Generalised Anxiety Disorder (GAD) Flashcards

1
Q

Antidepressents

SSRI, Venlafaxine and mirtazapine

A
  1. As an option for treatment of major depression where first-line SSRIs are ineffective or not tolerated
  2. GAD (Venlafaxine)
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2
Q

Venlafaxine and Mirtazepine

MOA

A
  • Venlafaxine is a serotonin and noradrenaline reuptake inhibitor (SNRI), interfering with uptake of these neurotransmitters from the synaptic cleft.
  • Mirtazapine is an antagonist of inhibitory pre-synaptic α2-adrenoceptors. Both drugs increase availability of monoamines for neurotransmission, which appears to be the mechanism whereby they improve mood and physical symptoms in moderate-to-severe (but not mild) depression.
  • Venlafaxine is a weaker antagonist of muscarinic and histamine (H1) receptors than tricyclic antidepressants, whereas mirtazapine is a potent antagonist of histamine (H1) but not muscarinic receptors.
  • They therefore have fewer antimuscarinic side effects than tricyclic antidepressants, although mirtazapine commonly causes sedation.
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3
Q

Venlafaxine and mirtazapine

Adverse effects

A
  • Common adverse effects of both drugs include GI-upset (e.g. dry mouth, nausea, change in weight and diarrhoea)
  • Central nervous system effects (e.g. headache, abnormal dreams, insomnia, confusion and convulsions)
  • Less common but serious adverse effects include hyponatraemia and serotonin syndrome
  • Suicidal thoughts and behaviour may increase
  • Venlafaxine increases QT interval and can increase the risk of ventricular arrhythmias
  • Sudden drug withdrawal can cause GI upset, flu-like symptoms, sleep disturbances
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4
Q

Venlafaxine and mirtazapine

Warnings

A
  • As with many centrally acting medications, the elderly are at particular risk of adverse effects
  • A dose reduction should be considered in people with hepatic or renal impairment
  • Venlafaxine should be used with caution in paitents with CVD associated with an increased risk of arrhythmias
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5
Q

Venlafaxine and mirtazapine

Important interacitons

A
  • The combination of these drugs from other anti-depressant classes can increase the risk of adverse effects (including serotonin syndrome)
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6
Q

Venlafaxine and mirtazapine

Communication

A
  • Advise patients that treatment should improve symptoms over a few weeks, particularly sleep and appetite
  • Discuss referring them for psychological therapy, which may offer greater long-term benefits than drug treatment
  • Explaing that they should carry on with treatment for at least 6 months after they feel better to stop the depression from coming back
  • Warn them not to suddenly stop = withdrawl. Gradual withdrawal must occur over 4 weeks
  • Counsel patients on signs of blood disorders
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7
Q

Gabapentin and pregabalin

A
  1. Both drugs are used for focal epilepsies (with or without secondary generalisation), usually as an add-on treatment when other anti-epileptic drugs e.g. CBZ provide inadequate control
  2. Both are used for neuropathic pain, pregabalin is particularly recommended as a 2nd line option for diabetic neuropathy
  3. Gabapentin is used for migraine prophylaxis
  4. Pregabalin is used for GAD
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8
Q

Pregabalin and gabapentin

MOA

A
  • From a structural point of view, gabapentin is closely related to GABA, the major inhibitory neurotransmitter in the brain
  • However, its MOA although not completely understood, appears largely unrelated to GABA
  • It binds with voltage-sensitive calcium channels (Ca2+), where it presumably prevents inflow of Ca2+ and in doing so, inhibits neurotransmitter release
  • This interferes with synaptic transmission and reduces neuronal excitability
  • Pregabalin is a structural analogue of gabapentin that probably has a similar MOA
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9
Q

Gabapentin and pregabalin

Adverse effects

A
  • Gabapentin and pregabalin are generally better tolerated than other anti-epileptics drugs
  • Their main side effects are drowsiness, dizziness and ataxia, which usually imprvoe over the first few weeks of treatment
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10
Q

Gabapentin and pregabalin

Warnings

A
  • Both drugs depend on the kidneys for their elimination, so their doses should be reduced in renal impairment
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11
Q

Gabapentin and pregabalin

Important interactions

A
  • The sedative effects of gabapentin and pregabalin may be enhanced when combined with other sedating drugs (e.g. BZs)
  • Other than this, gabapentin and pregabalin are notable in having relatively few drug interactions- in stark contrast to most other anti-epileptic drugs
  • This makes them particularly useful where combination regimens are considered necessary
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12
Q

Gabapentin and pregabalin

Communication

A
  • Explain that you are offering a medicine which you anticipate will reduce the severity of their symptoms (e.g. frequency of their fits)
  • Explain that the medicine commonly causes some drowsiness and dizziness
  • For this reason, you will prescribe a low dose initially, the increase this gradually (make surethey are clear on the dosing instructions)
  • Explain that these side effects should improve over the first few weeks
  • They should avoid driving or operating machines until they are confident that the symptoms have settled
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13
Q

Gabapentin and pregabalin

Monitoring

A
  • The best guide to clinical effectiveness is to enquire about symptoms (e.g. seizure frequency) and side effect
  • There is no need to monitor serum/plasma concentrations of gabapentin or pregabalin
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