Are there any drug interactions between citalopram and sumatriptan?/nBackground: A 51-year-old fema

Fråga: Are there any drug interactions between citalopram and sumatriptan? Background: A 51-year-old female is being treated with citalopram (Cipramil, 20 mg daily). She suffers also from migraines, so she is using sumatriptan (Imigran, dose unknown) occasionally. Adverse effects have not been seen, but the patient is worried about possible interactions after reading the FASS. What is known about the safety of this combination?

Sammanfattning: Possible drug interactions between citalopram and sumatriptan have not been studied. On theoretical grounds, significant interactions are unlikely.

Svar: Very little is known about the possible interaction between citalopram or selective serotonin reuptake inhibitors (SSRIs) in general and sumatriptan. We have done a literature search in Medline and could not find any information on this matter. The indirect warning in FASS is based on theoretical grounds and not on sound experimental or clinical data (1,2).

Sumatriptan activates a subtype of 5-HT-1 receptors (the so called 5-HT-1-like receptor) found in the cranial blood vessels causing these vessels to constrict. This receptor is similar to the 5-HT-1D subtype in the CNS. Co-administration with an SSRI could, therefore, lead to enhanced serotonergic effects due to increased serotonin levels. According to the classification of interactions in the new FASS, this interaction belongs to the A group (probably without any clinical significance).

In the Swedish Adverse Drug Reactions Advisory Committee (SADRAC), there were no reports of adverse drug reactions associated with the use of this combination (3). The manufacturer was not aware of any additional data (4). Both drugs are increasingly used; thus the lack of negative information reflecting that these drugs can be co-administered safely.

There are also some theoretical grounds arguing against significant hazards when combined with the SSRIs. Sumatriptan penetrates the blood-brain-barrier poorly (5) suggesting that additive or synergistic central effects (like the serotonin syndrome (6)) are unlikely. However, peripheral serotonergic effects, like vasoconstriction, could theoretically be more likely. Sumatriptan is metabolized primarily by monoamine oxidase type-A (MAO-A) in the liver (7); hence, metabolic interactions with the different SSRIs are unlikely.

Based on the above argumentation, sumatriptan can be used in the treatment of acute migraine attacks in patients treated also with an SSRI.