Herbal / Drug Interactions PHARM 512: Clinical Applications ...

Herbal / Drug Interactions PHARM 512: Clinical Applications ...

Table 1. Enrollees in CHS Study a Total enrolled: 5849 White: 4925 (84) Black: 924 (16) Male: 2478 (42) Female: 3371 (58) Study period 1 2 3 Total users 4373 4351

3919 Rx users 3994 (91) 3891 (89) 3533 (90) CAM users 278 (6) 295 (7) 504 (13) Vitamin/mineral 1713 (39) 1707 (39) 1678 (43) users OTC users 2635 (60) 2720 (63) 2263 (58) Rx plus CAM 238 (5) 243 (6)

411 (11) Rx, CAM, OTC 264 (6) 270 (6.2) 459 (11.7) a The number in parentheses is t he percent of the enrolled Elmer et al. Ann Pharmacother. 2007;40:1617-24. 4 3561 3259 (92) 533 (15) 2081 (58) 2219 (62) 463 (13) 511 (14.4) Steps for Detecting and Advising on Herbal/Drug Interactions Is the patient taking any herbal

supplements? Does the herbal have efficacy for the intended use? Is the product reliable? (i.e.,what are they REALLY taking?) Is the Rx drug one with a narrow therapeutic margin? Evaluation of Herbal/Drug Interactions Speculative or Theoretical e.g. St. Johns Wort and tyramine containing

foods due to MAOI effects or evening primrose oil and risk for bleeds with warfarin In vitro effects e.g. ginkgo and microsomal studies showing inhibition of CYP2C9 In vivo - animal studies e.g. kava and alcohol In vivo - human case reports e.g. ginkgo and warfarin bleeds In vivo - healthy human volunteer studies e.g. indinivir and St. Johns Wort In vivo - clinical studies in patients Important Criteria for Evaluation of a Human Herbal/Drug Interaction Report Reputable standardized product used and carefully described? Product used analyzed for marker compounds? Same batch used throughout study? Doses appropriate?

Steady state study to discern CYP induction? Is observation consistent with known mechanisms of action? Is observation consistent with literature observations? Randomized, placebo controlled human volunteer study with appropriate n? Relative Levels of P450 isozymes in human liver 28% 30% 7% CYP 3A4 CYP2C CYP2D6 CYP1A2

CYP2E1 Other 13% 2% 20% Top 20 Selling Herbals for 2007- Mass Market HerbalGram 2008;78:61-62 Product M $ % change rank in 2006 1. soy 25 -17 1 2. cranberry

24 +24 3 3. garlic 20 -13 2 4. ginkgo 18 +12 5 5. saw palmetto 17 - 6 4 6. echinacea 16 - 9 6 7. black cohosh

09 -0.5 8 8. milk thistle 09 -0.4 7 9. ginseng 08 +3 10 10. St. Johns wort 08 -6 9 11. Green tea 05 -7 11 12. Evening primrose oil

04 -9 12 13. valerian 03 -9 13 14. Horny goat weed 02 -2 14 Red indicates risk for drug interactions Top 20 Selling Herbals for 2007- Mass Market HerbalGram 2008;78:61-62 Product 15. bilberry 16. grape seed

17. Yohimbe 18. red clover 19. Horse chestnut seed 20. ginger M $ % change rank in 2004 02 -9 15 02 -9 16 01 -15 17 01 -13 18 01 -21

19 0.7 -20 20 Total (all herbs) 268 +7.6 Red indicates potential risk for drug interactions Note: total herbal sales are estimated at $4.7 billion The above figures include only sales from food stores, drug stores, and mass market retailers but with Wal-Mart figures not included. It does not include warehouse buying clubs (Costco), convenience stores, natural foods stores, multilevel marketers, health professional sales, mail order or internet sales. Stevinson et al. Ann Int Med 133:420-429, 2000 Spontaneous spinal hemoatoma associated with garlic Rose et al. Neurosurgery 1990;26:880-882.

