Melatonin - Valium (Diazepam) Interaction
Herbal: Melatonin
Also Known As: N-Acetyl-5-Methoxytryptamine
Drug: Diazepam
Brand names:
Valium, Valium injection, Diastat AcuDial, Valtoco

Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Apr 27, 2025
Interaction Details
Diazepam is classified as belonging to the following category: Cns Depressants
Theoretically, taking melatonin might increase the sedative effects of CNS depressants.
Melatonin has sedative effects. Theoretically, concomitant use of melatonin with alcohol, benzodiazepines, or other sedative drugs might cause additive sedation.
Interaction Rating
Likelihood of Occurrence
PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
Pharmacist Analysis
Melatonin can interact with drugs that cause sedation or CNS depression, such as benzodiazepines, opioids, and alcohol, leading to additive effects (i.e., additive sedation and drowsiness effects).
This interaction can increase drowsiness and impair cognitive and motor functions, which may be unsafe for activities that require alertness and concentration, such as driving or operating heavy machinery.
However, if you are using melatonin solely for sleep at night, the interaction is generally not of significant concern.
Nevertheless, it is advisable to consult with a healthcare provider before taking melatonin with other medications, especially those that affect the central nervous system.
References
- Foster BC, Cvijovic K, Boon HS, et al. Melatonin Interaction Resulting in Severe Sedation. J Pharm Pharm Sci 2015;18(2):124-31.
Interaction Details
Diazepam is classified as belonging to the following category: Cytochrome P450 1A2 (Cyp1A2) Substrates
Theoretically, melatonin might increase levels of drugs metabolized by CYP1A2. Also, other CYP1A2 substrates might decrease the metabolism of melatonin, increasing melatonin levels.
Melatonin is metabolized in the liver primarily by the CYP2C19 and CYP1A2 enzymes. Theoretically, combined administration of melatonin with drugs metabolized by the CYP1A2 enzyme might reduce the metabolism of these drugs, resulting in increased serum levels. Conversely, some drugs metabolized by CYP1A2 may inhibit the metabolism of melatonin, resulting in increased serum levels of melatonin. Until more is known, use melatonin cautiously in patients taking drugs metabolized by these enzymes.
Interaction Rating
Likelihood of Occurrence
ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
Pharmacist Analysis
Melatonin is metabolized in the liver primarily by the CYP2C19 and CYP1A2 enzymes.
Some studies suggest that melatonin might increase levels of drugs metabolized by CYP1A2. This is because melatonin may inhibit the activity of CYP1A2, leading to reduced metabolism of CYP1A2 substrates and increased serum levels of these drugs.
On the other hand, some drugs metabolized by CYP1A2 may inhibit the metabolism of melatonin, resulting in increased serum levels of melatonin.
Overall, studies suggest that any inhibition of CYP1A2 by melatonin, when used at typical dosages, is likely to be very minor, and clinically significant drug interactions are thought to be unlikely.
- Dr. Brian Staiger, PharmDReferences
- Yeleswaram, K., Vachharajani, N., and Santone, K. Involvement of cytochrome P-450 isozymes in melatonin metabolism and clinical implications. J Pineal Res 1999;26(3):190-191.
- Faber, M. S., Jetter, A., and Fuhr, U. Assessment of CYP1A2 activity in clinical practice: why, how, and when? Basic Clin Pharmacol Toxicol. 2005;97(3):125-134.
- Foster BC, Cvijovic K, Boon HS, et al. Melatonin Interaction Resulting in Severe Sedation. J Pharm Pharm Sci 2015;18(2):124-31.
Interaction Details
Diazepam is classified as belonging to the following category: Cytochrome P450 2C19 (Cyp2C19) Substrates
Theoretically, melatonin might increase levels of drugs metabolized by CYP2C19. Also, other CYP2C19 substrates might decrease the metabolism of melatonin, increasing melatonin levels.
Melatonin is metabolized in the liver primarily by the CYP2C19 and CYP1A2 enzymes. Theoretically, combined administration of melatonin with certain drugs metabolized by the CYP2C19 enzyme may reduce the metabolism of these drugs, resulting in increased serum levels. Conversely, some drugs metabolized by CYP2C19 may inhibit the metabolism of melatonin, resulting in increased serum levels of melatonin. Until more is known, use melatonin cautiously in patients taking drugs metabolized by these enzymes.
Interaction Rating
Likelihood of Occurrence
ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
References
- Yeleswaram, K., Vachharajani, N., and Santone, K. Involvement of cytochrome P-450 isozymes in melatonin metabolism and clinical implications. J Pineal Res 1999;26(3):190-191.
- Faber, M. S., Jetter, A., and Fuhr, U. Assessment of CYP1A2 activity in clinical practice: why, how, and when? Basic Clin Pharmacol Toxicol. 2005;97(3):125-134.
Interaction Details
Diazepam is classified as belonging to the following category: Cytochrome P450 3A4 (Cyp3A4) Substrates
Theoretically, melatonin might increase levels of drugs metabolized by CYP3A4.
Laboratory research shows that certain lots of melatonin inhibit CYP3A4. Theoretically, combined administration of melatonin with certain drugs metabolized by CYP3A4 may reduce the metabolism of these drugs, resulting in increased serum levels. Until more is known, use melatonin cautiously in patients taking drugs metabolized by these enzymes.
Interaction Rating
Likelihood of Occurrence
PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
References
- Foster BC, Cvijovic K, Boon HS, et al. Melatonin Interaction Resulting in Severe Sedation. J Pharm Pharm Sci 2015;18(2):124-31.
Interaction Details
Diazepam is classified as belonging to the following category: Anticonvulsants
Theoretically, melatonin may reduce the effects of anticonvulsants. Some clinical research suggests that melatonin may increase the frequency of seizures in certain patients, particularly children with neurological impairment.
Interaction Rating
Likelihood of Occurrence
PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
References
- Sheldon SH. Pro-convulsant effects of oral melatonin in neurologically disabled children. Lancet 1998;351:1254.
- Stewart LS. Endogenous melatonin and epileptogenesis: facts and hypothesis. Int J Neurosci 2001;107:77-85..
Melatonin Overview

Diazepam Overview
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Diazepam is used to relieve anxiety and to control agitation caused by alcohol withdrawal. It is also used along with other medications to control muscle spasms and spasticity caused by certain neurological disorders such as cerebral palsy (condition that causes difficulty with movement and balance), paraplegia (inability to move parts of the body), athetosis (abnormal muscle contractions), and stiff-man syndrome (a rare disorder with muscle rigidity and stiffness). Diazepam is also used along with other medications to control seizures. Diazepam is in a class of medications called benzodiazepines. It works by calming abnormal overactivity in the brain.
Melatonin - More Interactions
Melatonin interacts with 1425 drugs
Interaction Rating Key
These severity listings are for informational use only. Never start, stop or otherwise change your therapy before speaking with your provider.
Major | The combined use of these agents is strongly discouraged as serious side effects or other negative outcomes could occur. |
Moderate | Use cautiously under the care of a healthcare professional or avoid this combination. A significant interaction or negative outcome could occur. |
Minor | Be aware that there is a chance of an interaction. Watch for warning signs of a potential interaction. |
Unknown | No interactions have been reported or no interaction data is currently available. |
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DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.
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Drug descriptions are provided by MedlinePlus.