|
|
Polygonum multiflorum* | |
|
Panax ginseng* | |
|
Henbane* | |
| Side effect reduction/prevention |
None known |
| Reduced drug absorption/bioavailability |
None known |
An asterisk (*) next to an item in the summary indicates that the interaction is supported only by weak, fragmentary, and/or contradictory scientific evidence.
Korean or Chinese ginseng (Panax ginseng)
Laboratory studies have shown that compounds found in Panax ginseng enhance the ability of
phenylephrine to constrict blood vessels.1 Controlled studies are necessary to
determine whether taking Panax ginseng at the same time as phenylephrine will enhance the
beneficial effects of the drug.
Polygonum
multiflorum*
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.2 Controlled
studies are needed to determine whether Polygonum multiflorum helps people with high
blood pressure and whether phenylephrine blocks its beneficial effects.
Henbane (Hyoscyamus niger)
Antihistamines, including chlorpheniramine, can cause “anticholinergic” side
effects such as dryness of mouth and heart palpitations. Henbane also has anticholinergic
activity and side effects. Therefore, use of henbane with chlorpheniramine could increase the
risk of anticholinergic side effects,3 though apparently no interactions have yet
been reported. Henbane should not be taken except by prescription from a physician trained in
its use, as it is extremely toxic.
Alcohol
Drinking alcoholic beverages together with antihistamines can enhance side effects such as
drowsiness and dizziness.4 Consequently, people who are taking pyrilamine and
chlorpheniramine should avoid alcohol, especially when staying alert is necessary.
1. Kwan CY. Vascular effects of selected antiphypertensive drugs derived from traditional medicinal herbs. Clin Exp Pharmacol Physiol 1995;22 Suppl 1:S297–9.
2. 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.
3. Blumenthal M, ed. The Complete German Commission E Monographs. Austin, TX: American Botanical Council, 1998, 146.
4. Olin BR, ed. Respiratory Drugs, Antihistamines. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, 1993, 964–79.
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