87 year old male 2g of garlic per day for years presented with weakness and partial paralysis bleeding time of 11.5 min (normal = 3 min) day 3 post surgery bleed time of 5 min (after stopping garlic) Other reports: Garlic and TURP bleeding (German et al. Br J Urology 1995;76:518). Garlic and surgery bleeding (Burnham BE; Plastic Reconstr Surgery 1995;95:213). Piscitelli et al. Garlic and Saquinavir. Clin Infect Dis 2002;34:234-238. N=10 Garlic=GarliPure (Natrol)(BID) Piscitelli et al. Garlic and Saquinavir. Clin Infect Dis 2002;34:234-238. N=9 Garlic=GarliPure (Natrol)

(BID) Gurley et al. Clin Pharmacol Ther 2002;72:276-287 n=12; note: used garlic oil prep (500mg TID) Markowitz et al. Clin Pharmacol Ther 2003;74:170, n=14, 3X600mg for 14d (Kwai) Garlic and warfarin Another study showed no effect of aged garlic extract (Kyolic) on patients taking warfarin. HDL went up. No other changes Mecan et al. J. Nutr. 2006;136:793s795s. Garlic summary Efficacy: ? benefit for use in hyperlipidemia. Possible other cardiovascular benefits. Safety: good Drug interactions: warfarin; possibly aspirin and other antiplatelet adhesion drugs

(pharmacodynamic interaction); not with HIV drugs (other 3A4 substrates?) but depends on product (pharmacokinetic interaction) (maybe raw garlic induces 3A4 but not extracts??) Product selection: Suggest enteric coated tablets standardized to about 4mg allicin yield/ tablet Dose: equivalent of about 4g (2-3 cloves) of fresh garlic per day i.e. 8-12 mg allicin/d CYP 1A2 Gurley et al. Clin Pharmacol Ther 2004;76:428-440. CYP 3A4 Gurley et al. Clin Pharmacol Ther 2004;76:428-440. 800mg BID for 30d (Wild Oats Market)(analyzed) Gorski et al. Clin Pharmacol Ther 2004;75:89-100

N=12 crossover, before and after 400mg QID Echinacea purpurea root extract for 8d A= Cl caffeine (CYP 1A2) B= Cl tolbutamide (CYP 2C9) Gorski et al. Clin Pharmacol Ther 2004;75:89-100 N=12 crossover, before and after 400mg QID Echinacea purpurea root extract for 8d Open circle is echinacea A= midazolam IV (CYP 3A4)

B= midazolam PO (CYP 3A4) Echinacea Summary Efficacy: evidence for treatment not prevention Safety: good; rare allergy Drug interactions: Pharmacodynamic: dont give to patients taking immunosuppressive drugs Pharmacokinetic: may inhibit 1A2; may inhibit intestinal 3A4 but induce hepatic so clinical significance unclear; effect on 2C9 is considered minor Product selection: want standardized extract containing about 4% phenolics. (GWE recommends Echinamide in 2008) Dose: about 250mg QID for treatment Questions remaining Which product? Tincture? Tablets? Root extract? Flowering tops? Pressed juice? E. purpurea? E. augusifolia? E. pallida?

Bleeds associated with ginkgo use Patient Ginkgo use age Other therapy Bleed 70 1 week Aspirin Iris

1 78 2 mos Warfarin Intracerebral 2 33 2 years None Subdural

3 61 6 mos None Subarachnoid 4 1. 2. 3. 4. NEJM 336:1108,1997 Neurology 50:1933-1934,1998 Lancet 352:36-37,1998 Neurology 46:1775-1776,1996

ref Ginkgo-warfarin interactions? Non-linear Regression Ki Values Isoform Type of Inhibition Ki (g/ml) CYP1A2 Mixed 11.2

