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DRUG TREATMENT OF PSYCHOSIS

DRUG TREATMENT OF PSYCHOSIS. Psychosis. Psychosis is a thought disorder characterized by disturbances of reality and perception, impaired cognitive functioning, and inappropriate or diminished affect (mood). Psychosis denotes many mental disorders.

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DRUG TREATMENT OF PSYCHOSIS

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  1. DRUG TREATMENT OF PSYCHOSIS

  2. Psychosis Psychosis is a thought disorder characterized by disturbances of reality and perception, impaired cognitive functioning, and inappropriate or diminished affect (mood). Psychosis denotes many mental disorders. Schizophrenia is a particular kind of psychosis characterized mainly by a clear sensorium but a marked thinking disturbance.

  3. Psychosis-Producing Drugs • Levodopa • CNS stimulants • Cocaine • Amphetamines • Khat, cathinone, methcathinone • Apomorphine • Phencyclidine

  4. Schizophrenia • Pathogenesis is unknown. • Onset of schizophrenia is in the late teens - early ‘20s. • Genetic predisposition -- Familial incidence. • Multiple genes are involved. • Afflicts 1% of the population worldwide. • May or may not be present with anatomical changes.

  5. Schizophrenia • Athought disorder. • The disorder is characterized by a divorcement from reality in the mind of the person (psychosis). • It may involve visual and auditory hallucinations, delusions, intense suspicion, feelings of persecution or control by external forces (paranoia), depersonalization, and there is attachment of excessive personal significance to daily events, called “ideas of reference”.

  6. Schizophrenia Positive Symptoms. Hallucinations, delusions, paranoia, ideas of reference. Negative Symptoms. Apathy, social withdrawal, anhedonia, emotional blunting, cognitive deficits, extreme inattentiveness or lack of motivation to interact with the environment. These symptoms are progressive and non-responsive to medication.

  7. Etiology of Schizophrenia Idiopathic Biological Correlates • Genetic Factors • Neurodevelopmental abnormalities. • Environmental stressors.

  8. Etiology of Schizophrenia Characterized by several structural and functional abnormalities in the brains of schizophrenic patients: • Enlarge cerebral ventricles. • Atrophy of cortical layers. • Reduced volume of the basal ganglia.

  9. Dopamine Theory of Schizophrenia Many lines of evidence point to the aberrant increased activity of the dopaminergic system as being critical in the symptomatology of schizophrenia. There is a greater occupancy of D2 receptors by dopamine => greater dopaminergic stimulation

  10. Dopamine Theory of Schizophrenia Dopamine Correlates: • Antipsychotics reduce dopamine synaptic activity. • These drugs produce Parkinson-like symptoms. • Drugs that increase DA in the limbic system cause psychosis. • Drugs that reduce DA in the limbic system (postsynaptic D2 antagonists) reduce psychosis. • Increased DA receptor density (Post-mortem, PET). • Changes in amount of homovanillic acid (HVA), a DA metabolite, in plasma, urine, and CSF.

  11. Pharmacodynamics Anatomic Correlates of Schizophrenia... Areas Associated with Mood and Thought Processes: Frontal cortex Amygdala Hippocampus Nucleus accumbens Limbic Cortex

  12. Dopamine Theory of Schizophrenia Evidence against the Theory? • Antipsychotics are only partially effective in most (70%) and ineffective for some patients. • Phencyclidine, an NMDA receptor antagonist, produces more schizophrenia-like symptoms in non-schizophrenic subjects than DA agonists. • Atypical antipsychotics have low affinity for D2 receptors. • Focus is broader now and research is geared to produce drugs with less extrapyramidal effects.

  13. Dopamine System There are four major pathways for the dopaminergic system in the brain: • The Nigro-Stiatal Pathway. • The Mesolimbic Pathway. • The Mesocortical Pathway. • The Tuberoinfundibular Pathway.

