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Medscape Update on St John's Wort

St. John's Wort: A Mini-Review of its Pharmacokinetics and Anti-Depressant Effects
Perry V. Halushka
Posted: 12/16/2009


GENERAL
Hypericum perforatum
yellow flower
long and rich history
originally harvested for the feast of St. John the Baptist
‘wort’ is the Old English name for plant

CONSTITUENTS
naphthodianthrones: of which hypericin, pseudohypericin, and hyperforin
component considered most responsible for beneficial effects on depression is hyperforin
are the most relevant biologically active compounds
also contains quercetin, flavones and xanthoids
many preparations are standardized to the hypericin or pseudohypericin content
amount of active ingredients varies by source, harvest time, plant part used, prep

ACTIVE CONTENTS HIGHLY VARIABLE IN COMMERCIAL PRODUCTS
one study analyzed the total naphthodianthrone content of 54 commercially available preparations of St. John's wort; amount varied from 0% to 109% for capsules and from 31% to 80% for tablets

MECHANISMS
hypericin and hyperforin inhibit uptake of serotonin, dopamine, norepinephrine into synaptosomes
chronic tx of rats-->up-regulation of post-synaptic 5-HT1A and 5-HT2A receptors
hypericin also active at D3 and D4 dopamine receptors
induces hepatic CYPs: CYP3A4, CYP2C9, and CYP1A2
hyperforin induces CYP3A4 via activation of pregnane X, an orphan nuclear receptor
(see original link for more drugs that induce CYPs)

DRUG INTERACTIONS
reduces cyclosporine levels-->heart transplant rejection, increased metabolism of OCPs
can induce expression of the drug transport protein: P-glycoprotein
-->increased efflux of digoxin into the intestinal lumen
-->significant decrease in its AUC and Cmax
can inhibit the activity of sulfotransferases, specifically SULT1A3
-->increased bioavailability for those drugs
(ex: ritodrine) that are metabolized by it in the intestinal epithelium.

EFFICACY IN TX OF DEPRESSION
popular
scientific results are variable, prob dt variable content of active components
not enough double-blinded placebo-controleld trials
meta-analysis of existing science reveals this info:
as effective as SSRIs and more efficacious than placebos
not uniformly effective in major depressive disorders
with the exception of its effects on drug transport and metabolism, few side effects
mc SEs: headache, dry mouth, nausea, gastrointestinal upset and sleepiness
rare side effect: photosensitivity

CAUTION
many pts take St JW without consulting anyone
they are susceptible to the drug interaction issues
pts on SSRI's that add St JW may risk serotonin syndrome
sx of ser synd: lack of coordination, hyperreflexia, agitation, coma, confusion,
tremor, fever, nausea and diarrhea

References
1. http://nccam.nih.gov/
2. Draves AH and Walker SE: Analysis of the hypericin and pseudohypericin content of commercially available St. John’s wort preparations. Canadian J Clin Pharmacol 10:114-118, 2003 [PMID: 14506510]
3. De Smet, PA: Herbal Remedies. New Engl J Med 347:2046-2055, 2002. [PMID: 12490687]
4. Henderson L, Yue QY, Bergquist C, et al: St. John’s wort (Hypericum perforatum): drug interactions and clinical outcomes. Br J Clin Pharmacol 54:349-356,2002 [PMID: 12392581]
5. Linde, K, Berner, MM, Kriston, L: St. John’s wort for major depression. Cochrane Database of Systematic Reviews 2008, Issue 4. Art. No: CD000448. DOI: 10.1002/14651858.CD000448.pub3. [PMID: 18843608]

SOURCE
http://www.medscape.com/viewarticle/713605?src=mp&spon=12&uac=89474MT

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