There is considered to be a 'moderate' or 'major' (source dependent) interaction between Vyvanse and Luvox (fluvoxamine), a medication classified as a SSRI (Selective Serotonin Reuptake Inhibitor). In fact, the interaction is considered to be between Vyvanse and all SSRI medications, not just Luvox.

Vyvanse - SSRI Interaction

The use of Vyvanse (lisdexamfetamine) with SSRI medications may increase the risk of a rare but serious side effect known as serotonin syndrome. Although rare, serotonin syndrome is extremely serious and can be fatal in certain situations. Symptoms of serotonin syndrome include:

  • Hyperthermia
  • High blood pressure
  • Spasms
  • Rigidity
  • Sweating
  • Mental status changes

The risk of serotonin syndrome is there based on how both Vyvanse and SSRI drugs work.

How Vyvanse Works

Vyvanse is a stimulant medication, similar to amphetamine and most chemically similar to dextroamphetamine.  it works by stimulating the release of various neurotransmitters including:

  • Norepinephrine
  • Dopamine
  • Serotonin

While the neurotransmitters norepinephrine and dopamine are thought to be released at all doses of amphetamine products, most amphetamines exhibit a relativity weak effect for stimulating release of serotonin. Typically, it takes higher doses to have this effect. However, all doses of amphetamine are thought to act as weak agonist on serotonin receptors (as opposed to stimulating release of serotonin). Overall, most amphetamines are considered to have stronger effects on norepinephrine and dopamine and weaker effects on serotonin.

How SSRI (Selective Serotonin Re-uptake Inhibitors) Work

SSRI medications are thought to work primarily by enhancing of the actions of serotonin by blocking the re-uptake of the neurotransmitter in the brain, increasing levels and over time resulting in an overall increase in the levels of the neurotransmitter available.

Additional Interaction Information

Although serotonin syndrome is well known, as mentioned above, it is generally considered to be rare and uncommon when using usual doses of medication. Issues generally arise when the combination of multiple drugs increasing serotonin are used.

Having said that, combinations are sometimes needed for therapeutic affect of certain disease states (e.g. major depressive disorders, OCD etc...). In situations like these, it is recommended that patients be monitored for symptoms of  serotonin syndrome, especially at the onset of new treatment initiation as well as with dose increases. 

If you are on a low dose of Vyvanse, it may not exhibit a strong serotonergic effect, as discussed above. Due to this, it is not uncommon to see SSRI medications and amphetamines mixed together.

The most prudent thing you can do if you are on a combination of drugs affecting serotonin is to be monitored for signs and symptoms of serotonin syndrome. After consecutive dosing of each medication, you body will reach steady state concentrations of each and dosing at different times of the day will not have much, if any, impact on whether or not serotonin syndrome occurs. Having said that, Luvox (fluvoxamine) specifically is generally recommended to be dosed at bedtime and Vyvanse should be dosed in the morning to avoid issues with insomnia.