0.6 Competitive 2.1 --- CYP2A6 Mixed 21.2 2.1 CYP2C9 Competitive

9.1 --- CYP2D6 Competitive 133.1 --- CYP3A4 Mixed 17.0 2.5

Mohutsky et al. Am J Ther 2006;13:24-31 Tolbutamide Human Study (CYP 2C9 probe) -6 Subjects (3 males, 3 females) -Subjects ingested 500mg tolbutamide and collected 6-12 hour urine (Control phase) -Followed by a 2 week wash-out period -Subjects then ingested two 60mg Ginkgo biloba extract tablets 2 times a day for 3 days -The morning of day 4 patients received a 500mg dose of tolbutamide along with the ginkgo and collected 6-12 hour total urine (Ginkgo phase) Tolbutamide dose 2 week wash-out period Mohutsky et al. Am J Ther 2006;13:24-31 Ginkgo biloba dose

Tolbutamide dose Comparison of Tolbutamide Metabolic Ratios 1400 1200 1000 800 Control Ginkgo 680 323 610 327 600

Metabolic Ratio (4400 methylhydroxytolbutamide + 200 carboxytolbutamide / tolbutamide) 0 Control Mohutsky et al. Am J Ther 2006;13:24-31 Ginkgo Diclofenac-Ginkgo Interaction (CYP 2C9 probe) 12 healthy non-smoking subjects were recruited (8 males 4 females) 50 mg diclofenac potassium (immediate release) was administered every 12 hours for 14 days On day 8, 120 mg of Ginkgo biloba extract was added to the diclofenac regimen.

On days 7 and 14 plasma collected at times (0, 0.5, 1,2,4,6,8,10, and 12 hrs) 12 hour urine collected Day 7 blood draw Day 14 Blood draw Diclofenac 50 mg every 12 hours Mohutsky et al. Am J Ther 2006;13:24-31 Ginkgo biloba 120 mg every 12 hours Comparison of Diclofenac Clearances from Plasma 1.6 1.4 1.2 1 Control

0.8 0.64 Ginkgo 0.36 0.61 0.33 Cl/F 0.6 (L/hr/kg) 0.4 0.2 0 Control Mohutsky et al. Am J Ther 2006;13:24-31 Ginkgo

Ginkgo biloba - Diclofenac Tolbutamide Human Studies Conclusions No difference was observed in the metabolic ratio between the two arms of the study (tolbutamide alone and tolbutamide + Ginkgo) No difference was seen between the clearances of the two arms of the study ( diclofenac alone and diclofenac + Ginkgo) Ginkgo extract does not appear to interact with CYP2C9 substrates in humans Jiang et al. Br J Clin Pharmacol 2005;59:425-432. N=12 ginkgo for 7d; warfarin alone or in combination with ginkgo or

ginger CoQ10and Ginkgo on Warfarin 3.2 3 2.8 2.6 INR 2.4 2.2 2 CoQ10

Engelsen et al, Thromb Haemost 2002;87:1075-6. N=21,Ginkgo double blind, crossover. Rx=1Placebo month with 2 week washout. Dose of warfarin did not change. Ginkgo and coagulation and pharmacodynamic interactions with antiplatelet adhesion inhibitors Coagulation in healthy adults (in absence of other drugs) Kohler et al. Blood Coagul Fibrinolysis. 2004;15:303-9. (company study). No effect on coagulation parameters in healthy adults after 7d of EGb761 120mg/d. n=50. Gardner et al. Blood Coagul Fibrinolysis 2007;18:287-293 Aspirin 325mg/d for two weeks prior to 4 weeks Ginkgold 300mg/d Bleed times; single dose n=80 cilostazol=Pletel clopidrogrel= Plavix

