Psych - Antidepressants Flashcards
Name some SSRIs and dosages
- Sertraline (50-200mgs) - safest in cardiac disease (100mg = therapeutic dose)
- Citalopram (20-40mgs)/Escitalopram (10-20mgs) watch out for QTc, especially if are on other medication that can prolong QTc
- Fluoxetine (20-60mg) - has longest T1/2 t/f have to watch out for serotonin syndrome when switching
- Paroxetine (20-60mg) - watch out for discontinuation syndrome (has shorter T1/2)
How do SSRIs work? Name side effects
- MoA: increase serotonin activity by reducing the presynaptic reputable of serotonin after release. Causes more serotonin to sit in nerve junction and leads to a down regulation of post-synaptic receptors
- SEs:
- weight changes and sexual dysfunction (biggest barriers to patient compliance)
- sense of restlessness/agitation/initiation, nausea, GI disturbance.
- Hyponatraemia: esp in elderly due to SIADH
- Less common:
- Bleeding (can cover with PPI, serotonin is found on platelets, avoid in previous stomach ulcer, and in patients over 80 years old)
- Suicidal ideation (needs careful monitoring, esp in younger population)
How do SSRIs affect QT interval? What are CIs of these drugs?
- Citalopram and escitalopram are associated with dose-detensint QT interval prolongation
- Should not be used in those with congenital long QT syndrome, known pre-existing QT interval prolongation or with any otehr medcations that prolong QT
- Pts with hepatic impairment should be on lower doses of these drugs
Name some important SSRI-drug interactions
- NSAIDs: only co-prescribe an SSRI if give PPI cover
- Warfarin/heparin: avoid SSRI and consider Mirtazapine
- Triptans and MAOIs: increased risk of serotonin syndrome
Should SSRIs be prescribed in pregnancy? What are important SEs in pregnancy?
- Must weigh up the benefits and risk when deciding whether to use in pregnancy or not
- Use during 1st trimester: small increased risk of congenital heart defects
- Use during 3rd trimester: can result in persistent pulmonary hypertension
- Paroxetine: increased risk of congenital malformations, esp in 1st trimester.
Explain the MoA of SNRIs and list some SEs
- Act in same way as SSRIs but bind to noradrenaline reuptake receptors as well
- Small evidence base for neuropathic pain
- SEs: same as SSRIs + greater potential for sedation, nausea and sexual dysfunction
Name 2 SNRIs and dosages
- Duloxetine (60-120mg)
- Venlafaxine (75-375mg): greater efficacy and go to a higher dose but caution with higher doses in heart disease b/c can be cardiotoxic - must monitor BP
What is Mirtazapine? What are the major side effects?
-Noradrenergic and specific serotonergic antidepressants -Stand alone drug - strong H1 (histamine) activity - hence sedation and increased appetite -SEs: sedation and weight gain (even at low doses) - these can be used to therapeutic advantage
What are TCAs? List some SEs
-Out of favour now but are reasonable alternative for pts who do not respond to SSRIs -Newer TCAS (lofepramine and nortriptyline) are better tolerated than older ones (Amitriptyline) -SEs: muscarinic and histaminic - anticholinrgic syndrome, drowsiness *Can be fatal in overdose (esp amitriptyline) - cause QTc prolongation and arrhythmia **Can be used at low doses for neuropathic pain
What is Vortioxetine?
-New hot off the press drug -Has all sorts of serotonergic activity (affects various receptors) -Well tolerated: most common SE is nausea -Good evidence base for improvement in difficult to treat cognitive symptoms (concentration and memory) *Reasonable to try this medication if patient has treatment resistant depression and having trialed 2 other antidepressants
What are MAOIs? What is important to remember wrt these drugs and patient safety?
-Monoamine Oxidase inhibitors: MAOI-A work more on serotonin and MOAI B work more on dopamine - increase the amount fo serotonin, dopamine and NA in system -Potential for significant and dangerous interactions with other drugs -Watch out for tyramine reaction leading to hypertensive crisis: avoid cheese, pickled meats, wine and other tyramine products *If changing to another antidepressant need a washout period of up to 6 weeks
What are the practical considerations for dose increases/switching in depression and anxiety?
-If an antidepressant is going to work, it will do so within the first 3 weeks (wait 4 to see effect) -Depression: if an antidepressant has no benefit at a typical dose, its not worth increasing the dose - witch to another. If partial benefit then trial dose increase -Anxiety (esp OCD): consider increasing dose if no initial benefit
What is discontinuation syndrome? Which drugs are hardest to stop?
-Syndrome characterised by sweating, shakes, agitation, insomnia, headaches, irritability, nausea, vomiting, parasthesia, clonus -Influenced by half life: the shorter the half life the bigger the problem - unpleasant but not life-threatening -Paroxetine and Venlafaxine are trickiest to stop (can sometimes cover with fluoxetine)
What is serotonin syndrome?
-Excess serotonin - very vague presentation -Cognitive: headaches, agitation, hypomania, confusion, coma -Autonomic: shivering, sweating, hyperthermia, tachycardia, nausea and diarrhoea -Somatic: myoclonus, hyper-reflex is and tremor -Treatment: usually supportive - fluids and monitoring
What should you consider when starting someone on an antidepressant? What drugs should you use when starting a pt on an antidepressant for the first time?
-What has been used before? Was it effective and/or tolerated? -Think of weight loss, insomnia, neuropathic pain -Compliance: must be on the antidepressant for at least 6-12 after feeling well to prevent recurrence -New cases with no previous tax, start with an SSRI (usually sertraline) unless there is major weight loss or major sleep difficulty (in which case consider Mirtazapine) or comorbid neuropathic pain (SNRI) -If SSRI has no effect, switch to different SSRI, if no effect then switch to SNRI or MIrtazapine
