1. PHAR 751 Dietary Effects on Metabolism
Sarah Brown, Pharm.D.
Pharmacy Practice Resident
Asante Health System

2. Metabolism: P-gp review
Substrate + Inhibitor =
Substrate + Inducer =

3. CYP Metabolism Cytochrome P450
Gene superfamily: families subfamilies enzyme
Oxidative metabolism – Phase I
Location
Liver
Small intestine
Most abundant P450 is CYP3A4
Induction =
Inhibition =

4. Metabolism: CYP review
Substrate + Inhibitor =
Substrate + Inducer =

5. Metabolism & Diet
Food
Macronutrients
Protein
CHO
Fats
Micronutrients
Vitamins
Minerals
Indoles
Drink
Grapefruit juice
Orange juice
Seville orange juice
Alcohol
 Diet can alter enzyme activity  influence the intensity & duration of action

6. Macronutrients: Protein Intake
20% of diet
Malnutrition contributes to variability in drug metabolism
CYP-mediated
In rats: CYP3A activity ↓ from 18% to 1% w/ ↓protein intake
CYP1A2 ↓ w/ 0.5% protein diet
CYP1A1: no change

7. Protein intake & theophylline metabolism
CYP-mediated
↓ in Cl of 30% when reduce protein intake from 20% to 10%
↓ t½ from 8-9 h to 6 h by increasing protein from 10% to 40%.
TPN patients  lower plasma Cl

8. Another route of metabolism: FMO1
Flavin-containing monooxygenase (FMO) 1 protein
Oxidative metabolism
Non-inducible
Influenced by dietary intake

9. Micronutrient: Indole effect on metabolism
Indole-3-carbinol (I3C)
Naturally-occurring chemical found in cruciferous vegetables
Induces CYP1A1
Inhibits FMO1
Also marketed as dietary supplement
Katchamart, et al. Concurrent flavin-containing monooxygenase down-regulation and cytochrome p-450 induction by dietary indoles in rat: implications for drug-drug interaction. Drug Metabolism and Disposition 2000; 28 (8): 930 – 936.

10. Influence of dietary I3C on FMO1 protein levels
Four weeks of I3C or DIM in diet of rats
Dose-dependent reduction in liver FMO1 protein levels. Higher dose of I3C, 2500 ppm, reduced levels to 10% that of controls. At same concentration, DIM was more potent, reducing to 3% of control.
Katchamart, et al. Concurrent flavin-containing monooxygenase down-regulation and cytochrome p-450 induction by dietary indoles in rat: implications for drug-drug interaction. Drug Metabolism and Disposition 2000; 28 (8): 930 – 936.

11. FMO (-) and CYP (+)
Dose-dependent inhibition of FMO formation of n-oxide. Not dose dependent: induction of CYP-dependent N-demethylation. Again, DIM, more potent than I3C.
Katchamart, et al. Concurrent flavin-containing monooxygenase down-regulation and cytochrome p-450 induction by dietary indoles in rat: implications for drug-drug interaction. Drug Metabolism and Disposition 2000; 28 (8): 930 – 936.

12. Micronutrient: Indole effect on metabolism of tamoxifen
Dietary I3C reduced N-oxygenation of tamoxifen by liver microsomes without increase in CYP-dependent N-demethylation.
Katchamart, et al. Concurrent flavin-containing monooxygenase down-regulation and cytochrome p-450 induction by dietary indoles in rat: implications for drug-drug interaction. Drug Metabolism and Disposition 2000; 28 (8): 930 – 936.

13. Why do we care? Clinical relevance Drug-drug or drug-food interactions
Potential for altered toxicity of drugs that are substrates for FMO and CYP
Potential altered efficacy (i.e. tamoxifen)
I3C & DIM dietary supplements

14. Alcohol & Tobacco effects on metabolism
80 – 95% alcoholics smoke (25 – 30% non-alcoholics smoke)
70% are heavy smokers
Those who drink & smoke  more cigarettes/day
Correlation between alcohol intake & tobacco use
Association w/ environmental and genetic factors?
Schoedel KA, Tyndale RF. Induction of nicotine-metabolizing CYP2B1 by ethanol and ethanol-metabolizing CYP2E1 by nicotine: summary and implications. Biochimica et Biophysica Acta 1619 (2003) 283– 290.

15. Alcohol & Nicotine: types of tolerance
Cross tolerance
Functional cross-tolerance
Metabolic cross-tolerance
Schoedel KA, Tyndale RF. Induction of nicotine-metabolizing CYP2B1 by ethanol and ethanol-metabolizing CYP2E1 by nicotine: summary and implications. Biochimica et Biophysica Acta 1619 (2003) 283– 290.

