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Drug Interactions

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Warfarin-cranberry juice interaction.

Posted: 
January 26, 2012
Authors: 
Hamann GL, Campbell JD, George CM
Journal: 
Ann Pharmacother. 45(3):e17
Abstract: 

OBJECTIVE: To report a case of warfarin-cranberry juice interaction, which resulted in an international normalized ratio (INR) elevation on 2 separate occasions.
CASE SUMMARY: A 46-year-old female was receiving a total weekly dose of 56 mg of warfarin. During the 4 months prior to the incident INR, her average INR was 2.0, with a range of 1.6-2.2, while taking the same weekly dose of warfarin. Her INR increased to 4.6 after drinking approximately 1.5 quarts (1420 mL) of cranberry juice cocktail daily for 2 days. Her INR 14 days later without cranberry juice cocktail consumption was 2.3. For the next 3 months, while taking warfarin 56 mg per week, her average INR was 2.1, with a range of 1.4-2.5. At a subsequent visit, after drinking approximately 2 quarts (1893 mL) of cranberry juice cocktail daily for 3-4 days, her INR had increased to 6.5. Her INR after holding warfarin for 3 days was 1.86. Her INR 7 days after resuming the weekly dose of warfarin 56 mg was 3.2. During both of the elevated INR episodes, no other factors were identified that would have resulted in an elevated INR, such as drug, herbal, disease, or other food interactions. An objective causality assessment revealed the interaction was highly probable.
DISCUSSION: Warfarin is the most commonly used anticoagulant for chronic therapy. There have been several case reports of cranberry juice or cranberry sauce potentiating the effects of warfarin by elevating the INR; however, clinical trials evaluating this interaction have failed to demonstrate a significant effect on an INR.
CONCLUSIONS: Our case report describes INR elevations in a patient previously stable on warfarin after ingestion of cranberry juice cocktail daily for several days. This elevation occurred on 2 separate occasions, which distinguishes our case from other published literature.

Cranberry Juice and Warfarin: When Bad Publicity Trumps Science

Posted: 
January 11, 2011
Authors: 
Zikria J, Goldman R, Ansell J
Journal: 
Am J Med 123(5):384-92
Abstract: 

Based on anecdotal reports, the question of whether cranberry juice interacts with warfarin has been raised. This article discusses the potential mechanism, and systematically reviews case reports as well as clinical trials examining the possible interaction. We systematically searched MEDLINE via PubMed, and the Cochrane Library database. Fifteen case reports were summarized, including the initial unpublished brief reports to the Committee on Safety of Medicines and the subsequent 6 published case reports. Seven clinical trials were analyzed, including 3 studies using warfarin and 4 surrogate drugs. Only 2 cases had a validation scale suggesting a "probable" interaction, but even in these patients there were many reasons to question the validity of a relevant drug interaction. Randomized clinical trials and surrogate markers found no evidence to support the interaction between cranberry juice and warfarin. Because the moderate consumption of cranberry juice does not affect anticoagulation, we encourage the reexamination of initial warnings based on scientific evidence. We conclude that the initial precautionary warnings by administrating bodies are limited to anecdotal case reports and represent misleading conclusions.

Warfarin-herb interactions: a review and study based on assessment of clinical case reports in literature

Posted: 
January 11, 2011
Authors: 
Patel JA, Gohil KJ, Garrido G
Journal: 
BLACPMA 7(2):85-99
Abstract: 

