Psychopharmacology: Antidepressants & Antipsychotics Flashcards
Remind yourself of some conditions antidepressants are used for
- Moderate to severe depression
- Dysthmia
- Anxiety disorders
- OCD
- PTSD
- Eating disorders
- Chronic pain
State the 7 different classes of antidepressants
What route are all antidepressants given via?
Oral
Describe the mechanism of action of SSRIs
State some examples
- Inhibit re-uptake of serotonin into presynaptic neurones to increase the cocentration of serotonin in the synaptic cleft
- Examples:
- Fluoxetine
- Sertraline
- Citalopram
- Escitalopram
- Paroxetine
- Fluvoxamine
Why is fluvoxamine not regulary prescribed anymore?
Cytochrome P450 enzyme inhibitor so commonly interacts with other medications potentating their side effects
State some common side effects of SSRIs
*HINT: categorise your answers into GI side effects, CNS side effects & sexual side efffects
- Nausea
- Flatulence
- Diarrhoea
- Insomnia
- Restlessness
- Irritability
- Agitation
- Tremor
- Headache
- Acute dystonia (uncommon)
- Ejaculatory delay
- Anorgasmia
What are the risks of SSRI use in:
- 1st trimester
- 3rd trimester
- 1st trimester= increased risk of congenital heart defects
- 3rd trimester= increased risk of persistent pulmonary hypertension
What must you also prescribe if someone is taking both an SSRI and an NSAID and why?
PPI e.g. omeprazole as SSRIs increase risk of bleeding in GI tract in particular when combined with NSAIDs
State a contraindication to using an SSRI
- Mania
Cautions include:
- History of mania
- Epilepsy
- Acute angle glaucoma
- Diabetes mellitus (monitor glycaemic control after initiation)
- GI bleeding
- Increased suicide risk in young adults
Give some example doses of common SSRI drugs
*Just so you have an idea
- Sertraline: 50-200mg/day
- Fluoxetine: 20-60mg/day
- Citalopram: 20-40mg/day
- Escitalopram: 10-20mg/day
- Paroxetine: 20-50mg/day
*Citalopram is lowest dose, sertraline is highest. Rest sit roughly between these two doses.
Describe the mechanism of action of SNRIs
State some examples of SNRIs
Prevent reuptake of noradrenaline and serotonin into presynaptic neurone to increase concentration of both in the synaptic cleft
Examples:
- Venlafaxine
- Duloxetine
State some common side effects of SNRIs
- Nausea
- Dry mouth
- Headache
- Dizziness
- Sexual dysfunction
- Hypertension
- Decreased appetite
- Arrhythmias/palpitations
State some contraindications for SNRIs
- Uncontrolled hypertension
Caution with conditions associated with high risk of cardiac arrhythmia. Other cautions similar to SSRIs.
Describe mechanism of action for tricyclic antidepressants
State some examples
Inhibit reuptake of noradrenaline and serotonin into pre-synaptic neurone to increase concentration of both in synaptic cleft. Also have affinity for cholinergic receptors (contributes to side effect profile).
Examples:
- Amitriptyline
- Clomipramine
- Nortriptyline
- Dosulepin
State some common side effects of TCAs
*HINT: group side effects into anticholinergic, cardiovascular, hypersensitivity, psychiatric, metabolic, neurological & others
- Anticholinergic: dry mouth, constipation, urinary retention (which may lead to overflow incontinence), blurred vision
- Cardiovascular: arrhythmias, postural hypotension, syncope
- Hypersensitivity: urticarial, photosensitivity
- Psychiatric: hypomania/mania, delerium or confusion
- Metabolic: increased appetite & weight gain
- Neurological: convulsions, taste disturbances
- Others: headache, sexual dysfunction, tremor
*Key ones to inform pts of: urinary retention, cardiac, convulsions as these are serious/can be problematic
State some contraindications to TCAs
- Arrhythmias (particulary heart block- seek cardiologist input if need to start)
- Mania
- Agranulocytosis
- Severe liver disease
Cautions include: history of epilepsy, cardiac disease, preg & breast feeing, history of main, glaucoma, history urinary retention
Describe the mechanism of action of MAOI
State some examples
Inactivate monoamine oxidase enzymes that oxidize the monoamine neurotransmitters dopamine, noradrenaline, serotonin & tyramine hence increasing availabity of the neurotransmitters.
Examples:
- Moclobemide (reversible)
- Phenelzine (irreversible)
- Isocarboxide (irreversible)
State some common side effects of MAOIs
- GI: constipation, diarrhoea, nausea, hepatotoxicity
- CNS: headahce, parasthesia, dry mouth, postural hypotension
- Hypertensive reactions with tyramine containing foods
Explain why a hypertensive crisis may occur if pt taking MAOI ingests tyramine containing foods
What are the features of a hypertensive crisis?