16. Alcohol & Nicotine metabolism
Primarily by ADH
20% by CYP2E1 (up to 60% at high BAC)
Nicotine
Metabolized by CYP2A6 (and CYP2B6 in humans; CYP2B1 in rats ) cotinine (inactive)
Schoedel KA, Tyndale RF. Induction of nicotine-metabolizing CYP2B1 by ethanol and ethanol-metabolizing CYP2E1 by nicotine: summary and implications. Biochimica et Biophysica Acta 1619 (2003) 283– 290.

17. CYP2E1 CYP2E1 Also metabolizes APAP, isoniazid, tamoxifen, halothane
Inducible by both EtOH & nicotine
Potential for altering efficacy of clinically used substrates
Schoedel KA, Tyndale RF. Induction of nicotine-metabolizing CYP2B1 by ethanol and ethanol-metabolizing CYP2E1 by nicotine: summary and implications. Biochimica et Biophysica Acta 1619 (2003) 283– 290.

18. Alcohol + Nicotine + CYP2E1 = ?
↑ expression of CYP2E1 (induced by nicotine and EtOH)
↑ metabolism of EtOH = metabolic cross-tolerance
 more EtOH required for same effect = tolerance
Schoedel KA, Tyndale RF. Induction of nicotine-metabolizing CYP2B1 by ethanol and ethanol-metabolizing CYP2E1 by nicotine: summary and implications. Biochimica et Biophysica Acta 1619 (2003) 283– 290.

19. Study in rats Up-regulation of brain CYP2B1 & CYP2E1 by EtOH
 Nicotine metabolized by CYP2B1 = metabolic cross tolerance
Schoedel KA, Tyndale RF. Induction of nicotine-metabolizing CYP2B1 by ethanol and ethanol-metabolizing CYP2E1 by nicotine: summary and implications. Biochimica et Biophysica Acta 1619 (2003) 283– 290.

20. Metabolism & Diet √ Food – protein √ Drink – alcohol
next: citrus juices

21. Flavonoids Naturally occurring in citrus fruits
Known for antioxidant activity
Flavonoids
Flavone
Flavanone
Flavonol
Potential for drug-interactions

22. PK Study: Felodipine & Grapefruit juice
Substrate: felodipine
Enzyme inhibitor: grapefruit juice
Inhibits CYP3A4 & CYP1A2
What happens to felodipine concentrations?
Lown et al. Grapefruit Juice Increases Felodipine Oral Availability in Humans by Decreasing Intestinal CYP3A Protein Expression. J Clin Invest. 1997; 99(19):

23. Naringin A flavonoid Metabolized to the flavonone, naringenin
“bitter” component of grapefruit juice
800 mg/L
~100 g flesh = 200 mL regular strength juice
Inhibits CYP3A4 & CYP1A2

24. Quercetin A Flavonol Average daily intake 16 – 25 mg/day
Adjunct to cisplatin, cyclophosphamide, and adriamycin tx
Chelates metal ions; acts as free radical scavenger
↓ CAD mortality; ↓ stroke incidence
Dietary supplementation: 1 – 1.5 g/day
Known to inhibit oxidation of nifedipine and felodipine

25. Felodipine A dihydropyridine calcium channel blocker
Reversibly competes w/ other CCBs for dhp-binding sites
Blocks voltage-dependent Ca2+ currents in vascular smooth muscle

26. Felodipine + Grapefruit juice
Study: Recurrent administration of grapefruit juice & felodipine kinetics
Hypothesis: continuous administration of grapefruit juice  increased intestinal CYP3A4  diminishing effect on felodipine kinetics
Lown et al. Grapefruit Juice Increases Felodipine Oral Availability in Humans by Decreasing Intestinal CYP3A Protein Expression. J Clin Invest. 1997; 99(19):

27. CYP3A4 concentration in study participants
Drop in the CYP3A4 enterocyte concentration in all subjects
Decreased by 62% fromd D5 to D12. Greater drop in concentration if started at higher concentration
Lown et al. Grapefruit Juice Increases Felodipine Oral Availability in Humans by Decreasing Intestinal CYP3A Protein Expression. J Clin Invest. 1997; 99(19):

28. ↓ CYP3A4 following GFJ administration
Lown et al. Grapefruit Juice Increases Felodipine Oral Availability in Humans by Decreasing Intestinal CYP3A Protein Expression. J Clin Invest. 1997; 99(19):

