Herbal medicines are often administered in combination with drugs for potential benefits of combining herbal medicines and drugs, even while acknowledging the interaction risks.
Pharmacokinetic and Pharmacodynamic Mechanisms
Cases have been published reporting enhanced anticoagulation and bleeding when patients on long-term warfarin therapy also took dan shen herb. [1] Interactions between herbal medicines and drugs can occur and may lead to serious clinical consequences. There are other theoretical interactions indicated by preclinical data. Both pharmacokinetic and/or pharmacodynamic mechanisms can also contribute to these interactions, dependent on the nature of the drug substance.
Duration of the Use of the Herbs
Dan Shen herb extract is widely used for the treatment and prevention of coronary heart disease and some other diseases. Dan Shen herb extract and theophylline are prescribed together to treat patients with asthma in some areas. In human, theophylline with low therapeutic index is mainly metabolized by CYP1A2. In vitro findings have shown that human CYP1A2 is inhibited by the ethyl acetate extract of Dan Shen Herb or Dan Shen pharmaceutical product. Thus, this suggests the possibility of drug interactions between Dan Shen extract and theophylline (CYP1A2 substrate). However, it was found that long-term oral intake of Dan Shen Herb extract does not change the basic pharmacokinetic parameters of theophylline in healthy subjects. Dose adjustment of theophylline thus may not be necessary in patients receiving concomitant therapy with Dan Shen extract. [2]
Components
Dan Shan Herb contains protocatechualdehyde, salvianolic acid B, tanshinone II(A), cryptotanshinone, etc. Some Dan Shen components in the hydrophilic extract depress the absorption of the protocatechualdehyde in rats, on the contrary, enhance the absorption of the salvianolic acid B and depress its elimination rate. The concomitant components in the lipophilic extract might enhance the absorption of cryptotanshinone and its distribution from the centre compartment to the peripheral compartment, and the metabolism to tanshinone II(A). [3]
Thus, the other components present in the extract of Chinese material medica had significant effect on the pharmacokinetics of its 'active components'. These components can exhibit competitive, synergistic, or metabolic effects. Therefore, the traditional Chinese medicine was a complicated system, It should be taken a scientific and holistic view in the research and development processes. [3]
Strong protein (albumin) binding of Dan Shen (50-70%) in serum was found. Salicylate, a chemical, is also strongly bound to albumin; it is also a widely used over-the-counter medicine in the U.S., we studied Danshen-salicylate interaction in vitro. No significant change in free Dan shen concentrations was observed when salicylate concentrations were subtherapeutic (< or = 100 microg/mL).
However, at therapeutic concentrations of salicylate (≥ = 150 microg/mL), free Dan Shen concentrations significantly decreased. On the other hand, Dan Shen potentially displaced salicylate from protein binding, thereby increasing the free salicylate concentration.
Always remember:
- Consult a qualified healthcare professional before combining herbal medicines with conventional drugs.
REFERENCE
[1] Hu Z, et al, Herb-drug interactions: a literature review. Drugs. 2005;65(9):1239-82.
[2] Qiu F, Effect of danshen extract on pharmacokinetics of theophylline in healthy volunteers.Br J Clin Pharmacol. 2008 Feb;65(2):270-4.
[3] Song M, et al, Pharmacokinetic interactions between the main components in the extracts of Salvia miltiorrhiza Bge. in rat Yao Xue Xue Bao. 2007 Mar;42(3):301-7.
[4] Gupta D, et al, Drug-herb interactions: unexpected suppression of free Danshen concentrations by salicylate. J Clin Lab Anal. 2002;16(6):290-4.
