Drug-Dietary Supplement Interactions What Have We … · Drug-Dietary Supplement Interactions What...
Transcript of Drug-Dietary Supplement Interactions What Have We … · Drug-Dietary Supplement Interactions What...
Drug-Dietary Supplement Interactions
What Have We Learned?
John S. Markowitz, Pharm.D. 35 min
Professor
University of Florida
Overview
The use of Dietary Supplements in the US
What makes Botanical-Drug Interactions(BDIs)
especially challenging to study?
Basic categorization of drug interactions
Conventional means and limitations of in vivo
assessments
The unique complexities of in vitro BDI
assessment
Conclusions
Drug Interactions with Dietary Supplements The actual prevalence of clinically meaningful
botanical-drug interactions (BDIs) is unknown.
What is known;
~ 50% of all adults in the US report having used at
least one dietary supplement in the past month
and use rates are even higher in in selected patient
populations
~70% do not inform their health care provider of use
and routinely combine supplements with
conventional medications
The estimated number of dietary supplement
products on the market has increased from ~4000 in
1994 to >55,000 in 2012.
Barnes PM and Bloom B (2008) Department of Health and Human Services.
CDC, National Center for Health Statistics. Number 12: December 10, 2008.
The 20 top-selling Herbal Supplements in the US in 2014
HerbalGram. 2015:107;52-59
Medication Categories that Appear to be More
Frequently Associated with BDIs
Tsai H-H, et al. Int J Clin Pract 2012;66:1056–1078
Individual Medications that Appear to be
More Frequently Associated with BDIs
CHALLENGES of BDIs in General:
Unlike conventional agents, dietary
supplements/extracts are complex mixtures
Phenols
Volatile Oils
Flavonoids
Anthocyanins
Tannins
/proanthocyanidins
Isoflavonoids
others
Glucosinilates
Bitters
Saponins
Anthraquinones
Polysaccharides
Coumarins
Macronutrients
lipids, amino acids
Vitamins, minerals
BDI= Botanical Drug Interactions
Individual Botanicals are complex mixtures Goldenseal (Hydrastis canadensis)
Hydrastine
Berberine
Canadine
3′-hydroxy-N,N-
dimethylcoclaurine
1-Demethyl-N,N-
dimethyllincarpine
1,2-Dihydronorreticuline
4′-Demethoxyltembetarine
Magnocurarine
Magnoflorine
N-methylcocluarine
Canelilline
Tembetarine
Stepholidine
Reticuline
Hydrastinine
Isohydrastidine
Scoulerine
Discretamine
20-Hydroxyecdysone
1-Hydroxyhydrastine
Hydrastine methiodine
Dehydrodiscretamine
Canadinic acid
1-Hydroxyhydrastine
Demethyleneberberine
Tetrahydro-jatrorrhizine
13-hydroxyberberine
Jatrorrhizine isomer
Columbamine
Hydrastidine
Thalinfendin
Tetrahydroberberastine
Canadaline
13-Methylcanadine
13-Hydroxycanadine
5,6-Dehydroberberine
13-Methylberberine
13-Methoxyl 5,6-
dehydroberberine
8-Oxotetrahydrothalinfendin
8-Oxotetrahydroberberine
8-Oxoberberine
8-Oxo 5,6-dehydroberberine
Proposed phase I and II metabolism of hydrastine in
humans after administration of Goldenseal Extracts
Gupta PK, et al. DMD 2015;43:534-552
↑
Botanical extracts are often sold as combinations; This further increases the number of potential “perpetrators”
Major Categories of Drug Interactions
Pharmaceutic -e.g. physiochemical incompatibilities: rarely a clinical
issue with botanical supplements
Pharmacodynamic -PD interactions can be additive, antagonistic, synergistic
e.g. the anticoagulant action of warfarin is purportedly enhanced by ginkgo biloba constituents
Pharmacokinetic -Absorption, Distribution, Metabolism (e.g.CYP450), and
Excretion (ADME)
*PK interactions can be the most convincingly demonstrated by drug concentration measurements
Categorizing Drug-Drug Interaction
Significance with Conventional Agents
Major Clinical Significance- relatively well
documented and potentially life threatening
or harmful to patients (these are rare)
Moderate Clinical Significance- more
documentation desirable and potential harm
to the patient is less
Minor Clinical Significance- may occur but
documentation is lacking, potential for harm
is slight, the interaction is rare, or all of the
aforementioned