29. All CYPs? Or just 3A4?
“…no consistent change in the level of enterocyte CYP2D6 or CYP1A1 protein with recurrent grapefruit juice ingestion.”
Lown et al. Grapefruit Juice Increases Felodipine Oral Availability in Humans by Decreasing Intestinal CYP3A Protein Expression. J Clin Invest. 1997; 99(19):

30. Clinical interactions: felodipine & GFJ
∆ = after 5 days GFJ tid
○ = after first glass GFJ
● = Water
With first glass of grapefruit juice: 225% increase in Cmax. Also 116% increase in AUC
Effect does not diminish with continued ingestion – after 16th glass of GFJ, Cmax increased 34% and AUC 44% over respective mean values with initial glass. Magnitude varied considerably among the 10 subjects
Lown et al. Grapefruit Juice Increases Felodipine Oral Availability in Humans by Decreasing Intestinal CYP3A Protein Expression. J Clin Invest. 1997; 99(19):

31. Conclusion: Felodipine + Grapefruit juice
Study: Recurrent administration of grapefruit juice & felodipine kinetics
Hypothesis: continuous administration of grapefruit juice  increased intestinal CYP3A4  diminishing effect on felodipine kinetics
Result: decrease in intestinal CYP3A4 in all subjects
Lown et al. Grapefruit Juice Increases Felodipine Oral Availability in Humans by Decreasing Intestinal CYP3A Protein Expression. J Clin Invest. 1997; 99(19):

32. Thursday’s lecture 3/1/07

33. Terfenadine Second-generation H1-receptor antagonist
Rapidly and almost completely metabolized by CYP3A4
Active metabolite
Cardiotoxic drug-drug interactions w/ erythromycin and ketoconazole
Cardiotoxic effect: repolarization abnormalities  torsades de pointes VTach
Benton, et al. Grapefruit juice alters terfenadine pharmacokinets, resulting in prolonged repolarization on the electrocardiogram. Clin Pharmacol Ther. 1996; 59:

34. PK study: Terfenadine & Grapefruit juice
Study: Is bioavailability of terfenadine enhanced by GFJ?
Does timing of terfenadine dose and administration of GFJ matter?
Benton, et al. Grapefruit juice alters terfenadine pharmacokinets, resulting in prolonged repolarization on the electrocardiogram. Clin Pharmacol Ther. 1996; 59:

35. PK study: Terfenadine & Grapefruit juice
Primary endpoints: QT prolongation, AUC, Cmax, Tmax
60 mg terfenadine bid x 7d
+ 240 mL GFJ w/ terfenadine x 7d
OR mL GFJ 2 h after terfenadine dose x 7 d
EKG and plasma level on day 7 and day 14

36. PK study: Terfenadine & Grapefruit juice
12 healthy people, 60 mg terfenadine q12h. Randomized parallel design
A: Simultaneous GFJ administration B: GFJ 2 hours after terfenadine
Benton, et al. Grapefruit juice alters terfenadine pharmacokinetics, resulting in prolonged repolarization on the electrocardiogram. Clin Pharmacol Ther. 1996; 59:

37. PD: Terfenadine & Grapefruit juice
Simultaneous group: QTC interval is greater at every time point over the dosing interval. After GFJ admin, QTc increased from 420 to 434
Delayed group, NS changes with or w/o GFJ
A: Simultaneous GFJ administration B: GFJ 2 hours after terfenadine
Benton, et al. Grapefruit juice alters terfenadine pharmacokinetics, resulting in prolonged repolarization on the electrocardiogram. Clin Pharmacol Ther. 1996; 59:

38. Benton, et al. Grapefruit juice alters terfenadine pharmacokinetics, resulting in prolonged repolarization on the electrocardiogram. Clin Pharmacol Ther. 1996; 59:

39. PK study: Terfenadine & GFJ conclusions
PK interaction: Increases terfenadine concentration in some subjects
Effect more pronounced when administered together
Delayed effect likely d/t rapid absorption of terfenadine
Interaction occurs in gut wall CYP3A enzymes
↑ concentration  increase in QTc interval on EKG
Take home point: Be aware of interaction b/c every pt is different. May lead to arrhythmia.
Benton, et al. Grapefruit juice alters terfenadine pharmacokinetics, resulting in prolonged repolarization on the electrocardiogram. Clin Pharmacol Ther. 1996; 59:

40. Another study: Felodipine, water, grapefruit juice
PK of IV and PO felodipine
Grapefruit juice or water 15 min prior to dose of felodipine
10 mg ER tablet or 1.5 mg IV over 60 min
Measured SBP, DBP, and HR
12 healthy men w/in 20% of IBW
Lundahl J, Regardh CG, Edgar B, Johnsson G. Effects of grapefruit juice ingestion ± pharmacokinetics and haemodynamics of intravenously and orally administered felodipine in healthy men. Eur J Clin Pharmacol. 1997;52:

