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Head and Neck Pharmacology > Antipsychotics > Flashcards

Antipsychotics Flashcards

1
Q

Antipsychotics are also known as?

A

neuroleptics
antischizophrenics drugs
major tranquilisers.

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2
Q

Antipsychotics are highly effective in what states?

A

in excited or agitated psychotic states, including acute episodes of:
1. Schizophrenia
2. Hypomania
3. Delirium

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3
Q

What do antipsychotics do?

A
  • generally lower the seizure
    threshold and induce extrapyrimidal effects.
  • They exert profound effect on the ANS, hypothalamus, reticular formation and the medulla.
    Note: They do not exhibit an addictive potential or anaesthetic properties
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4
Q

Most antipsychotics are?

A

Dopamine Antagonists (D1 and / or D2)
- have side effects

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5
Q

Most antipsychotics block?

A

5-HT, Histamine, Muscarinic (Ach) and alpha-1 receptors
- have side effects and adverse reactions

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6
Q

Side effects due to Blockade of D2 receptor?

A
  1. Parkinsonism like symptoms (Extrapyramidal Effects)
  2. Tremor /Rigidity
  3. Dystonia (grimacing, spastic limbs, eye rolling upwards)
  4. Akathisia (Restless, fidgeting, pacing)
  5. Tardive Dyskinesia (face, tongue, jaw movements)
  6. Also amenorrhoea ♀, loss of libido ♂
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7
Q

Side effects due to Blockade of alpha-1 Receptors?

A

postural hypotension

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8
Q

Side effects due to Blockade of Muscarinic (M) Receptors?

A

Dry mouth, blurred vision, constipation, urinary retention

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9
Q

Side effects due to blockade of Histamine (H) Receptors?

A

Drowsiness, sedation

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10
Q

Dosage of antipsychotics?

A
  • Low doses used initially
  • Takes 2-3 weeks for drug to work
  • The effects on the psychotic ‘episode’ may take 3 weeks
    > Difficult to determine correct dose for an individual
    -Patient compliance a big problem (mainly from side effects)
    > Depot injections or Syrups available
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11
Q

Anti-Psychotic Drug Groups
(Classification)?

A
  1. Typical Anti-Psychotic
  2. Atypical Anti-Psychotic
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12
Q

Typical antipyschotics?

A

First generation (Typical) antipsychotics - Newer class of Anti-Psychotics

  1. Action
    they produce a blockade of Dopamine D2 receptors AND Selective 5-HT2 antagonism
    Examples
    Chlorpromazine, haloperidol, fluphenazine, flupentixol, Clopentixol
  2. Side effects
    Minimal extrapyrimidal side effects BUT In some patients causes death through ‘agranulocytosis’ (lack of white blood cells) Monitor WBC count – very important (Clozapine)
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13
Q

Atypical antipyschotics?

A

Second generation (Atypical) antipsychotics - Large class of anti-psychotics

Side effects
Vary in their side effects
e.g.
1. Chlorpromazine: Low potency
- Adverse Side effects (Sedation & Parkinsonism.)
2. Flupenthixol : Used in depot injections
- Rapid onset
- Long Acting.
- Also anti-depressant properties.
- Adverse side effects (Sedation, Parkinsonism. )

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14
Q

Distinction between the two groups rests on?

A
  1. Receptor profile
  2. Incidence of extrapyrimidal side effects
  3. Efficacy in treatment resistant patients
  4. Efficacy against negative symptoms
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15
Q

Acrions of chlorpromazine?

A
  1. It blocks noradrenaline, dopamine, serotonin, Ach and histamine receptor sites
  2. It has an effect on the endocrine glands
  3. It is a standard against which other drugs are compared
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16
Q

Pharmacological actions of chlorpromazine?

A
  1. Drowsiness and tendency to fall asleep, but arousal can be achieved with little stimulation.
    - Large doses does not induce anaesthesia.
  2. Potentiates depressant action of sedative-hypnotics & anaesthetics.
  3. Antagonizes the stimulant effects of amphetamine & related drugs that produce steriotyped behaviour.
  4. Potentiates actions of analgesics
  5. Produces tiredness, sedation & diminution of emotional responsiveness, with indifference to environmental changes. (Ataractic state)
  6. Inhibits the CTZ thus has antiemetic properties
17
Q

CPZ vs hypothalamus?

A

Inhibits hypothalamic function, thus causes
1. temperature control (hypothermia)
2. increased prolactin release leading to galactorrhea, amenorrhea, delayed menstruation and weight gain

18
Q

CPZ vs receptors?

A
  1. Powerful extrapyramidal effects
  2. Blocks muscurinic cholinergic 3. receptors, and produces atropine like effects.
  3. Blocks histamine H1 receptors
  4. Blocks alpha-adrenoreceptors, which plays a part in the production of postural hypotension., which is also due to central impairement of CVS reflexes.
19
Q

Site and mode of action of CPZ?

A
  • CPZ and other phenothiazines exert a relatively selective action on those parts of the CNS that are concerned with alertness and performance.
  • Selectivity is due, in part, to the preferential accumulation in the reticular activating system, limbic system, hypothalamus and thalamus.
  • Very small amounts are found in the cerebral and cerebella cortices
20
Q

How CPZ decreases alertness?