General Scheme of Drug Metabolism
Estimated contribution of phase I and
phase II enzymes to drug metabolism
What about Drug/Physiological Transporters? Amino acid transporters, LAT SLC7A5 LAT1 (BBB, Placenta), L-DOPA SLC7A8 LAT2 (many tissues), basic and neutral amino acids Bile acid transporter SLC10A1 NTCP (Liver), bile acids SLC10A2 ASBT (ileum), bile acids Peptide transporters, PEP SLC15A1/2 PEPT1/2 (gut/kidney) oligopeptides, ß-lactams Monocarboxylate transporters, MCT SLC16A1 MCT1( gut, BBB etc.) SLC16A7 lactate, benzoate Organic anion transporting polypeptides, OATP SLCO2A1 PGT (lung et al., PG) SLCO1A2 OATP-A, OATP (Brain, anions) SLCO1B1 OATP-C, LST1 (Liver specific) SLCO1B3 OATP-8 (liver specific) SLCO2B1 OATP-B (liver, gut etc.) SLCO3A1 OATP-D (many tissues) SLCO4A1 OATP-E (many tissues) SLCO1C1 OATP-F SLCO4C1 OATP-R (Kidney) digoxin,
Organic ion transporters, OCT, OCTN, OAT SLC22A1 OCT1 (liver, cations, TEA, MPP+) SLC22A2 OCT2 (kidney, TEA, dopamine) SLC22A3 OCT3 (placenta, brain) SLC22A4 OCTN1 (kidney, blood cell, cations) SLC22A5 OCTN2 (kidney etc., carnitine) SLC22A6 OAT1 (kidney, PAH) SLC22A7 OAT2 (liver, PAH, MTX, cAMP) SLC22A8 OAT3 (kidney, PCG, cimetidine) SLC22A OAT4 (placenta, PAH, ochratoxin A) SLC22A OAT5 (liver) SLC22A12 URAT1 (kidney, uric acid) Nucleoside transporter, CNT, ENT SLC28A1,2 CNT1,2 (many tissues), nucleoside concentrative transporters (active) SLC29A1,2 ENT1,2 (many tissues, nucleoside) equilibrium transporters (facilitative) ABC/ATP-dependent transporters ABCA1 Cholesterol ABCB1 P-glycoprotein (many tissues) ABCC1 MRP1 (many tissues, anionic?) ABCC2 MRP2 (liver, gut etc., anions) ABCC3 MRP3 (liver, gut etc., anions) ABCC4 MRP4 (lung etc. antiviral drugs, anions) ABCG2 BCRP(placenta, liver etc. anions)
Zanger & Schwab. Pharmacol Ther 2013
Relative Abundance of CYP450s in Humans
Mechanisms underlying metabolic interactions
between botanical constituents and medications
Brantley SJ, et al. DMD 2014;42:301-17
Choosing Bioassays to Study BDIs
in vivo In the living body, referring to tests conducted in living animals-normal subject studies are ideal. * Animal models, particularly rodents, though relatively inexpensive, have a number of significant translational limitations in the study of DDIs
in vitro In an artificial environment- i.e. test tube or culture media
ex vivo Usually refers to conducting experiments or tests on a tissue(s) taken from a living organism
in vivo Probe Drug or “Cocktail” Methodology
Combinations of “probe” drugs metabolized by specific known
pathways are administered simultaneously to healthy volunteers
both before/after exposure to an agent of interest
* Standard PK parameters (e.g. Cmax, AUC) for the probe drug
and/or metabolite(s) are then calculated pre- and post exposure
* Significance of the results are based upon the magnitude of the
effect, and a substrates potential toxicity at higher Cp (if inhibition)
or consequences of therapeutic failure at lower Cp (if induction)
Examples of Probe Drugs Used: CYP450 Assessed:
dextromethorphan, debrisoquine : CYP2D6
midazolam, dapsone: CYP3A4
caffeine: CYP1A2
mephenytoin, omeprazole: CYP2C19
tolbutamide, diclofenac: CYP2C9
chloroxazone: CYP2E1
Typical “Cocktail” Methodology: CYP3A4 and CYP2D6 Assessing BDIs in Healthy Volunteers
Baseline CYP450 assessments followed
by a minimum 14 day botanical
exposure and then re-assessment is a
typical study paradigm
Research volunteer has consented to photography
Alprazolam Pharmacokinetics: St. John’s wort
The AUC and T1/2 were significantly different at p<0.001. The Cmax and Tmax were not significantly different after SJW treatment.
Alprazolam
PharmacokineticsBaseline After SJW
Cmax (ng/ml) 34 + 9 31 + 7
Tmax (hours) 1.1 + 0.5 1.3 + 0.6
AUC
(ng • hour • ml
-1)
522 + 103 254 + 67
ß1/2 (hour) 12.4 + 3.9 6.0 + 2.4
1
10
100
0 12 24 36 48 60
Time (hours)
Alp
razola
m C
oncentr
ation (
ng/m
l)
Baseline
SJW
After SJW treatment only 7 subjects had
measurable levels of ALPZ at 36 hours, and no
SJW treated subject had measurable levels of
ALPZ at 48 hours.