41. PK: Felodipine  IV felodipine w/ water IV felodipine w/ GFJ
 PO felodipine w/ GFJ
GFJ  no effect on IV route
PO route: mean increase in Cmax 173%, and increase in AUC 72%. No Tmax or t1/2 change
 PO felodipine w/ water
Lundahl J, Regardh CG, Edgar B, Johnsson G. Effects of grapefruit juice ingestion ± pharmacokinetics and haemodynamics of intravenously and orally administered felodipine in healthy men. Eur J Clin Pharmacol. 1997;52:

42. PK data
Lundahl J, Regardh CG, Edgar B, Johnsson G. Effects of grapefruit juice ingestion ± pharmacokinetics and haemodynamics of intravenously and orally administered felodipine in healthy men. Eur J Clin Pharmacol. 1997;52:

43. Hemodynamic effects in relation to PK
Oral felodipine + GFJ  ↓ DBP (12 – 19 mmHg); ↓ HR
Effects were similar for IV felodipine w/ water & GFJ
Lundahl J, Regardh CG, Edgar B, Johnsson G. Effects of grapefruit juice ingestion ± pharmacokinetics and haemodynamics of intravenously and orally administered felodipine in healthy men. Eur J Clin Pharmacol. 1997;52:

44. Hemodynamic data

45. Study: Felodipine & GFJ conclusions
Metabolism of felodipine occurred in gut wall
Increased plasma concentrations w/ oral felodipine & GFJ  increase hemodynamic effects

46. Clinical Application
GFJ: ↑ oral availability of commonly used medications
Is the interaction significant?

48. Grapefruit juice & Seville Orange juice
Furocoumarins
Bergamottin (16 μM GFJ; 5 μM SOJ)
6’,7’-dihyroxybergamottin (10-60 (23) μM GFJ; 36 μM SOJ)
Bergapten (31 μM SOJ only)
Bergapten – less potent 6’7’ dihydroxybergamottin

49. Study: Seville Orange juice, GFJ, & felodipine
Juice  equimolar concentration
Single dose felodipine
Seville orange juice
Dilute GFJ
Common orange juice  (-) control
Hypothesis: furocoumarins are involved in the “grapefruit juice interaction”
Equimolar concentrations of bergamottin and 6’,7’-dihydroxybergamottin
5 men, 5 women, 10 mg ER tablet felodipine. 8 oz or 240 mL juice
Malhotra et al. Seville orange juice-felodipine interaction: Comparison with dilute grapefruit juice and involvement of furocoumarins. 2001; 69(1):14-23.

50. Conc vs. time - felodipine
(A- Felodipine) Seville OJ: AUC increased 76%, Cmax increased 61%
w/ GFJ: AUC increased 93% and Cmax increased 88% compared to control (OJ). Difference between GFJ and SOJ were NS.
(B – Dehydrofelodipine) AUC increased ~30%, but not Cmax.
Single, inactive primary metabolite, then secondary metabolite by CYP3A4
GFJ interaction decreased metabolite/parent AUC ratio  inhibition of the primary metabolic pathway.
GFJ action through inhibition of CYP3A4 mediated first-pass metabolism in the small intestine.
Malhotra et al. Seville orange juice-felodipine interaction: Comparison with dilute grapefruit juice and involvement of furocoumarins. 2001; 69(1):14-23.

51. PK data: felodipine
PK data following a single dose of felodipine taken with 8 ounces SOJ, GFJ, or OJ
Malhotra et al. Seville orange juice-felodipine interaction: Comparison with dilute grapefruit juice and involvement of furocoumarins. 2001; 69(1):14-23.

52. Study conclusions
Sufficient bergamottin and 6’,7’-dihydroxybergamottin concentrations
 drug-interaction
More furocoumarins?
 drug-interactions
Sufficient conc. To produce in vivo inhibition of CYP3A4 and interaction with felodipine

53. Just in case…
Cyclosporine: Edwards et al. 6’,7’-dihydroxybergamottin in grapefruit juice and Seville orange juice: Effects on cyclosporine disposition, enterocyte CYP3A4, and P-glycoprotein. Clin Pharmacol Ther 1999;65(3):
Pranidipine: Hashimoto et al. Interaction of citrus juices with pranidipine, a new 1,4-dihydropyridine calcium antagonist, in healthy subjects. Eur J Clin Pharmacol 1998;54:
Celiprolol: Lilja JJ, Juntti-Patinen L, Neuvonen PJ. Orange juice substantially reduces the bioavailability of the β-adrenergic-blocking agent celiprolol. Clin Pharmacol Ther 2004;75(3):
Fexofenadine: Dresser et al. Fruit juices inhibit organic anion transporting polypeptide-mediated drug uptake to decrease the oral availability of fexofenadine. Clin Pharmacol Ther 2002;71(1):11-20.

