Antidepressants Flashcards
What are the 3 major classes of antidepressants?
- Tricyclic & related antidepressants (TCAs) - increases 5HT & NA levels
- Selective serotonin reuptake inhibitors (SSRIs) - increases 5HT only
- Monoamine oxidase inhibitors - Increases 5HT, NA & Dop
5HT - Serotonin
What’s another class of Antidepressants?
SNRIs - Venlafaxine, Duloxetine.
What are some examples of Tricyclic antidepressants?
- Amitriptyline & Nortriptyline (used for neuropathic pain)
- Clomipramine
- Dosulepin
- Imipramine (most antimuscarinic effects)
- Lofepramine (liver toxic)
Examples of Tetracyclic antidepressants?
Trazodone & Manserin
Examples of Selective Serotonin reuptake inhibitors (SSRIs)?
- Citalopram
- Escitalopram
- Fluoxetine (licensed in children)
- Paroxetine (high withdrawal symptoms, so have to withdraw over a long period of time)
- Sertraline (safe in unstable angina & M.I)
Examples of Monoamine oxidase inhibitors (MAOIs)?
There are irreversible MAOIs n reversible MAOIS.
Irreversible:
- Phenelzine
- Isocarboxazid
- Tranylcypromine (hypertensive crises risk)
Reversible:
- Moclobemide (no washout period - licensed for social anxiety disorder)
What is a washout period?
The time it takes for it to get washed out of your system
What is the indication for antidepressants?
Effective for moderate to severe depression
Not really used for mild depression. Non-medical therapy are normally used for mild like psychological therapy.
How long does it take for antidepressants to take effect?
2 weeks
After 4 weeks, if there’s no effect, doctors can change the medication.
What’s a sign that the antidepressants are working?
Improvement in sleep
What is a side effect of antidepressants?
Increased potential for agitation, anxiety and suicidal thoughts (paradoxical effects), during the first few weeks of treatment.
Is one antidepressant more effective than another?
No, they have similar efficacy but different side effects.
Which antidepressant is 1st class and why?
SSRIs
Because they are better tolerated and safer in overdose than others.
There’s less sedating.
And fewer antimuscarinic & cardiotoxic effects.
And sertraline is safe in patients with unstable angina or who have recently had a MI.
Why aren’t Tricyclic antidepressants and MAOIs first choice?
Tricyclic:
- Toxicity in overdosage is a problem
- More sedating
- More antimuscarinic & cardiotoxic side effects
MAOIs:
- Dangerous interaction with some foods & drugs
- It’s reserved for use by specialist
Examples of enzyme inhibitors?
- Sodium valproate
- Isoniazid
- Cimetidine
- Ketoconazole
- Fluconazole
- Alcohol (binge drinking)
- Chloramphenicol
- Erythromycin
- Sulfonamides
- Ciprofloxacin
- Omeprazole
- Metronidazole
- Grapefruit juice
Examples of enzyme inducers?
CRAP GPS
- Carbamazepines
- Rifampicin
- Alcohol (chronic)
- Phenytoin
- Griseofulvin
- Phenobarbitone
- Sulphonylureas
- St John Wort
Why is St Johns Wort (Hypericum perforatum) not normally used for depression?
Because it is an enzyme inducer and has lots of drug interactions.
If patient stops taking it, the concentration of interacting drugs may increase, leading to toxicity.
Amount of active ingredient also varies in different preparations.
Can St John wort be sold in public?
Yes, it is a popular remedy on sale to public for mild depression.
What is the management for antidepressants?
- Review patients every 1-2 weeks at the start of treatment
- They take at least 2 weeks to work
- Continue treatment for at least 4 weeks (6 weeks if elderly) before switching due to lack of efficacy.
What must be done during treatment of antidepressants?
If there is partial response, continue for further 2-4 weeks (elderly may take longer to respond).
Take for at least 6 month (12 months in elderly) after remission.
What should be done for patients with recurrent depression?
Patients with history of recurrent depression should receive maintenance treatment for at least 2 years.
How long should patients with generalised anxiety disorder take antidepressants for?
12 months for generalised anxiety disorder because higher risk of relapse.
What is associated with all antidepressants?
Hyponatraemia (salt loss) is associated with ALL types of antidepressants (especially in elderly patients)
Especially with SSRIs
What are the signs of hyponatraemia - salt loss?
- Stupor / coma
- Anorexia
- Lethargy
- Tendon reflexes (decreased)
- Limp muscles (weaknesses)
- Orthostatic hypotension
- Seizures/headaches
- Stomach cramps
What is an uncommon adverse drug reaction mainly with SSRIs & SNRIs? And when does it occur?
Serotonin syndrome.
It occurs when serotonin levels are too high. Especially with drugs that raise serotonin.
When does serotonin syndrome symptoms occur?
Symptoms occur days or hours after initiation, dose increase, overdose of serotogenic drug, addition of new drug, or replacement of one drug without allowing enough washout period in between (esp if 1st drug is irreversible MAOI or a drug with a long half life).
When can severe toxicity of Serotonin Syndrome occur?
Can occur with combination of serotogenic drugs, one of which is an MAOI
What are the symptoms of Antidepressants?
- Neuromuscular hyperactivity: tremor, hyperreflexia, clonus, myoclonus (muscle spasm), rigidity
- Autonomic dysfunction: Tachycardia, blood pressure changes, hyperthermia, diaphoresis (sweating), shivering, diarrhoea
- Altered mental state: agitation, confusion, mania
Withdraw medication if symptoms occur
What should be done if there’s no response to treatment?
Increase dose OR switch to different SSRI OR mirtazapine, if initial response to SSRI fails
What are some second line choices for antidepressants?
- Lofepramine
- Moclobemide
- Reboxetine
Venlafaxine (SNRI) - reserved for more severe cases
MAOI requires specialist supervision
What are the third line options for antidepressants?
Add another antidepressant class
OR
Lithium/antipsychotic
