Sertraline vs citalopram: two common SSRI antidepressants compared

Both medicines are SSRIs. The NHS says they are thought to work by increasing the level of serotonin, a chemical in the brain linked to mood. The NHS also says that all types of antidepressant generally work as well as each other for depression, but that there are differences in who can take them and in the side effects. That is also true within a class: individual medicines suit different people.

Both take time. The NHS says antidepressants usually take 1 to 2 weeks to start having an effect and can take up to 8 weeks to work fully. Doctors usually start with a low dose and increase it, to reduce the chance of side effects.

The NHS says sertraline can be used for depression, obsessive compulsive disorder (OCD), panic disorder, post-traumatic stress disorder (PTSD) and social anxiety disorder. Citalopram is described as used to treat depression and panic disorder.

This difference in the range of conditions is one reason a prescriber might choose one over the other. If you have OCD or PTSD, for example, sertraline is named by the NHS for these and citalopram is not.

Common side effects overlap: headache, sickness, dry mouth, diarrhoea, sleep problems and sexual problems appear in both lists. Most ease within a couple of weeks. Sertraline adds dizziness or drowsiness and weight gain to the NHS list; citalopram lists sweating, palpitations and constipation. These are not a ranking, since individual experience varies widely.

Serious effects named include allergic reaction, serotonin syndrome and very low mood with suicidal thoughts for both, mania for sertraline, and internal bleeding signs (such as bruises or blood in urine, stool or vomit) for citalopram. For citalopram the NHS also lists a rare, life-threatening heart rhythm problem called torsades de pointes with symptoms of fast irregular heartbeat, light-headedness and fainting, which is why it may not be suitable if you have a heart rhythm condition. The NHS says to speak to a doctor straight away if you have suicidal thoughts when starting an antidepressant.

Both are listed as not mixing well with anti-inflammatory painkillers (NSAIDs), anticoagulants such as warfarin, and MAOI antidepressants, and the herbal supplement St John's wort should not be used with either. For citalopram the NHS also lists sumatriptan, strong painkillers such as tramadol and buprenorphine, and medicines to reduce stomach acid such as omeprazole and esomeprazole. Always tell the prescriber and pharmacist about everything you take.

The NHS says either can be used during pregnancy if needed, with the lowest possible effective dose, and that you may be advised to give birth in hospital so you and your baby can be closely monitored. Both can be used while breastfeeding, though it is best to check. For stopping, your doctor will gradually reduce the dose over several weeks or months for sertraline and over a few weeks for citalopram. Do not stop suddenly.