Psychiatry Pharmacology Flashcards
What is the monoamine hypothesis?
depletion of monoamine neurotransmitters; noradrenaline, serotonin and dopamine – or a change in their receptors’ function.
What is support for monoamine theory?
antidepressants increase the levels of monoamine neurotransmitters, amphetamines/cocaine increase the levels of monoamines in synaptic cleft and can elevate mood, reserpine decreases levels of monoamines pre-synaptically and can depress mood and CSF levels of 5-HIAA (serotonin metabolite) are decreased in depression sufferers.
What is dopamine hypothesis?
increased levels of dopamine in the brain –> schizophrenia
What is support for the dopamine hypothesis?
amphetamines increase dopamine release and in high doses can induce a psychosis, amphetamines and other dopaminergic agents exacerbate the symptoms of schizophrenia, dopamine antagonists are effective in treatment of schizophrenia and clinical potency of 1st gen antipsychotics is correlated to their affinity for D2 receptors.
Elements of the revised dopamine hypothesis?
Positive symptoms = hyperdopaminergia in mesolimbic system
Negative symptoms = hypodopaminergia in mesocortical system
Nigrostriatal tract = responsible for EPSE of AP medication
Tuberoinfundibular tract = responsible for endocrine side-effects of AP medication
Neurotransmitter theory in dementia?
- Acetylcholinesterase inhibitors increase cholinergic transmission – in AD there is a depletion of Ach and neurones that use Ach – can modestly and temporarily ameliorate cognitive performance and behavioural problems in a minority of patients with mild to moderate AD and LB dementia.
- NMDA receptor antagonists protect neurones from glutamate-mediated neurotoxicity – NMDA receptors allow increased release of Ca2+ into cells oxidative stress and cell death – effective in moderate to severe AD.
Examples of SSRIs?
Fluoxetine, Citalopram, Sertraline, Escitalopram, Fluvoxamine, Paroxetine
Mechanism of action of SSRIs?
Selectively inhibit the reuptake of serotonin (5-HT) at synaptic cleft. Not toxic in overdose.
Clinical indications of different SSRIs?
Citalopram - depressive illness, panic disorder
Sertraline – depressive illness, OCD, panic disorder, PTSD, social anxiety disorder
Fluoxetine – major depression, bulimia nervosa, OCD
Escitalopram – depressive illness, GAD, OCD, panic disorder, social anxiety disorder
Fluvoxamine – depressive illness, OCD
Paroxetine – major depression, OCD, panic disorder, social anxiety disorder, PTSD, GAD
Side effects of SSRIs?
Mild GI, loss of libido, dizziness, dry mouth, blurred vision, sweating, headaches, hyponatraemia.
Suicide risk – risk of suicide can be increased in early stage of treatment due to increased motivation.
Serotonin syndrome.
Examples of tricyclic antidepressants?
Dibenzocyclophenates = Amitriptyline, Nortriptyline
Iminodibenzyls = Clomipramine, Imipramine, Trimipramine,
Others = Dosulepin, Doxepin, Lofepramine
Mechanism of action of TCAs?
Inhibit reuptake of noradrenaline and serotonin and also have antagonist activities at a variety of neurotransmitter receptors.
Clinical indications of TCAs?
Clinical depression – more effective than SSRIs for severe depression, but should be used cautiously in the elderly and physically ill. Should be avoided in suicidal patients due to toxicity in overdose.
Side effects of TCAs?
Antimuscarinic = dry mouth, blurred vision, constipation, urinary retention, sedation, nausea Antiadrenergic = postural hypotension, sedation Antihistaminergic = sedation, weight gain Cardiotoxic = Arrhythmias (↑ventricular conduction time - contraindicated in patients with recent MI and in those with heart block) Neurotoxic = delirium, movement disorders, convulsions
Interactions of TCAs?
Dental anaesthetics containing lignocaine, MAOIs
Example of a NARI?
Reboxetine
Mechanism of NARIs?
Selectively inhibit reuptake of noradrenaline in the brain.
Clinical indications of NARIs?
Indicated in severe depression, usually second or third line. More effective than SSRIs in severe depression. Less likely than SSRIs to trigger mania in BAD or convulsions in epilepsy. Very low toxicity and wide safety margin – safe in overdose.
Examples of SNRI? (Serotonin and Noradrenaline RI)
Duloxetine, Venlafaxine
Mechanism of action of SNRIs?
Selectively inhibit the reuptake of noradrenaline and serotonin in the brain.
Indications of SNRIs?
Indicated in treatment-resistant depression – may have better efficacy and more rapid onset of action than SSRIs in some cases.
Also indicated in GAD.
Side effects of SNRIs?
Similar side effect profile to SSRIs – may cause hypertension and heart disease so shouldn’t be used in patients with heart disease, uncontrolled hypertension or electrolyte imbalance.
Monitoring of SNRIs?
