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Antidepressants
An oversimplified and commonly understood mechanism of action of all antidepressants is by increasing monoamine availability (serotonin, noradrenaline and dopamine).
| Class | Examples | Clinical features |
|---|---|---|
| Selective serotonin reuptake inhibitor (SSRI) | Sertraline, fluoxetine, citalopram, paroxetine | Better tolerated and lower risk with overdose than TCAs.
Common adverse effects: nausea, GI upset, headache, restlessness, insomnia and sexual dysfunction. |
| Serotonin noradrenaline reuptake inhibitor (SNRI) | Venlafaxine, duloxetine | Duloxetine is also used for chronic pain and urinary incontinence.
Common adverse effects: nausea, GI upset, constipation, insomnia, sexual dysfunction and agitation. |
| Noradrenergic and specific serotonergic antidepressant (NaSSA) | Mirtazapine | Has sedating properties, so useful in patients with insomnia. Common adverse effects: increased appetite and weight gain.Less likely to cause GI upset or sexual dysfunction than SSRIs or SNRIs. |
| Tricyclic antidepressant (TCA) | Amitriptyline, clomipramine | No longer commonly used due to adverse effects (e.g. anticholinergic, postural hypotension, weight gain) and toxicity in overdose. |
| Monoamine oxidase inhibitor (MAOI) | Moclobemide | No longer commonly used due to adverse effects, e.g. hypertensive crisis after ingesting tyramine-rich foods and drug interactions. |
| Serotonin antagonist/reuptake inhibitor | Trazodone | Has sedating properties, so useful in patients with insomnia. |
| Melatonin agonist and specific serotonin antagonist (MaSSA) | Agomelatine (newer) | Liver function needs to be monitored before and during therapy. |
| Over the counter | St John’s wort | Not commonly used due to enzyme induction and the risk of serotonin syndrome. |
Table 1 Common examples of antidepressants by class with key clinical features
References
- Semple D, Smyth R. Oxford handbook of psychiatry. Oxford; New York: Oxford University Press; 2019
- World Health Organization. ICD-11 for Mortality and Morbidity Statistics [Internet]. WHO; 2019 [cited 2022 Mar 12]. Available from: https://icd.who.int/browse11/l-m/en#/http://id.who.int/icd/entity/1707067746
- National Institute of Health and Care Excellence Depression in adults [Internet]. NICE; 2009 [cited 2022 Mar 12]. Available from: https://www.nice.org.uk/guidance/cg90
- MacKinnon D. Depression in adults [Internet]. BMJ Best Practice; 2021 [cited 2022 Mar 12]. Available from: https://bestpractice.bmj.com/topics/en-gb/55
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