbecause the drugs are not “smart”.
All antipsychotics (typical and atypical) are dopamine D2 blockers, butunfortunately they affect other receptors as well-adverse effects
Stahl SM Stahl’s Essential Psychopharmacology; The Prescriber’s Guide 4th ed 2011
Stahl SM Stahl’s Essential Psychopharmacology; The Prescriber’s Guide 4th ed 2011
Tardive Dyskinesia (TD) Up regulation of the postsynaptic dopamine
receptors.
5% of patients maintained on typical antipsychotics will develop TD in 1 year (25% in 5 years).
TD in elderly can be as high 25% in the first year of treatment
Kane JM in Bloom FE, Kupfer DJ, Psychopharmacology: The fourth generation of progress. Philadelphia Raven 1996National Alliance on Mental illness. Tardive dyskinesia Available at www.nami.org/ContentGroups/Helpline1/Tardive_Dyskinesia.html
QuestionWhich of the following risk factors for thedevelopment of TD is most important? Age Gender Mood disorders Substance abuse
QuestionThe estimated annual rate of TD inolanzapine treated patients is: 0.5% 1.0% 2.0% 3% 4%
What happens in the Tuberoinfundibular pathway? With D2 blockade
With 5HT2A blockade
Stahl SM Stahl’s Essential Psychopharmacology; The Prescriber’s Guide 4th ed 2011
Stahl SM Stahl’s Essential Psychopharmacology; The Prescriber’s Guide 4th ed 2011
Cardiometabolic SyndromeWeight gain is mediated by: 5HT2C H1 M3
Stahl SM Stahl’s Essential Psychopharmacology; The Prescriber’s Guide 4th ed 2011
Stahl SM Stahl’s Essential Psychopharmacology; The Prescriber’s Guide 4th ed 2011
Stahl SM Stahl’s Essential Psychopharmacology; The Prescriber’s Guide 4th ed 2011