Theanine - Benadryl (Diphenhydramine) Interaction

Interaction Details

Diphenhydramine is classified as belonging to the following category: Cns Depressants

Theoretically, theanine might have additive sedative effects when used in conjunction with CNS depressants. However, it is unclear if this concern is clinically relevant.
Theoretically, theanine may compete with glutamate and/or increase plasma gamma-aminobutyric acid (GABA) levels, which could cause CNS depression. In one clinical study, some subjects taking oral theanine reported drowsiness.

Interaction Rating

Likelihood of Occurrence

Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Pharmacist Analysis

L-theanine is most commonly taken to help improve some aspects of cognitive function. However, it is also sometimes used to treat anxiety and reduce stress as it may have a mild sedative effect. Studies are lacking, but some report theanine's anti-anxiety effects might be due to its effects on glutamate receptors and possibly an effect on certain inhibitory neurotransmitters like glycine or gamma-aminobutyric acid (GABA).

The sedative effects of L-theanine appear to be relatively mild, but it is important to know if combined with other drugs that may cause sedation as well due to the potentially additive effects.

References

• Hidese S, Ota M, Wakabayashi C, et al. Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study. Acta Neuropsychiatr 2017;29(2):72-9.
• Tsuchiya T, Honda H, Oikawa M, et al. Oral administration of the amino acids cystine and theanine attenuates the adverse events of S-1 adjuvant chemotherapy in gastrointestinal cancer patients. Int J Clin Oncol 2016;21(6):1085-90.

Diphenhydramine Overview

• Diphenhydramine is used to relieve red, irritated, itchy, watery eyes; sneezing; and runny nose caused by hay fever, allergies, or the common cold. Diphenhydramine is also used to relieve cough caused by minor throat or airway irritation. Diphenhydramine is also used to prevent and treat motion sickness, and to treat insomnia (difficulty falling asleep or staying asleep). Diphenhydramine is also used to control abnormal movements in people who have early stage parkinsonian syndrome (a disorder of the nervous system that causes difficulties with movement, muscle control, and balance) or who are experiencing movement problems as a side effect of a medication.

• Diphenhydramine will relieve the symptoms of these conditions but will not treat the cause of the symptoms or speed recovery. Diphenhydramine should not be used to cause sleepiness in children. Diphenhydramine is in a class of medications called antihistamines. It works by blocking the action of histamine, a substance in the body that causes allergic symptoms.

Theanine - More Interactions

Theanine interacts with 557 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.