The potential risk of herb drug interactions is of particular focus today owing to the increasing and inadvertent use of herbs in recent times. It is a major safety concern for the drugs with narrow therapeutic index like warfarin, a most common anticoagulant with the maximum number of interactions reported. The objective of the present study was to conduct a systemic review of literature to consolidate the clinical case reports of warfarin–herb interactions and to assess the report reliabilities. We reviewed the published clinical literature to consolidate and
assess the interactions between various herbs and warfarin, based on reported adverse events, descriptions of the clinical case reports and case series using electronic databases as well as hand picked references from the year 1971 to year 2007 and ranked them on likely causality
using Naranjo’s algorithm. Out of 72 cases of documented case reports of warfarin with various herbs, 84.7% cases were evaluated as possible interactions (61/72) and 15.3% cases (11/72) as probable interactions. Cranberry juice was most commonly involved in interactions with warfarin with 34.7% of cases (25/72) of which 92% cases were possible interactions (23/25) and 8% cases (2/25) were probable
interactions. Hence, we conclude that combining anticoagulant medicines with herbs appears to be a risky proposition. The number of herbs reported to interact with warfarin continues to expand. Patients on warfarin are specifically advised to avoid taking herbal medicines or to
have their INR measured within two weeks of starting the drug, to be on a safer side. Further, more systematic studies pertaining to warfarin herb interactions are urgently warranted.

Pharmacodynamic interaction of warfarin with cranberry but not with garlic in healthy subjects1

Posted: 
December 17, 2010
Authors: 
Abdul MJM, Jiang X, Williams KM, Day RO, Roufogalis BD, Liauw WS, Xu H, McLachlan AJ.
Journal: 
Br J Pharmacol 154(8):1691-1700
Abstract: 

Background and purpose: Patients commonly take complementary medicines in conjunction with warfarin yet evidence supporting the safety or the risk of a herb–drug interaction is lacking. The aim of this study was to investigate the possible impact of two commonly used herbal medicines, garlic and cranberry, on the pharmacokinetics and pharmacodynamics of warfarin in healthy male subjects. Experimental approach: An open-label, three-treatment, randomized crossover clinical trial was undertaken and involved 12 healthy male subjects of known CYP2C9 and VKORC1 genotype. A single dose of 25mg warfarin was administered alone or after 2 weeks of pretreatment with either garlic or cranberry. Warfarin enantiomer concentrations, INR, platelet aggregation and clotting factor activity were measured to assess pharmacokinetic and pharmacodynamic interactions between warfarin and herbal medicines. Key results: Cranberry significantly increased the area under the INR–time curve by 30% when administered with warfarin compared with treatment with warfarin alone. Cranberry did not alter S- or R-warfarin pharmacokinetics or plasma protein binding. Co-administration of garlic did not significantly alter warfarin pharmacokinetics or pharmacodynamics. Both herbal medicines showed some evidence of VKORC1 (not CYP2C9) genotype-dependent interactions with warfarin, which is worthy of further investigation.Conclusions and implications: Cranberry alters the pharmacodynamics of warfarin with the potential to increase its effectssignificantly. Co-administration of warfarin and cranberry requires careful monitoring.

Effect of hypochlorhydria due to omeprazole treatment or atrophic gastritis on protein-bound vitamin B12 absorption.

Posted: 
November 13, 2010
Authors: 
Saltzman JR, Kemp JA, Golner BB, Pedrosa MC, Dallal GE, Russell RM
Journal: 
J Am Coll Nutr 13(6):584-91
Abstract: 

OBJECTIVE: To investigate the effects of hypochlorhydria and acidic drink ingestion on protein-bound vitamin B12 absorption in elderly subjects.

METHODS: Absorption of protein-bound vitamin B12 was examined in elderly normal subjects (n = 8), and in hypochlorhydric subjects due to omeprazole treatment (n = 8) or with atrophic gastritis (n = 3). Subjects underwent absorption tests of protein-bound vitamin B12 ingested with water, cranberry juice and 0.1 N hydrochloric acid.

RESULTS: Protein-bound vitamin B12 absorption was lower in the omeprazole-treated group (0.50%) compared to the normal group (1.21%; p

CONCLUSION: Omeprazole causes protein-bound vitamin B12 malabsorption, and ingestion of an acidic drink improves protein-bound vitamin B12 absorption.

