Drugs acting on the CNSI

Unit 8

Week 5

Dr.Mohammed Hassan

Al-Hamadi , Drugs acting on the CNSI. 4medstudents.com 2003

Drugs acting on the CNS 1 The psychotic disorders are classified into 3

major groups: Anxiety disorders (phobia and sleeping

disorders). Effective/mood disorders (depression) Personality disorders (Schizophrenia)

Anxiolytic Drugs: Benzodiazepines(BDZ) Barbiturate. Buspirone

Antidepressant Drugs: Tricyclic/Plycyclic Monoamine oxidase inhibitors Selective serotonin-reuptake inhibitors (SSRI)

Neurolytic Drugs: Phenothiazin Buteopheanol

Drugs acting on the CNS 1

Anxiety and Anxiolytic Drugs: Anxiety:

Definition: Unpleasant state of tension or a fear that seems to

arise from an unknown source. Symptoms:

Tachycardia Sweating Palpitations Sympathetic activation

Diazepam,Lurazepam, Midazolam Mode of action:

Binding of GABA to its receptor trigger an opening of chloride conductance. The influx of chloride ions causes hyperpolarization that moves the post synaptic potential away from its firing threshold and thus inhibits the formation of action potential and neural firing>

Actions: Reduction of anxiety( at low doses) Sedative and hypotonic actions (at higher doses) Anticonvulsant Muscle relaxant

Anxiolytic Drugs(Benzodiazapine)

Benzodiazapine Therapeutic uses:

Anxiety disorders (Muscular disorders Seizures Sleep disorders

Pharmacokinetics: Absorption and distribution:

Lipophilic Rapidly absorbed

Benzodiazapine Pharmacokinetics:

Duration of action: Short, intermediate and long acting.

Fate: Metabolized by the hepatic microsomal metabolism

system.

Dependence: At high doses Results in withdrawal symptoms:

Confusion, anxiety, restlessness and tension.

Benzodiazapine Adverse effects:

Drowsiness and confusion. Precautions:

Cautiously in treating patients with liver disease.

Phenobarbiturate, amobarbiturate Mode of action:

Interfere with sodium and potassium transport across cell membranes.

Actions: Depression of CNS (at low doses) Hypnosis and anesthesia ( at high doses) Respiratory depression. Enzyme induction (P-450 microsomal enzyme in

liver)

Welcome (Barbiturate)

Barbiturate Therapeutic uses:

Anesthesia Anticonvulsant Anxiety

Pharmacokinetics: Metabolized by the liver Distributed to:

Splanchnic area Skeletal muscles Adipose tissue

Barbiturate Adverse effects:

CNS: Drowsiness, impaired concentration and mental

sluggishness Drug hangover

Tiredness, nausea and dizziness Addiction:

Tremor, anxiety, tiredness, restlessness, nausea and vomiting

Poisoning: death

WelcomeBuspirone

Useful in the treatment of generalized anxiety disorders.

Action: The action is mediated by serotonin receptors.

Adverse effects: Dizziness Nervousness ligthheadness The action is mediated by serotonin receptors

Depression and Antidepressant drugs: depression:

Definition: Pervasive mood altering illness affecting energy, sleep,

appetite and the ability to function. Symptoms:

Depression Sadness Hopelessness Inability to experience pleasure in usual activity

Amitriptyline, Imipramine Mode of action:

Inhibit the neuronal reuptake of norepinephrine and serotonin into presynaptic nerve terminals which leads to increased concentration of monoamine in the synaptic clef.

Blocking serotonergic,a-adrenergic, histamine and muscurinic receptors.

Actions: Elevate moods Improve mental alertness Increase physical activity

Antidepressant Drugs(Tricyclic/Polycyclic)

Tricyclic/Polycyclic Therapeutic uses:

Depression Panic disorder Bed-wetting in children

Pharmacokinetics: Absorption and distribution:

Lipophilic Low bioavailability Metabolized by hepatic microsomal system

Tricyclic/Polycyclic antidepressant Adverse effects:

Anti muscarinic effects: Blurred vision, dry mouth, urinary retention and

constipation Increase cardiovascular stimulation Sedation Orthostatic hypotension:

By blocking a-adrenergic receptors.

Hydralazine, phenelzine Mode of action:

Reverrsibly or irreversibly inactivate the enzyme, this result in increased norepinephrine, serotonin and dopamine with in the neuron.

Welcome (monoamine oxidase

inhibitors)

monoamine oxidase inhibitors Therapeutic uses:

Depression Phobic states

Pharmacokinetics: Effect require 2 to 4 weeks

monoamine oxidase inhibitors Adverse effects:

Inability to degraded tyramine obtained from the gut Cheese Chicken liver

Tyramine causes the release of large amounts of stored catecholamines from verve terminals resulting in:

Headache Tachycardia Nausea hypertension

Fluoxetine Actions:

Inhibit serotonin reuptake ( selective for serotonin) Therapeutic uses:

Depression Panic disorders Pre menstrual syndrome

Welcome (Selective Serotonin-Reuptake

Inhibitors)

Selective Serotonin-Reuptake Inhibitors

Pharmacokinetics: Slowly cleared from the body Potent inhibitor of a hepatic cytochrome P-450.

Adverse effects: Nausea Anxiety Insomnia Sexual dysfunction Weight loss tremors

Personality disorders and antipsycotic (neuroleptic) Drugs:

schizophrenia Definition:

Mental disorder caused by some inherited dysfunction of the brain.

Symptoms: Delusions Hallucination Thinking or speech disturbance

Five important classes. Most important classes are:

Phenothiazines Fluphenazine Promethazine

Butyrophenones Haloperidol Doroperidol

Mode of action: Block dopamine and serotonin receptor in the brain Many of these drugs also block cholinergic, adrenergic

and histamine receptors

(neuroleptic drugs)

neuroleptic drugs Actions:

Antipsychotic actions: Reduce hallucinations by blocking dopamine receptors.

Extrapyramidal effects: Parkinson syndrome by blocking the dopamine

receptors in the nigrostriatal pathway. Antiemetic effects:

By blocking dopaminergic receptors. Antimuscarinic effects:

Blurred vision, dry mouth, sedation and confusion. Other effects:

Hypotension and lightheadedness by blocking a-adrenergic receptors

neuroleptic drugs Therapeutic uses:

Schizophrenia Prevention of severe nausea Treatment of severe pain

Adverse effects: Tremors Postural hypotension Constipation Urinary retention Confusion Sexual dysfunction

Thank You Team