A

The decreased alertness is possibly due to the blockade of input into the reticular formation from collaterals of second - order sensory nerves ascending to the cerebral cortex.
In addition, there is inhibition of activity in thalamic nuclei through which impulses from the reticular formation pass to the cortex producing arousal

21
Q

CPZ has antagonistic activity in the following order of potency?

A
  1. Against alpha-receptor agonists
  2. Dopamine
  3. Histamine
  4. Muscurinic agonists
  5. Bradykinin
    Note: It is not clear as to what extent the central effects of CPZ are attributable to any one or a combination of these actions.
22
Q

Name and describe the various effects and their causes that CPZ causes?

A
  1. Tranquilizing action of CPZ is due to blockade of central adrenergic transmission.
  2. Antischizophrenic activity is due to blockade of serotoninergic dopaminergic transmission
  3. Antiemetic effect and extrapyramidal effects are due to blockade of dopaminergic transmission.
23
Q

Antipsychotic drugs produce two
pharmacological actions?

A
  1. Their ability to improve schizophrenia condition
  2. Their ability to evoke extrapyrimidal syndromes
24
Q

Pharmacokinetics of CPZ?

A
  1. Orally well absorbed with a 30% bioavailability. (decreased by the presence of food, anticholinergics or antacids)
  2. Peak plasma levels reached in 2-3 hours.
  3. Half time varies 2 to 24 hours in different people.
  4. Plasma steady state is reached in 1 week.
  5. A single night time dose is advisable.
  6. CPZ undergoes hepatic metabolism & has 168 metabolites by:
  7. Demethylation producing active nor1 & nor2 chlorpromazine which are sedative.
  8. Oxidation producing inactive sulphoxides and N-oxides.
  9. Hydroxylation producing 3-hydroxy and 7-hydroxychlorpromazine and the latter is implicated in skin pigmentation and has more antipsychotic properties than the parent compound.
  10. Toxicity is observed at concentrations above 600mg/ml.
  11. The rate of excretion is slow.
25
Q

Therapeutic uses of CPZ?

A
  1. Schizophrenia, Mania, Anxiety neurosis, Huntingtons disease
  2. Drug induced psychosis
  3. Shock, Nausea , Vomiting and Hiccup
  4. Withdrawal symptoms
  5. Pruritis (itchy skin)
  6. Mental retardation
  7. Painful terminal illnesses (to reduce emotional response to pain)
26
Q

Adverse effects of CPZ?

A
  • All antipsychotic drugs produce adverse reactions that are extensions of their pharmacological effects.
  • They are remarkably safe with a wide margin of safety, and overdoses are rarely fatal in adults.
  • The dose response curve is flat and can be used over a wide dose range
27
Q

Disturbances of the CNS by phenothiazines?

A

Drowsiness, lethargy & fatigue are common especially in initial therapy

28
Q

Extrapyrimidal effects of phenothiazines?

A
  1. Parkinsonism (tremor & rigidity)
  2. Akathesia (aimless motor restlessness)
  3. Dystonia (tonic contractions of groups of muscle)
  4. Tardive dyskinesia (serious but rare toxicity –faciobucculolinguo-musticatory dyskinesia. Uncontrolled rhythmic, in-&-out movements of the tongue. Spasms of the glottis and respiratory muscle may endanger life
  5. Convulsant action They may precipitate epileptyform seizure in susceptible individuals
  6. Endocrine effects. These are due to disruption of hypothalamic control over the pituitary, causing suppression of prolactin-inhibitory factor from the hypothalamus, leading to increased blood prolactin levels. (breast enlargement in men – gynaecomastia, & lactation - galactorrhoea in women.
  7. False pregnancy tests have also been reported.
29
Q

Disturbances of the ANS function by phenothiazines?

A
  1. Postural hypotension tachycardia (dose related is common during early stages of treatment.
  2. Anticholinergic effects Dry mouth, constipation, urinary retention and blurred vision. Tolerence to these side effects may develop and atropine like effects may worsen glaucoma.
  3. Nasal congestion. May occur during alpha-adrenoreceptor blockade.
  4. Sexual function Failure to ejaculate. Libido is decrease in men and increased in women.
  5. Temperature control. Temp control of the thalamus goes out of function
30
Q

Non phenothiazine antipsychotics?

A
  1. Butyrophenones – Haloperidol is an effective alternative to phenothiazines. Less sedative to CPZ, but more potent antiemetic and more prone to produce extrapyrimidal effects.
  2. Thioxanthines - Chlorprothixane, an analogue of CPZ. Its side effects and pharmacological effects are similar to phenothiazines.
  3. Dihydroindolone – Malindone has a long duration of action and its effects are similar to phenothiazines. Extrapyrimidal incidents are lower.
  4. Dibenzodiazepines. – Clozapine, a unique antipsychotic because of low incidence of extrapyrimidal. It resembles CPZ
31
Q

Depot Neuroleptics?

A
  • Fatty acid esters of phenothiazines are increasingly being used for the maintenance therapy in schizophrenics.
  • Single injections may be effective for 2-4 weeks.
  • The ester link is broken by tissue esterases to release the free drug, which is then absorbed from the site of injection.

Head and Neck Pharmacology (5 decks)

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