State some tyramine containing foods
Tryamine, found in some food & drinks, is usually inactivated in body by monoamine oxidases; if taking MAOIs these enzymes are inhibited hence tyramine is not broken down. Tyramine causes the release of noradrenaline which has a pressor effect causing raised BP.
Features: headache, palpitations, fever, convulsions, coma
Few examples of tyramine containing foods:
- Most cheeses
- Some red wines & beer
- Cured & smoked meats
- Marmite
MAOIs interact with certain drugs; state some examples
- SSRIs
- TCAs
- Opiates
- Anti-epileptics
- Insulin
State 2 contraindications to MAOIs
Acute confusional states
Phaeochromocytoma
Mirtazapine is now recongised as a class of its own however used to be called a noradrenaline serotonin specific antidepressant (NASSA), disucss:
- Mechanism of action
- Common side effects
- Who it is ideal for
Alpha-1 and alpha-2 antagonist hence enhances central adrenergic & serotonergic transmission. Also has weak noradrenaline re-uptake inhibiting effect and strong anti-histaminergic properties.
Common side effects:
- Dry mouth
- Nausea
- Diarrhoea/constipation
- Increased appetite and weight gain
- Sedation
- Fatigue
- Insomnia
- Abnormal dreams
- Tremor
Ideal if pt nds to gain weight and suffers from insomia (as although it can cause insomnia it can also aid sleep in some)
How long does it take for antidepressants to have an effect?
Begin to take effect by one week however benefit is usually only clinically detectable at 4-6 weeks (hence tell pts take 4-6 weeks till you start to feel better)
Discuss some key points to consider when deciding which antidepressant to prescribe (9)
- Safety profile: guidelines sugest SSRIs as 1st choice due to safety & effectiveness
- Patient preference
- Prior treatment: if previously used antidepressant and was beneficial should try that; if wasn’t beneficial don’t try it
- Type & severity of depression: use SSRIs first. If SSRI-resistant try SNRIs. If insomnia present or weight gain desired mirtazapine is appropriate.
- Suicidal ideation: if person has suicidal ideation avoid drugs which are toxic overdoses e.g. TCAs, MAOIs
- Age & co-morbidities: SSRI’s safest in elderly. Sertraline safest post-MI
- Drug-drug interactions: may need to avoid blood thinning agents in SSRIs
- Pregnancy & breastfeeding: take caution and use lowest dose. Sertraline safest in preg and breast feeding.
- History of mania: SSRIs usually safest. Avoid TCAs
What is serotonin syndrome?
What are symptoms?
What causes serotonin syndrome?
State clinical features of serotonin syndrome (describe triad)
What is the management?
- Rare, life-threatening syndrome due to excess synaptic serotonin in the CNS that clinically manifests as the triad of neuromuscular excitation, autonomic effects, and altered mental status. Best thought of as spectrum of toxicity. Occurs within mins-hours of taking meds.
- Symptoms:
- Neuromuscular excitation: hypereflexia, myoclonus, tremor
- Altered mental status: agitation, confusion, hypomania, coma
- Autonomic: tachycaradia, hyperthermia, sweating, shivering, nausea, diarrhoea
- Caused by therapeutic use, overdose or drug-drug interactions of serotonergic drugs. Most commonly caused by SSRIs but others (e.g. TCAs, lithium) can cause
- Clinical features:
- Cognitive effects: headache, agitation, confusion, coma
- Autonomic effects: sweating, shivering, hyperthermia, hypertension, tachycardia
- Neuromuscular effects: myoclonus, tremor, hyperreflexia, convulsions
- Management:
- Stop offending drug
- Supportive e.g. fluids, cooling, sedation & intubation & ventilation if necessary
- Medications:
- Mild= benzodiazepines e.g. diazepam
- Moderate to severe= benzodiazepines and cyproheptadine or chlorpromazine
Why are benzodiazepines used in treatment of serotonin syndrome?
Why is cyproheptadine used in treatment of serotonin syndrome?
- Benzodiazepines for agitation & tremor
- Cyproheptadine is an H1 blocking antihistamine, but it also has serotonin receptor blocking activity.
Which antidepressant is drug of choice in children & adolescents?
Fluoxetine
Which antidepressant is drug of choice post MI?
Sertraline
How long after initiation of SSRI should you review pts?
- 2 weeks
- BUT if pt <30yrs age or at increased risk suicide see after 1 week
Which SSRIs should you not prescribe in pts with prolonged QT
- Citalopram
- Escitalopram
Which antidepressants are toxic in overdose and so should be avoided in pts with suicidal ideation?
- TCAs
- MAOIs
You can stop SSRIs suddenly; true or false?
False; if stopping should gradually reduce dose over at least 4 week period (not necessary with fluoxetine).