  14. THE DOPAMINERGIC SYSTEM

  15. Catecholamines Tyrosine Tyrosine hydroxylase L-Dopa Dopadecarboxylase Dopamine (DA) Dopamine hydroxylase Norepinephrine (NE) (Noradrenaline)Phenylethanolamine-  -N-methyltransferase Epinephrine (EPI) (Adrenaline)

  16. Tyrosine Dopamine Synapse Tyrosine L-DOPA DA

  17. Dopamine System • DOPAMINE RECEPTORS • There are at least 5 subtypes of receptors: • D1 and D5: mostly involved in postsynaptic inhibition. • D2, D3, and D4: involved in both pre-and postsynaptic inhibition. D2: the predominant subtype in the brain: regulates mood, emotional stability in the limbic system and movement control in the basal ganglia.

  18. Dopamine Reuptake System

  19. Antipsychotic treatments SCHIZOPHRENIA IS FOR LIFE There is no remission

  20. Antipsychotic treatments Schizophrenia has been around perhaps, since the beginning of humankind, however, it was not until the last century that it was established as a separate entity amongst other mental disorders. Many treatments have been devised: • Hydrotherapy: “The pouring of cold water in a stream, from a height of at least four feet onto the forehead, is one of the most certain means of subsiding violent, maniacal excitement that we have ever seen tried”... wrote an anonymous physician in the early 1800’s.

  21. Antipsychotic treatments • Lobotomies (EgazMoniz). • In 1940’s Phenothiazenes were isolated and were used as pre-anesthetic medication, but quickly were adopted by psychiatrists to calm down their mental patients. • In 1955, chlorpromazine was developed as an antihistaminic agent by Rhône-Pauline Laboratories in France. In-patients at Mental Hospitals dropped by 1/3.

  22. Antipsychotics treatment Antipsychotics/Neuroleptics • Antipsychotics are the drugs currently used in the prevention of psychosis. • They have also been termed neuroleptics, because they suppress motor activity and emotionality. ** These drugs are not a cure ** • Schizophrenics must be treated with medications indefinitely, in as much as the disease in lifelong and it is preferable to prevent the psychotic episodes than to treat them.

  23. Antipsychotics/Neuroleptics Although the antipsychotic/neuroleptics are drugs used mainly in the treatment of schizophrenia, they are also used in the treatment of other psychoses associated with depression and manic-depressive illness, and psychosis associated with Alzheimer’s disease. These conditions are life-long and disabling.

  24. Antipsychotics/Neuroleptics NON-compliance is the major reason for relapse.

  25. Antipsychotic/Neuroleptics OLDER DRUGS Three major groups : 1) Phenothiazines 2) Thioxanthines 3) Butyrophenones

  26. Antipsychotics/Neuroleptics • Old antiphsychotics /neuroleptics are D2 dopamine receptor antagonists. Although they are also effective antagonists at ACh, 5-HT, NE receptors. dopamine receptor antagonist D2

  27. Antipsychotics/Neuroleptics • It appears that the specific interaction of antipsychotic drugs with D2 receptors is important to their therapeutic action. • The affinities of most older “classical” agents for the D2 receptors correlate with their clinical potencies as antipsychotics.

  28. Antipsychotic/Neuroleptics Correlations between therapeutic potency and affinity for binding D2 receptors. promazine chlorpromazine clozapine thiothixene [3H]Haloperidol binding IC50 (mol/L) haloperidol spiroperidole Clinical dose of drug [mg d-1]

  29. Antipsychotics/Neuroleptics • Both D1 and D2 receptors are found in high concentrations in the striatum and the nucleus accumbens. • Clozapine has a higher affinity for the D4 receptors than for D2. • Recently it has been found that most antipsychotic drugs may also bind D3 receptors (therefore, they are non-selective).

  30. Antipsychotics/Neuroleptics • Antipsychotics produce catalepsy (reduce motor activity). • BLOCKADE OF DOPAMINE RECPTORS IN BASAL GANGLIA. • Antipsychotics reverse hyperkinetic behaviors (increased locomotion and stereotyped behavior). • BLOCKADE OF DOPAMINE RECPTORS IN LIMBIC AREAS. • Antipsychotics prevent the dopamine inhibition of prolactin release from pituitary. • BLOCKADE OF DOPAMINE RECEPTORS IN PITUITARY. hyperprolactinemia

  31. Pharmacokinetics Absorption and Distribution • Most antipsychotics are readily but incompletely absorbed. • Significant first-pass metabolism. • Bioavailability is 25-65%. • Most are highly lipid soluble. • Most are highly protein bound (92-98%). • High volumes of distribution (>7 L/Kg). • Slow elimination. **Duration of action longer than expected, metabolites are present and relapse occurs, weeks after discontinuation of drug.**

  32. Pharmacokinetics Metabolism • Most antipsychotics are almost completely metabolized. • Most have active metabolites, although not important in therapeutic effect, with one exception. The metabolite of thioridazine, mesoridazine, is more potent than the parent compound and accounts for most of the therapeutic effect.