Ginkgo: Potential Interactions with other drugs (not involving blood coagulation) CYP3A4 Markowitz et al. J Clin Psycopharmacol 2003;23:576-581. No effect of multiple dosing of ginkgo on dextromethorphan (2D6) or alprozolam (3A4) pharmacokinetics. n=12 Study by Gurley and study by Ushida (see slides) Pgp (p-glycoprotein) Mauro et al. Am J Ther 2003;10:247-251. No effect of multiple dosing of ginkgo on digoxin (Pgp) pharmacokinetics. N=8 crossover 2C19 Yin et al. Pharmacogenetics 2004;14:841-850. Small induction of 2C19 mediated hydroxylation of omeprazole. 140mg BID x 12d Gurley et al. Clin Pharmacol Ther 2002;72:276-287 n=12 (CYP 3A4) ginkgo-Wild Oats Markets (24% flavone glycosides, 6% ginkgolides) (analyzed)

Ushida et al. J Clin Pharmcol 2006;46:1290-8 n=12 CYP 3A4 probe is midazolam; note: use Ginkgold 120mg TID! Ginkgo biloba summary Efficacy: good for dementia and poor peripheral circulatory problems Safety: good; rare bleeding episodes Drug interactions: no effect on 3A4,2C9 or 2D6 but may induce 2C19; may inhibit platelet adhesion; possible (not necessarily probable!) interaction with blood thinners and warfarin so avoid or close monitoring needed. Product selection: look for EGb761 extract Dose: 1-2 60mg tabs, BID Questions remaining include

Extent of memory improvement in younger patients? Delay Alzheimers and dementia? Help in other circulatory disorders? Synergistic with other drugs and treatments? Soy and Menopausal and Postmenopausal problems Hot flashes- maybe helps Osteoporosis-some evidence for help Soy Effects on Cancers Long consumption of soy associated with lower rates of breast, endometrial and prostate cancers (Asian cultures) Soy and some soy isoflavones have unknown effects on estrogen receptor positive breast cancer but may stimulate growth Soy may slightly inhibit prostate cancer growth Soy-Cardiovascular Benefits Favorable effects on cholesterol balance; heart healthy Isoflavones inhibit CYP3A4 in vitro

6-hydroxycortisol/cortisol ratio (CYP 3A4) herbal Baseline Week 1 Treatment Treatment Washout Week 2 Week 3 Week 4 Ginseng 4.4 2.4 3.7 2.2 3.6 1.8

3.7 1.6 NS Soy isoflavones 4.9 2.5 5.0 2.0 4.6 2.2 ------- From: Anderson et al., Clin Pharm and Ther 2003;43:643-648 Statistics NS

Soy Efficacy: increased soy ingestion may decrease hot flashes and other postmenopausal symptoms; cardiovascular benefits as well. Safety: good but use in breast cancer may be risky Drug interactions: not with with tamoxifen but effect on CYP3A4 is unlikely Product selection: soy or isoflavones Dose: about 20-40g of soy protein has been used. This contains 30-50mg of isoflavones. Questions remaining include How much benefit? Safety in breast cancer? Probable Interaction Between Warfarin and Ginseng Janetzky and Morreale, Am J. Health-Syst Pharmacy 54:692693,1997

47 yr old male on warfarin for 10 years with an INR of 3-4 started ginseng (INR= 3.1, 4 weeks prev) INR declined to 1.5 after 3 weeks on ginseng INR increased to 3.3 after stopping ginseng causing CYP induction? Changes in individual peak international normalized ratio (INR), INR area under the curve (AUC), peak plasma warfarin level, and warfarin AUC in weeks 1 and 4 in American ginseng or placebo groups Yuan, C.-S. et. al. Ann Intern Med 2004;141:23-27 5mg warfarin for 3d before and after 1g/d ginseng (50mg/d ginsenosides) American ginseng (Panax quinquifolius) n=20 Jiang et al. Br J Clin Pharmacol 2004;57:592-599. SJW, ginseng and placebo in triple crossover study. N=12 single dose 25mg warfarin following 7d (ginseng) or 14d (sjw) of herbal; ginseng dose=54mg/d ginsenosides; Korean ginseng (Panax

ginseng) Jiang et al. Br J Clin Pharmacol 2004;57:592-599. SJW, ginseng and placebo in triple crossover study. N=12 single dose 25mg warfarin following 7d (ginseng) or 14d (sjw) of herbal; ginseng dose=54mg/d ginsenosides; Korean ginseng (Panax ginseng) 6-hydroxycortisol/cortisol ratio (CYP 3A4) herbal Baseline Week 1 Treatment Treatment Washout Week 2 Week 3 Week 4 Statistics