Interaction between warfarin and cranberry juice

Posted: 
November 13, 2010
Authors: 
Aston JL, Lodolce AE, Shapiro NL
Journal: 
Pharmacotherapy 26(9):1314-9
Abstract: 

Warfarin is extensively used for anticoagulation to a target international normalized ratio of 2.0-3.0 for most indications or 2.5-3.5 for high-risk indications; however, many drugs and dietary supplements induce fluctuations in the international normalized ratio. Such fluctuations may lead to therapeutic failure or bleeding complications. Cranberry juice is increasingly used for the prevention and adjunctive treatment of urinary tract infections. The United Kingdom's Committee on Safety of Medicines has alerted clinicians to a potential interaction between warfarin and cranberry juice and has advised that patients avoid their concurrent use. Review and analysis of the literature revealed that ingestion of large volumes of cranberry juice destabilize warfarin therapy. Small amounts of juice are not expected to cause such an interaction. Clinicians should be aware of this potential interaction and monitor and counsel patients accordingly.

Pomelo juice, but not cranberry juice, affects the pharmacokinetics of cyclosporine in humans

Posted: 
November 11, 2010
Authors: 
Grenier J, Fradette C, Morelli G, Merritt GJ, Vranderick M, Ducharme MP
Journal: 
Clin Pharmacol Ther 79(3):255-62
Abstract: 

BACKGROUND: Cyclosporine (INN, ciclosporin) is a cytochrome P450 (CYP) 3A and P-glycoprotein (P-gp) substrate whose bioavailability increases when administered with grapefruit juice. It is unknown whether pomelo, a closely related citrus fruit, interacts with cyclosporine in humans. In addition, a case study reports that cranberry juice interacts with warfarin, a drug with a narrow therapeutic range. Cranberries have a high content of flavonoids, compounds with various metabolic effects, including interaction with P-gp in vitro. Although the effect of flavonoids is less evident in vivo, cranberry juice has become a very popular beverage, and it was deemed important to investigate whether it has an effect on the disposition of cyclosporine, another drug with a narrow therapeutic range.

METHODS: In an open-label, randomized, 3-way crossover study with a 14-day washout period between each dose, 12 healthy male volunteers received single oral 200-mg doses of cyclosporine according to the following regimens: 200 mg cyclosporine administered with 240 mL of pomelo juice, cranberry juice, or water under fasting conditions. Multiple whole blood samples were collected up to 36 hours after each dose. Concentrations were determined via a liquid chromatography-tandem mass spectrometry method.

RESULTS: Administration of pomelo juice with cyclosporine increased the area under the curve from time 0 to the last measurable concentration (AUCt), area under the curve from time 0 to infinity (AUCinf), and maximum blood concentration (Cmax) of cyclosporine with ratios of least squares means of 119.4% (95% confidence interval [CI], 113.4%-125.8%), 118.9% (95% CI, 113.8%-124.3%), and 112.1% (95% CI, 102.3%-122.8%), respectively. All 3 variables exhibited statistically significant increases (with Bonferroni adjustment), with P = .0001 for AUCt and AUCinf and P = .0167 for Cmax; however, only the increase in AUCt was judged to be clinically significant with a 95% CI outside the 80% to 125% boundaries. Cranberry juice had no clinically significant effect on the overall disposition of cyclosporine. After administration of cyclosporine with cranberry juice, the ratios of least squares means for AUCt, AUCinf, and Cmax for cyclosporine were 95.0% (95% CI, 90.3%-100.1%), 93.4% (95% CI, 89.2%-97.8%), and 95.2% (95% CI, 86.9%-104.2%), respectively.

CONCLUSION: These results suggest that pomelo juice increases the bioavailability of cyclosporine, possibly by inhibiting CYP3A or P-gp activity (or both) in the gut wall. However, drinking a glass of cranberry juice does not appear to significantly influence the disposition of cyclosporine.