  33. Pharmacokinetics Excretion • Antipsychotics are almost completely metabolized and thus, very little is eliminated unchanged. • Elimination half-lives are 10-24 hrs.

  34. Antipsychotic/Neuroleptics • Phenothiazines ChlorpromazineThioridazineFluphenazine TrifluopromazinePiperacetazinePerfenazine MesoridazineAcetophenazine Carphenazine Prochlorperazine Trifluoperazine • Aliphatic PiperidinePiperazine* * Most likely to cause extrapyramidal effects.

  35. Antipsychotic/Neuroleptics Piperazine Piperidine Aliphatic Effect [Drug dose]

  36. Antipsychotic/Neuroleptics 2) Thioxanthines Thiothixene Chlorprothixene Closely related to phenothiazines

  37. Antipsychotic/Neuroleptics 3) Butyrophenones Haloperidol Droperidol* *Not marketed in the U.S.

  38. Antipsychotic/Neuroleptics Butyrophenone Phenothiazine Thioxanthene Effect [Drug dose]

  39. Antipsychotics/Neuroleptics • Newer drugs have higher affinities for D1, 5-HT or -AR receptors. • NE, GABA, Glycine and Glutamate have also been implicated in schizophrenia.

  40. Antipsychotics/Neuroleptics The acute effects of antipsychotics do not explain why their therapeutic effects are not evident until 4-8 weeks of treatment. Blockade of D2 receptors  Short term/Compensatory effects: • Firing rate and activity of nigrostriatal and mesolimbic DA neurons. • DA synthesis, DA metabolism, DA release

  41. Antipsychotics/Neuroleptics Presynaptic Effects Blockade of D2 receptors  Compensatory Effects • Firing rate and activity of nigrostriatal and mesolimbic DA neurons. • DA synthesis, DA metabolism, DA release. Postsynaptic Effects Depolarization Blockade Inactivation of nigrostriatal and mesolimbic DA neurons.  Receptor Supersensitivity

  42. Antipsychotic/Neuroleptics Newer Drugs Pimozide Molindone Loxapine Clozapine Olanzapine Qetiapine Risperidone Sertindole Ziprasidone Olindone

  43. Antipsychotic/Neuroleptics ClinicalEx. Py. Drug Potency toxicity Sedation Hypote. Chlorpromaz. Low Medium Medium High Haloperidol High Very High Very High Low Thiothixene High Medium Medium Medium Clozapine Medium Very low Low Medium Ziprasidone Medium Very Low Low Very low Risperidone High Low Low Low Olanzapine High Very Low Medium Very low Sertindole High Very Low Very low Very Low

  44. Antipsychotic/Neuroleptics Chlorpromazine: 1 = 5-HT2= D2 > D1 > M>2 Haloperidol: D2 > D1= D4> 1 > 5-HT2 >H1>M = 2 Clozapine: D4 = 1 > 5-HT2 = M > D2 = D1 = 2;H1 Quetiapine: 5-HT2 = D2 = 1 = 2; H1 Risperidone: 5-HT2 >> 1 > H1 > D2 > 2>> D1 Sertindole: 5-HT2> D2=1

  45. Antipsychotic/Neuroleptics Clinical Problems with antipsychotic drugs include: • Failure to control negative effect • Significant toxicity • Parkinson-like symptoms • TardiveDyskinesia (10-30%) • Autonomic effects • Endocrine effects • Cardiac effects 3) Poor Concentration

  46. DA neuron - ACh neuron Striatum + Substantia Nigra GABA neuron - - GABA neuron - Inhibition of Motor Activity The Nigro-Striatal Pathway

  47. Antipsychotic/Neuroleptics • Some antipsychotics have effects at muscarinicacetylcholine receptors: • dry mouth • blurred vision • urinary retention • constipation Clozapine Chlorpromazine Thioridazine

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