Generalised Anxiety Disorder (GAD) Flashcards
1
Q
Antidepressents
SSRI, Venlafaxine and mirtazapine
A
- As an option for treatment of major depression where first-line SSRIs are ineffective or not tolerated
- GAD (Venlafaxine)
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.
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
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
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)
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
7
Q
Gabapentin and pregabalin
A
- 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
- Both are used for neuropathic pain, pregabalin is particularly recommended as a 2nd line option for diabetic neuropathy
- Gabapentin is used for migraine prophylaxis
- Pregabalin is used for GAD
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
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
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
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
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
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