Ginseng 4.4 2.4 3.7 2.2 3.6 1.8 3.7 1.6 NS Soy isoflavones 4.9 2.5 5.0 2.0 4.6 2.2 -------

NS From: Anderson and Elmer, Clinical Pharmacology and Therapeutics 43:643-648 (2003). Gurley et al. Clin Phamcol Ther 2002;72:276-287 n=12; Panax ginseng Ginseng Efficacy: some evidence for applications in geriatric patients (improved quality of life) and in diabetes Safety: good; Drug interactions: no apparent induction of CYP 3A4 but induction of 2C9 (warfarin) with Am ginseng (Panax quinquifolius) but maybe not Panax ginseng. May precipitate hypoglycemia with insulin or oral hypoglycermics. Product selection: product should be

standardized so dose is 4-7% ginsenosides/ d Questions remaining include: What, actually is this stuff good for! Lecrubier et al. Am J Psychiatry 2002;159:1361 n=375 Interactions with St. Johns Wort -cyclosporin Study: 2 case reports case 1: 61yr had transplant 11mos earlier; cyclosporin, azathioprine, steroids for 11 mos. Unexplained heart failure noted after SJW started. case 2: 63yr had transplant 20mos earlier: same senario as case 1. Ref: Ruschitzka et al. Lancet 355:548-549,2000 Markowitz et al. JAMA 290:1500,2003 n=12 14d of SJW CYP 3A4

Durr et al. Clin Pharmacol Ther 2000;68:598-604. Summary of SJW Interactions (adapted from Henderson et al. Br J Clin Pharmacol 2002;54:349-346) Drug HIV protease inhibitors CYP Induce 3A4 Effect Management Stopnd esure virllod (nelfinavir,ritonavor,saquinavir) HIV non-nucleosideR TI (efvirenz,nevirpine) wrfrin

Induce3A4 Induce2C9 orlcontrceptives InducePglycoprotein Induce3A4 nticonvulsnts Induce3A4

digoxin InducePglycoprotein Induce1A2 Increse serotonin Increse serotonin Stopnd esure virllod Stopnddjustwrfrin dose Stopnddjust

cyclosporinedose Stopnduselternte irthcontrol Stopnddjust nticonvulsntdose Stopnddjustdigoxin dose Stopnddjust theophyllinedose Stop Stop cyclosporin theophylline Triptns (su triptn)

SSR I (fluoxetine,sertrline,etc) St. Johns Wort Summary Efficacy: good evidence for mild to moderate depression Safety: dont combine with other medications unless under close monitoring; possible photosensitivity Drug interactions: a problem! Is a broad spectrum P450 inducer and a pglycoprotein inducer. Product selection: want standardized extract containing about 0.3% hypericin or 1-2% hyperforin

Dose: about 300mg TID for treatment Questions remaining include How best to use this herbal given that there are drug interaction problems Potential Interactions of Goldenseal with CYP2D6 and CYP 3A4 substrates Gurley et al. Clin Pharmacol Ther 2005;77:415-426. N=12 Herbals affecting clotting adapted from Natural Medicine Comprehensive Database and Norred and Brinker, Alt Ther Health Med 2001;7:58-67. Andrographis panucula Bogbean Devil claw ginseng

