Fluvoxamine interaction with other drugs

The most common interactions with SSRIs are pharmacokinetic interactions. For example, paroxetine and fluoxetine are potent CYP2D6 inhibitors (Table 30-4). Thus, administration with 2D6 substrates such as TCAs can lead to dramatic and sometimes unpredictable elevations in the tricyclic drug concentration. The result may be toxicity from the TCA. Similarly, fluvoxamine, a CYP3A4 inhibitor, may elevate the levels of concurrently administered substrates for this enzyme such as diltiazem and induce bradycardia or hypotension. Other SSRIs, such as citalopram and escitalopram, are relatively free of pharmacokinetic interactions. The most serious interaction with the SSRIs are pharmacodynamic interactions with MAOIs that produce a serotonin syndrome (see below). 

Antidepressants are commonly used in combination with antipsychotics to treat depressive symptoms in individuals with schizophrenia. Different antidepressants have been reported to inhibit metabolism of different P450 pathways. Table 66-10 summarizes the potential metabolic drug interactions between antidepressants and SGAs. Potential enzyme inhibitor interactions with clozapine are the most clinically significant. Increased clozapine serum concentrations with a CYP 1A2 inhibitor such as fluvoxamine may precipitate seizures. With the newer atypical antipsychotics, enzyme inhibitors are more likely to cause side effects such as increased sedation, orthostatic hypotension, or increased risk of akathisia and other extrapyramidal side effects. 

The manufacturers of duloxetine contraindicate the concurrent use of MAOIs because of the theoretical risk of the serotonin syndrome. Similarly they recommend caution with other serotonergic drugs, including the SSRIs, venlafaxine, and tryptophan. Fluvoxamine should not be used with duloxetine, because it markedly increases duloxetine levels. Low-dose paroxetine caused a modest increase in the duloxetine ATJC, and fluoxetine is predicted to interact similarly. 

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