ECG and blood pressure measurement should be undertaken prior to starting treatment and BP measurements should be undertaken at regular intervals thereafter.
Example of NaSSa? (Noradrenaline and serotonin -speicifc antidepressant)
Mirtazapine
Mechanism of action of NaSSa?
Enhances noradrenergic and serotonergic neurotransmission. Antagonist at 5-HT2 and 5-HT3 receptors and central α2-adrenoreceptors. Increases central noradrenaline release by antagonising inhibitory α2-adrenoreceptors. Also increases serotonin release by both enhancing a facilitatory noradrenergic input to serotonergic cell bodies and antagonising inhibitory pre-synaptic α2-adrenoreceptors on serotonergic neuronal terminals.
Clinical indications of NaSSa?
Used as second or third line treatment for depression (severe)
Side-effects of NaSSa?
Weight gain, sedation, dry mouth. Becomes less sedative as dose is increased.
Less sexual side effects than other antidepressants. Safe in overdose.
Examples of MAOIs?
Phenelizine, Isocarboxazid, Tranylcypromine
Mechanism of MAOIs?
Inhibit metabolic degradation of monoamines by monoamine oxidase.
Interactions of MAOIs?
- Interact with tyramine-containing foods (cheese, red wine) –> inhibition of peripheral metabolism of tyramine –> hypertensive crisis. Also avoid indirectly acting sympathomimetic amines (amphetamine, ephedrine, fenfluramine, phenylpropanolamine) – present in many cough mixtures and nasal decongestants.
- Avoid L-Dopa, pethidine, insulin and barbituates.
- Can interact dangerously with tricyclics
- TCA/SSRI should not be started until 2 weeks after stopping a MAOI. A MAOI should not be started until at least 7-14 days after stopping a TCA/SSRI.
Monitoring/overdose in MAOIs?
Overdose = extremely serious and should lead to immediate hospitalisation. Signs/symptoms may be absent in initial 12-hour period following overdose.
Example/mechanism of RIMA? (reversible inhibitor of monoamine oxidase A)
Moclobemide – selective for MAO-A, not B. Is also reversible so can be displaced by tyramine, therefore much less likely to cause a food or drug interaction.
Examples of first generations antipsychotics?
Butyrophenones = Haloperidol
Thioxanthenes = Flupentixol, Zuclopenthixol
Diphenylbuytlpiperidines = Pimozide
Aliphatic (Phenothiazines) = Chlorpromazine, Levomepromazine
Piperazines (Phenothiazines) = Fluphenazine, Trifluoperazine
Piperidines (Phenothiazines) = Pipotiazine palmiate
Mechanism of action of first generation antipsychotics?
Block postsynaptic dopamine D2 receptors in the CNS. Antidopaminergic action on the mesolimbic system is the effect required – dopamine hypothesis. Antidopaminergic action on other systems (tuberoinfundibular and nigrostriatal pathways) results in adverse side effects.
Clinical indications of 1st gen antipsychotics
Indicated in the treatment of schizophrenia, the acute symptoms of mania and psychotic symptoms resulting from organic disorders and psychoactive substance abuse.
Classes of side-effects of 1st gen antipsychotics?
Tuberoinfundibular (dopamingergic) Nigrostriatal (dopaminergic) Acetylcholine (muscarinic) Adrenaline/noradrenaline Histamine Neuroleptic malignant syndrome
Tuberoinfundibular (dopaminergic) side effects of 1st gen antipsychotics?
Dopamine is prolactin inhibitory factors, so typical antipsychotics cause hyperprolactinaemia –> galactorrhoea, gynaecomastia, menstrual disturbances, reduced sperm count and reduce libido.
Nigrostriatal (dopaminergic) side effects of 1st gen antipsychotics?
Antidopaminergic action on NS system results in extrapyramidal side-effects (EPSE).
Parkinsonism, Acute Dystonias, Akathisia, Tardive Dyskinesia.
Antimuscarinic side-effects of 1st gen antipsychotics?
Dry mouth, blurred vision, urinary retention, nasal congestion, constipation. Central antimuscarinic actions can lead to convulsions and pyrexia.
Adrenaline/noradrenaline side effects of 1st gen antipsychotics?
Postural hypotension, failure of ejaculation
Histamine side effects of 1st gen antipsychotics?
edation (can be a benefit), weight gain
What is neuroleptic malignant syndrome?
Potentially fatal toxic delirious state. Characterised by: autonomic dysfunction (hyperthermia, tachycardia, labile blood pressure, pallor, sweating); fluctuating level of consciousness; muscular rigidity; urinary incontinence.
Requires urgent medical treatment. Lab results show ↑serum CK and ↑WBC count.
What can you do for people on 1st gen antipsychotics who are bad at taking their medications?
Typical AP medication can be given by depot injection – administered by deep IM injection at intervals of 2-8 weeks. Benefit is improved compliance, less potential for abuse/overdose and improved bioavailability.
Only one atypical AP medication available for depot – risperidone.