Markowitz et al, JAMA 2003;290:1500.
Limitations of in vivo (i.e. human) studies
Very expensive to conduct
Protracted time-line for completion e.g. 8hr research unit study day x 2, 14-28 day exposure
periods between study visits, etc
Inter-individual variability in PK
Requisite analytical capability (e.g.LC-MS/MS)
Problems with generalizability of results
Most studies do not include measures of
systemic botanical exposure
Potential risk to Human Subjects
in vitro Tools to Predict Metabolic
Clearance * Liver microsomes
high throughput and most commonly employed
mostly oxidative (e.g. CYP 450)
* S9 fraction • Supernatant fraction obtained from an organ (usually
liver) homogenate by centrifuging at 9000 g x 20 min in a suitable medium; this fraction contains cytosol and microsomes
high throughput
Phase I & Phase II metabolism
* Hepatocytes low throughput
cell membrane/transporters intracellular concentration
Phase I & Phase II metabolism/induction
in vitro Screening for BDIs * Generally Accepted Advantages
High through-put, and may be carried out in most labs
Non-invasive,
Specific mechanism(s) evaluated in controlled system
Potential to identify perpetrating components
In principle, can forecast the magnitude of an intx
Information from enzyme inhibition studies is extremely valuable as it can allow extrapolation of the data to other compounds and of DDIs in organs other than liver.
The availability of human liver tissue, cDNA-expressed CYP enzymes, and specific probe substrates are valuable tools in the assessment of a drug's potential to inhibit different CYP enzymes in vitro.
in vitro Screening for BDIs
* Potential Limitations • In the evaluation of the potency of DDIs, estimation of
the inhibitor concentrations at the target site is essential,
but extremely difficult since its direct measurement is
almost always impossible.
• Does not account for the contribution of first-pass effects, hepatic blood flow, protein binding, non-
hepatic elimination
Unique to Botanical Assessments;
• Some constituents found within plant extracts may not
be absorbed or attain meaningful concentrations
• Metabolites of botanical extracts are poorly
characterized for most extracts and could potentially contribute to the net inhibitory or inductive effects
in vitro Screening for BDIs
• Potential Limitations Unique to Botanical
Assessments Cont….
The commercial availability of many phytochemical is limited which precludes their initial screening using in vitro systems.
(this is improving!)
• There is a known large product to product variability and known difficulties in characterization and standardization of products with complex phytochemical profiles. This may lead to difficulties in reproducibility of experiments
• Confounding physiochemical issues
solubility, stability, purity, solvent effects, buffer effects?
differential contribution of stereoisomers is rarely considered
PROBLEM: In vitro screening studies suggesting BDI
are often not confirmed in clinical confirmatory
studies: e.g. Milk Thistle (Silybum marianum)
In vitro: Concentration-dependent inhibition of CYP2D6, CYP2E1, and CYP3A4 by silymarin and silybin
and mechanism-based inactivation of CYP3A4 and
CYP2C9 by silybins and silymarin extracts have also
been reported
Beckmann-Knopp et al., 2000; Venkataramanan et al., 2000; Zuber et
al., 2002; and Sridar et al., 2004.
In vivo: Formal pharmacokinetic studies in humans have failed to confirm in vitro predictions of metabolic
inhibition
Piscitelli et al., 2002; DiCenzo et al., 2003; Gurley et al., 2004, 2006,
2008; Mills et al., 2005; van Erp et al., 2005; Fuhr et al., 2007; Rao et al.,
2007; Deng et al., 2008; and Kawaguchi-Suzuki et al., 2014
Milk Thistle (Silybum marianum) Extract content vs in vivo disposition
Milk Thistle (Silybum marianum) Extract content vs in vivo disposition
NOTE: Among all evaluated P450 isoenzymes, CYP2C9 appears to be the isoform most
sensitive to inhibition by flavonolignans. In a human liver microsome incubation study, silybin B was determined to be the most potent flavonolignan for the inhibition of CYP2C9 with an IC50 value of 8.2 mM, followed by silybin A (Brantley et al., 2010).
↑ ↑
Analysis of Milk Thistle Capsule (Legalon®)
Silymarin Constituents in Human Plasma 1.5hrs post dose (two 175 mg Legalon® capsules)
LC-MS/MS Analysis of Silymarin Constituents in vitro analysis of Legalon®
capsule
Plasma concentrations 1.5 h after a
single dose (two 175 mg capsules)
J Chromatogr. B 902 (2012) 1– 9
NOTE: In vivo, the Cmax values of free
(unconjugated) silybin A were ~ 2-3-fold
higher than those observed for silybin B, as
well as the much greater AUC0–α and lower
CL/F values for silybin A. This finding is
consistent with the known stereoselective
(i.e. favored) glucuronidation of silybin B* *Jancová et al. Evidence for differences in regioselective and stereoselective glucuronidation of silybin diastereomers from milk thistle (Silybum marianum) by human UDP glucuronosyltransferases. Xenobiotica 2011; 41:743–751.