Efficacy of cranberry juice on Helicobacter pylori infection: a double-blind, randomized placebo-controlled trial

Posted: 
November 10, 2010
Authors: 
Zhang L, Ma J, Pan K, Go VL, Chen J, You WC
Journal: 
Helicobacter 10(2):139-45
Abstract: 

BACKGROUND: Helicobacter pylori infection is a major cause of peptic ulcer disease and gastric cancer. This study postulated that cranberry juice would be effective in the suppression of H. pylori in an endemically infected population at high risk for gastric cancer.MATERIALS AND METHODS: A prospective, randomized, double-blind, placebo-controlled trial was conducted in Linqu County of Shandong Province, China, where 189 adults aged 48.9 +/- 11.2 years (mean +/- SD) with H. pylori infection were randomly divided into two groups: cranberry juice (n = 97) and placebo (n = 92). Participants were assigned to orally receive two 250-ml juice boxes of cranberry juice or matching placebo beverage daily for 90 days. The degree of H. pylori infection was determined using the 13C-urea breath test before randomization at 35 and 90 days of intervention to assess the efficacy of cranberry juice in alleviating infection.RESULTS: A total of 189 subjects with positive 13C-urea breath test results prior to randomization completed the study. At day 35 of intervention, 14 of the 97 (14.43%) from the the cranberry juice treatment group and 5 of the 92 (5.44%) of the placebo recipients had negative 13C-urea breath test results. After 90 days, the study concluded that 14 of the 97 subjects in the cranberry juice treatment group versus 5 of the 92 in the placebo group yielded negative test results. Eleven individuals from the cranberry juice treatment group and only two from the placebo group were negative at 35 and 90 days of experiment. These results are significant (p

Cranberry does not affect prothrombin time in male subjects on warfarin.

Posted: 
November 9, 2010
Authors: 
Li Z, Seeram NP, Carpenter CL, Thames G, Minutti C, Bowerman S.
Journal: 
J Am Diet Assoc 106(12):2057-61
Abstract: 

There have been case reports suggesting that cranberry beverages may interact with warfarin. To date, no research study has been conducted to examine the potential interaction of cranberry and warfarin. The current study is a randomized, placebo-controlled, double-blind, crossover study to investigate the effect of cranberry juice on prothrombin time as assessed by the international normalized ratio (INR). Seven subjects with atrial fibrillation on a stable dose of warfarin for 3 months were randomized to consume 250 mL of cranberry juice for 7 days, then placebo for 7 days, or vice versa. The washout period was 7 days. The prothrombin time/INR was measured at baseline, and on days 2, 4, 7, 10, 14, 16, 18, 21, and 24. Data were analyzed by the Student t test for paired values. The baseline INR was 2.28+/-0.54 for the cranberry group and 2.13+/-0.50 for the placebo group. For all test points, the INR did not change significantly from baseline. At day 7 on cranberry juice, the INR was 2.23+/-0.53 for cranberry first group and 2.16+/-0.40 for placebo first group. The mean differences between the cranberry and placebo groups were not statistically significant. Our results suggest no significant interaction between the daily consumption of 250 mL cranberry juice and warfarin. When counseling patients on dietary changes necessary during warfarin treatment, it does not seem necessary to eliminate daily cranberry juice consumption at amounts of 250 mL, but the INR should be followed up closely.

Effects of daily ingestion of cranberry juice on the pharmacokinetics of warfarin, tizanidine, and midazolam--probes of CYP2C9, CYP1A2, and CYP3A4

Posted: 
November 9, 2010
Authors: 
Lilja JJ, Backman JT, Neuvonen PJ
Journal: 
Clin Pharmacol Ther 81(6):833-9
Abstract: 

Case reports suggest that cranberry juice can increase the anticoagulant effect of warfarin. We investigated the effects of cranberry juice on R-S-warfarin, tizanidine, and midazolam; probes of CYP2C9, CYP1A2, and CYP3A4. Ten healthy volunteers took 200 ml cranberry juice or water t.i.d. for 10 days. On day 5, they ingested 10 mg racemic R-S-warfarin, 1 mg tizanidine, and 0.5 mg midazolam, with juice or water, followed by monitoring of drug concentrations and thromboplastin time. Cranberry juice did not increase the peak plasma concentration or area under concentration-time curve (AUC) of the probe drugs or their metabolites, but slightly decreased (7%; P=0.051) the AUC of S-warfarin. Cranberry juice did not change the anticoagulant effect of warfarin. Daily ingestion of cranberry juice does not inhibit the activities of CYP2C9, CYP1A2, or CYP3A4. A pharmacokinetic mechanism for the cranberry juice-warfarin interaction seems unlikely.

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