Pau darco angelica Boldo Dong quai green tea meadow sweet anise capsicum Erigeron hawthorn

prickly ash arnica celery Evening primrose oil horse chestnut bark passionflower Asafoeta chamomile feverfew Huang qi

popular Baikal skullcap clove oil fish oil horseradish quassia Bilberry coleus root fenugreek kava

red clover Black current seed danshen garlic licorice reishi mushroom Bladderwrack dandelion root ginger onion

Sha shen Bomelain Danshen ginkgo papain Shinpi bark Sweet birch oil Tonka bean turmeric vitamin E

wintergreen oil wild carrot wild lettuce willow wood ear mushroom woodruff Herbs with clotting problems reported in humans Ginkgo and garlic and St. Johns wort- see earlier notes Evening primrose oil - human study showed 40% increase in bleed time but no other reports

Borage seed oil - same as evening primrose oil Vitamin E - doses >1200 i.u./d can increase bleed time Cranberry juice case reports of increased INR (salicylic acid? CYP 2C9 inhibition?) but in vivo study showed no change in flurbiprofen (CYP 2C9 substrate) in vivo Lycium barbarum case report of increased INR Danshen -

case reports of increased INR with warfarin Dong quai - case reports of increased INR with warfarin American Ginseng - decreased INR with warfarin (Panax quinquifolius) Green tea - case report of decreased INR with warfarin but huge amount CoQ10 - case reports of decreased INR with warfarin but human study showed no effect on INR Glucosamine-

increased INR cases with warfarin Chondroitin- increased INR cases with warfarin Fig. 1 Patient INR Values Tea Taken 5 7/27 4 3 1/12/00 12/15/99

2/16 6/30 4/5 2 value 11/10 INR 8/29 8/2 8/7 5/26 9/7 10/8 8/18

11/7 1 0 10/17 /9 9 12/6 1/25 /0 0 3/15 5/4 Date 6/23 8/12

10/1 From: Lam AY, Mohutsky MA and Elmer GW. Probable herbal/drug interaction between warfarin and a common Chinese herb, Lycium barbarum. Ann Pharmacother 2001;35:11991201 11/20 Table 4a Significant Risk of CAM-drug Adverse Interaction n=5052 (16,173 interviews) Potential Event Mechanisma Numberb Occurrencesc no. patients all occurrences

147 214 Risk of bleeds Aspirin Garlic23;25-27 Ginkgo24;28 PD PD 102 127 Warfarin Garlic25-27

PD 13 16 Ginkgo29 PD 7 7 Ginseng32;33 PKd 3

3 Garlic23;25-27 PD 4 6 Ginkgo24;30;31;54 PD 2 3 PD

3 3 Ticlopidine Pentoxifylline Ginkgo24;30;31 Total 281 (5.6%) 380 Table 4b Significant Risk of CAM-drug Adverse Interaction Numberb Occurrencesc

PKe 2 2 PKf 2 2 PKf 4 5 PD PD

3 2 3 2 Grand Total 294 393 Garlic interactions: Ginkgo interactions: Garlic plus ginkgo: 168 114 282 (96%)

241 140 381 (97%) Potential Event Mechanisma Decreased drug benefit Digoxin St. Johns wort21;34 Felodipine St. Johns wort21;52 Tamoxifen Garlic41 Other Furosemide/Aloe55 Thyroid/Kelp56

Elmer et al. Ann Pharmacother 2007;41:1617-1624 Seem to have low pharmacokinetic drug interaction potential based on recent studies Ginger Valerian Milk thistle Saw palmetto Black cohosh CoQ10

glucosamine Glucosamine and type 2 diabetics study examined the effect of 90d of Cosamin DS or placebo on glycosylated hemoglobin levels in type 2 diabetics. N=38 result: no effect Arch Intern Med 2003;163:1587-90 Knudsen J, Sokol GH. Potential glucosamine-warfarin interaction resulting in increased international normalized ratio: Case report and review of the literature and MedWatch database. Pharmacotherapy 2008;28:540-8. several cases plus 20 reports from FDA MedWatch database. Increased INR on warfarin plus glucosamine or glucosamine/chondroitin Herbals affecting drug management (i.e.,