55. St John’s Wort OTC: Treat anxiety, depression, sleep disorders
Warning on antiretroviral drugs d/t decreasing drug concentration w/ St John’s wort

56. St John’s Wort Known CYP3A4 induction Reports of interactions with:
Theophylline (CYP1A2)
Amitriptyline ((CYP2D6, CYP1A2)
Warfarin (CYP2C9)
Digoxin (p-gp substrate)
Wang et al. The effects of St John’s wort (Hypericum perforatum) on human cytochrome P450 activity. Clin Pharmacol Ther 2001;70(4):

57. PK study: St John’s wort & CYP
Interaction at the level of CYP?
Which CYPs are involved?
Induction? Inhibition?
Three part study (control, short-term dosing, long-term dosing)
Wang et al. The effects of St John’s wort (Hypericum perforatum) on human cytochrome P450 activity. Clin Pharmacol Ther 2001;70(4):

58. Study drugs Tolbutamide (CYP2C9) Caffeine (CYP2A1)
Dextromethorphan (CYP2D6)
Oral midazolam (intestinal wall and hepatic CYP3A)
IV midazolam (hepatic CYP3A)
Wang et al. The effects of St John’s wort (Hypericum perforatum) on human cytochrome P450 activity. Clin Pharmacol Ther 2001;70(4):

59. PK study: St John’s wort & CYP
Control: tolbutamide, caffeine, DM po, and versed IV, then oral versed 24 h later
Short-term: 900mg St John’s wort then same as above, + 2nd dose of 900mg then St John’s wort x additional days
Long-term: 900mg St John’s wort then same as above, + 2nd dose of 900mg

60. PK study: St John’s wort & CYP
IV oral
Short-term: no change
Long-term: 50% reduction in oral AUC and Cmax
□ before St John’s wort
○ after St John’s wort (short-term phase)
♦ after St John’s wort (long-term phase)

61. PK data Short-term: no change
Long-term: 50% reduction in oral AUC and Cmax

62. Study drugs Tolbutamide (CYP2C9) Caffeine (CYP2A1)
Dextromethorphan (CYP2D6)
Oral midazolam (intestinal wall and hepatic CYP3A)
IV midazolam (hepatic CYP3A)
Wang et al. The effects of St John’s wort (Hypericum perforatum) on human cytochrome P450 activity. Clin Pharmacol Ther 2001;70(4):

63. Other outcomes Oral caffeine – CYP1A2  NS
Oral tolbutamide – CYP2C9  NS
Oral DM – CYP2D6  NS
Interaction = CYP3A4

64. Study conclusions Induction of CYP3A by St John’s wort
Long-term use  ↓ efficacy of drugs metabolized by CYP3A
Induction in intestinal wall. >40% of all Rx drugs are metabolized by CYP3A enzymes

65. Lycopene

66. Lycopene ~80% of dietary lycopene from tomatoes and tomato products
Most abundant carotenoid in human plasma
Evidence for beneficial effects  preventing prostate cancer
Availability from tomatoes is improved with processing (puree > raw)
Prevention of prostate cancer. More lycopene intake, decrease risk of developing cancer
Cohn et al. Comparative multiple dose plasma kinetics of lycopene administered in tomato juice, tomato soup or lycopene tablets. Eur J Nutr 2004;43:

67. Lycopene study Lycopene depletion phase
Each group ~20mg lycopene daily x 8d
Three tx groups
Juice
Soup
Tablet
Cohn et al. Comparative multiple dose plasma kinetics of lycopene administered in tomato juice, tomato soup or lycopene tablets. Eur J Nutr 2004;43:

68. Lycopene study
Cohn et al. Comparative multiple dose plasma kinetics of lycopene administered in tomato juice, tomato soup or lycopene tablets. Eur J Nutr 2004;43:

69. Lycopene concentration: juice vs. soup vs. tablet
Cohn et al. Comparative multiple dose plasma kinetics of lycopene administered in tomato juice, tomato soup or lycopene tablets. Eur J Nutr 2004;43:

70. Conclusions Processing releases lycopene for absorption
Also causes conversion to all-E-lycopene, the most stable configuration
8 days of tomato product double the average concentration from baseline