There are limitations with in vitro testing for BDIs whether testing single or multi-constituent extracts
in vitro studies assessing single
phytoconstituents extracts do not accurately
reflect in vivo exposures does not account for metabolites or co-administered
phytoconstituents when an extract is taken
in vitro studies assessing whole
phytoconstituent extracts will not accurately
reflect in vivo exposures Assumes all constituents in a given extract are
bioavailable and what would be presented to the liver
Overall Summary and Conclusions
A number of limitations should be recognized in the use of in vitro methodologies to assess of BDIs
In spite of these limitations, in vitro methods remain the most powerful and cost-effective tool for initial screening procedures as well as in other applied experiments.
• Semi-quantitative predictions of drug interactions
many unknown factors
human ADME properties in vivo
• Models provide numbers that must be placed in context with multiple factors: therapeutic area, therapeutic index, route of administration
• The relative contribution of stereoisomers should not be ignored in in vitro studies or in bioanalysis.
Acknowledgments
Hao-Jie Zhu, Ph.D.
Xinwen Wang, M.S.
William J. Gurley, Ph.D.
Brian Brinda, Pharm.D.
David I. Appel, MD
Juliana Munoz, Pharm.D.
R21 AT002817-01: “Pharmacokinetics and Drug Interactions with Milk Thistle” NIH National Center for Complementary and Alternative Medicine (NCCAM), Markowitz JS (PI).
Wild Flowers Worth Knowing by Neltje Blanchan (1934)
EXTRA SLIDES
An exploratory ex vivo approach
An exploratory ex vivo approach This study aimed to develop a novel ex vivo approach differing from
conventional in vitro methods in that rather than botanical extracts or
individual constituents being prepared in artificial buffers, human
plasma/serum collected from a limited number of subjects previously
studied was utilized to assess BDIs
METHODS
The clinical samples utilized were sourced from banked residual blood
samples (stored -70 C) from completed normal volunteer PK studies of milk
thistle (MT) extracts and goldenseal (GS).Silybin A, silybin B and hydrastine
and berberine were selected to represent the principal components of MT
and GS, respectively.
Pooled HLMs were pre-incubated with an NADPH generating system in the
presence and absence of various concentrations of the phytoconstituents
in phosphate buffer at 37 C for 10 min.
The reactions for the inhibitory effect assessment of MT and GS were
initiated by adding the probe substrates of CYP2C9 (tolbutamide )and
CYP3A4 (midazolam)
For the ex vivo study, plasma samples containing principal phytochemical
constituents and their metabolites from 5 healthy volunteers who had
participated in PK studies of characterized MT and GS supplements.
ex vivo: Results/Discussion
Compared to conventional in vitro BDI methodologies of assessment, the introduction of human plasma into the in
vitro study model changed the observed inhibitory effect of silybin A and B and hydrastine and berberine on CYP2C9 and CYP3A4/5, respectively, with results which more closely mirrored those generated in clinical study. Data from conventional buffer-based in vitro studies
were actually less predictive than the ex vivo assessments. Thus, this novel ex vivo approach may be a promising approach predicting clinically relevant BDIs than conventional in vitro methods.
Comparison of in vitro and potential value of
ex vivo studies
in vitro Studies with Botanical Supplements
Advantages Limitations
Easy/fast to perform Unknown absorption or bioavailability
Controlled environment Single constituent used
Relatively inexpensive Product-to-product variability=reproducibility problems
Ethical considerations Metabolites poorly characterized=role in DDI
*Results not always confirmed by in vivo studies
ex vivo (plasma) vs in vitro (in buffer) Advantages Limitations
Plasma: all constituents and metabolites in the circulation Time consuming
Clinically relevant concentrations Somewhat more expensive
Endogenous plasma compounds
Involves human subjects although fewer, with a single study phase (no pre- and post exposure),
and much less intense blood sampling
Accounts for protein binding Far less drug analysis
Mean free plasma concentrations of silybin A (A), silybin B (B),
isosilybin A (C), isosilybin B (D) after single oral doses of one (175 mg),
two (350 mg), and three (525 mg) milk thistle extract (Legalon® )
capsules in volunteers (n=13)
Drug Metab Dispos 2013;41:1679-85
Selected Drug Transporters implicated in DDIs of
Interest to the US FDA
FDA Draft Guidance 2012
Non-Agreement of in vitro predictions vs in vivo study Consideration to bioavailability and the potential influence of
stereoselective metabolism