herbal/drug interactions) literature analysis (Fugh-Berman and Ernst, Herbal Drug Interactions and Assessment of Reliability Br J Clin Pharmacol 2001;52:587-595) 108 reported cases of suspected interactions 69% unable to be evaluated 19% possible interactions 13% (14) well documented 11/14 involved warfarin 7/14 involved St. Johns wort Top 20 Selling Herbals for 2007- Mass Market HerbalGram 2008;78:61-62 Product 1. soy 2. cranberry 3. garlic

4. ginkgo 5. saw palmetto 6. echinacea 7. black cohosh 8. milk thistle 9. ginseng 10. St. Johns wort

11. Green tea 12. Evening primrose oil 13. valerian 14. Horny goat weed Possible interaction may block action of tamoxifen product dependent Inhibition of 3A4; enhance warfarin effect may increase bleed risk; may induce 2C19 may inhibit CYP 1A2 weak 2D6 induction action (?) Panax quiquifolius may induce 2C9 definitive interactions; induce 3A4, other CYP and Pgp may enhance warfarin effect enhance warfarin effect and increase BP Red indicates risk for drug interactions

Top 20 Selling Herbals for 2007- Mass Market HerbalGram 2008;78:61-62 Product 15. bilberry 16. grape seed 17. Yohimbe 18. red clover 19. Horse chestnut seed 20. ginger possible interaction affect BP medications Red indicates potential risk for drug interactions Note: total herbal sales are estimated at $4.7 billion The above figures include only sales from food stores, drug stores, and

mass market retailers but with Wal-Mart figures not included. It does not include warehouse buying clubs (Costco), convenience stores, natural foods stores, multilevel marketers, health professional sales, mail order or internet sales. Gary Elmers assessment of herbal/drug interaction potential (in rank order of significance)(11/13/08) 1. 2. 3. 4. 5. 6. St. Johns wort induces CYP and Pgp; dont take with other drugs unless the drugs have a large therapeutic range and are not life saving drugs

American ginseng (Panax quinquefolius) induces CYP2C9; not with warfarin, tolbutamide and other 2C9 substrates Goldenseal induces CYP3A4 and 2D6. This herbal is not recommended due to lack of efficacy proof and potential interactions Garlic and ginkgo dont take with antiplatelet adhesion drugs or aspirin or with warfarin (risk of bleeds); this is a pharmacodynamic effect. Risk may be over stated based on recent evidence. Ginkgo may induce CYP2C19 so may lower 2C19 substrates Echinacea may induce CYP1A2 so may lower 1A2 substrates References with Good Herbal/Drug Interactions Discussion Top 100 Drug Interactions Hansten PD and Horn JD. H&H Publications 2008 Natural Medicines Comprehensive Database. Online version updated daily. UW Healthlinks http://www.naturaldatabase.com/; $92

Recent Reviews Izzo AA. Herb-drug interactions: an overview of the clinical evidence. Fundam Clin Pharmacol. 2005 Feb;19(1):1-16. Ernst E. Prescribing herbal medications appropriately. J Fam Pract. 2004 Dec;53(12):985-8. Skalli S, Zaid A, Soulaymani R. Drug interactions with herbal medicines. Ther Drug Monit. 2007 Dec;29(6):679-86 Chavez ML, Jordan MA, Chavez PI. Evidence-based drug-herbal interactions.Life Sci. 2006;78:2146-57. What can we do? dialog with NDs and other prescribers recommend the best products ask patients about herbals they may be taking herbals should not usually be recommended for acute or serious illnesses avoid herbal use with drugs with narrow therapeutic window, esp. warfarin, cyclosporin, digoxin, HIV protease inhibitors, theophylline, carbamazepine

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