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Y4 Psychiatry > 9 - Psychiatric Drug Reactions > Flashcards

9 - Psychiatric Drug Reactions Flashcards

1
Q

If a patient asks you if antidepressants are addictive what should your response be?

A

No

Only criteria of addiction it fits is ‘withdrawal’ symptoms which is discontinuation syndrome.

e.g no increased tolerance, no cravings

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2
Q

What is discontinuation syndrome?

A
  • Onset is within 5 days of stopping, sometimes after cross-tapering or missing doses
  • Usually mild and self-limiting but can be prolonged and severe
  • Warn patients about this and explain it is normal
  • SSRIs: ’Flu-like symptoms, headaches, dizziness, insomnia, tears, irritability, vivid dreams
  • MAOIS: Agitation, irritability, ataxia, movement disorders, insomnia
  • TCAS: ’Flu symptoms; insomnia
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3
Q

Which antidepressants are associated with the worst discontinuation syndrome?

A
  • Paroxetine
  • Venlaxafine
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4
Q

How can the effects of discontinuation syndrome be avoided?

A
  • Slow taper down dose
  • Snap tablets in half or take on alternate days
  • Switch to Fluoxetine (long half-life) and taper down from that
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5
Q

How does the half-life of an antidepressant determine the likelihood of serotonin syndrome and discontinuation syndrome?

A

Long Half-Life: More likely to have serotonin syndrome

Short half life: More likely to have discontinuation syndrome

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6
Q

What is Serotonin Syndrome and how does it present?

A

Life-threatening neurological disorder due to increased serotonergic activity in the CNS

Triad of:

-Mental status changes

-Autonomic hyperactivity e.g HTN, Hyperthermia, Tachycardia

-Neuromuscular abnormalities e.g rigidity, clonus, hyperreflexia

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7
Q

Which antidepressants are most associated with serotonin syndrome?

A

SSRIs

Can be due to a single drug or a combination that increase serotonergic activity

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8
Q

What are some signs and symptoms of serotonin syndrome?

A

DILATED PUPILS

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9
Q

What is the criteria for a diagnosis of serotonin syndrome?

A

Hunter Criteria

Patient taking serotonergic agent presents with one of:

  • Spontaneous clonus
  • Inducible/ocular clonus and agitation or diaphoresis
  • Tremor and hyperreflexia
  • Hyperthermia, hypertonia, and ocular/inducible clonus
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10
Q

What are some differential diagnoses for serotonin syndrome?

A
  • Neuroleptic malignant syndrome
  • Malignant Hyperthermia
  • Encephalitis
  • Drug intoxication (MDMA and Cocaine)
  • Phaeochromocytoma
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11
Q

What investigations should you do if you suspect serotonin syndrome?

A
  • Bedside: ECG, cardiac monitoring (particularly if profound autonomic symptoms), blood glucose, urine dip
  • Bloods: CK, FBC, U+ES, LFTs, and blood gas. Patients may have features of neutrophilia, acute kidney injury, or elevated CK levels
  • Imaging: cerebral imaging (i.e. CT/MRI) may be needed in patients with new-onset altered mental status to exclude an alternative cause
  • Special: a lumbar puncture may be needed to exclude an intracerebral infection or investigate for an alternative cause of confusion (e.g. autoimmune encephalopathy).
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12
Q

How is serotonin syndrome managed?

A
  • Stop serotonergic agent
  • Monitor for 4-6 hours. Resolves in 24 hours
  • Supportive: fluids for AKI, cooling blankets, benzos for agitation,
  • Medical: if supportive and benzos fail give Serotonin antagonist Cyproheptadine
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13
Q

When is the QT period prolonged?

A
  • 450ms in men
  • 470ms in women
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14
Q

What are some complications of serotonin syndrome?

A
  • Cardiac arrest
  • Cardiac arrhythmias
  • AKI
  • Rhabdomyolysis
  • DIC
  • Seizures
  • Respiratory failure
  • VTE
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15
Q

When is the QT interval prolonged?

A
  • 450 ms for men
  • 470ms for women
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16
Q

What is Neuroleptic Malignant Syndrome?

A

Life-threatening neurological disorder characterised by confusion, fever, muscle rigidity and autonomic instability

Affects up to 3% of patients on antipsychotics (neuroleptics), more men

17
Q

What drug causes NMS the most?

A

FGA

  • Haloperidol
  • Fluphenazine
18
Q

How long after taking an antipsychotic can NMS occur?

A

Within first 2 weeks

Usually recovers within 2 weeks of stopping agent

19
Q

What are some risk factors for developing NMS?

A
  • Higher antipsychotic doses
  • High-potency antipsychotics
  • Concomitant drug use (e.g. lithium)
  • Depot formulations (i.e. long-acting)
  • Acute medical illness (e.g. trauma, infection)
  • Acute catatonia (state or immobility)
  • Previous NMS
  • Male
20
Q

What are the clinical features of NMS?

A
  • Altered mental status: agitation and delirium
  • Rigidity: felt as a generalised increase in tone
  • Fever (>38º)
  • Dysautonomia: tachycardia, labile blood pressure, profuse sweating and/or arrhythmias.
  • Pupils normal or constricted
21
Q

What blood test should you do for NMS?

A

Elevated CK due to muscle rigidity (e.g. >1000-100,000 IU/L)

May be normal if rigidity not profound or if early in the presentation

22
Q

How is NMS managed?

A

Supportive:

  • Stop antipsychotic
  • Cardiac monitoring
  • Give benzodiazepines for agitation
  • Fluid resus
  • Cooling blankets

Specific

  • Dantrolene or Lorazepam or Bromocriptine to relax muscles
  • Fluids and Sodium Bicarbonate for rhabdomyolysis
  • Clonidine for profound HTN
23
Q

What are the complications with NMS?

A
  • Cardiac arrest
  • Cardiac arrhythmias
  • Acute kidney injury
  • Rhabdomyolysis
  • Disseminated intravascular coagulation
  • Seizures
  • Respiratory failure
  • Venous thromboembolism
24
Q

How can you tell the difference between NMS and SS?

A
25
Q

What is an acute dystonia?

A

Sustained often painful muscle spasms producing abnormal postures common with antipsychotics

Occur in first 48 hours to 5 days of taking antipsychotic

Most common: neck, tongue, jaw, oculogyric crisis

26
Q

How are acute dystonia treated?

A
  • Stop antipsychotic
  • IM or IV Procyclidine (Anticholinergic)
  • Long term prophylactic when back on antipsychotic
27
Q

How is Clozapine agranulocytosis managed?

A
  • Stop Clozapine
  • Stop other bone marrow suppressing drugs e.g Valproate
  • Avoid antipsychotics for a few weeks
  • Contact haematologist
  • Avoid infection (e.g isolate) and consider prophylactic broad spectrum antibiotics
  • Give lithium or G-CSF to raise WCC and neutrophils

Y4 Psychiatry (17 decks)

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