Drug
Diphenhydramine-Phenylephrine
Summary of Interactions with Vitamins, Herbs, & Foods
Negative Interactions
1- Potential Negative Interaction
Diphenhydramine
Henbane
Antihistamines, including diphenhydramine, can cause “anticholinergic” side effects such as dryness of mouth and heart palpitations. Henbane (Hyoscyamus niger) also has anticholinergic activity and side effects. Therefore, use with diphenhydramine could increase the risk of anticholinergic side effects, though apparently no interactions have yet been reported with diphenhydramine and henbane. Henbane should not be taken except by prescription from a physician trained in its use, as it is extremely toxic.
HenbaneDiphenhydramine- Blumenthal M, ed. The Complete German Commission E Monographs. Austin, TX: American Botanical Council, 1998, 146.
Explanation Required
1- Needs Explanation
Diphenhydramine-Phenylephrine
Fo-Ti
This interaction is based on this drug belonging to a drug class. While this drug may differ from the text and references below, drugs within this class work in a similar way and this interaction is applicable to drugs within the same class.
Many drugs used in the treatment of high blood pressure cause relaxation or dilation of blood vessels. Laboratory studies show that emodin, a compound in Polygonum multiflorum, also relaxes blood vessels. However, animal studies reveal that phenylephrine blocks the action of emodin. Controlled studies are needed to determine whether Polygonum multiflorum helps people with high blood pressure and whether phenylephrine blocks its beneficial effects.
Fo-TiDiphenhydramine-Phenylephrine- Huang HC, Lee CR, Chao PD, et al. Vasorelaxant effect of emodin, an anthraquinone from a Chinese herb. Eur J Pharmacol 1991;205:289-94.