HDI category: Significant hazard, dosage adjustment or close monitoring is needed |
Bonecal (Pharmanutra) | Levothyroxine | The efficacy of levothyroxine has been reduced by calcium carbonate. Calcium acetate and calcium citrate reduced levothyroxine absorption in pharmacokinetic studies |
Peppermint | Lansoprazole | Antacids may compromise the enteric coating of some commercially available peppermint oil capsules. H2-receptor antagonists and proton pump inhibitors may interact similarly |
St John’s wort | Amlodipine | St John’s wort significantly reduces the bioavailability of verapamil. Other calcium channel blockers would be expected to interact similarly |
HDI category: A potentially hazardous combination |
Glucosamine | Metformin | In a controlled study, glucosamine supplements with chondroitin had no effect on glycaemic control in patients taking oral antidiabetic drugs, but increases in blood glucose concentrations have occurred in patients with treated and untreated diabetes |
Omega 3 fish oil | Bisoprolol [2] | The hypotensive effect of propranolol might be enhanced by fish oils |
Ginkgo | Rabeprazole | Ginkgo modestly reduces omeprazole levels. Most other proton pump inhibitors are likely to be similarly affected |
HDI category: Doubt about outcome of concurrent usec |
Omega 3 fish oil | Aspirin [2] | The concurrent use of aspirin and fish oils caused at least additive effects on bleeding time in healthy subjects, but clinical studies in patients taking aspirin alone and with clopidogrel have found no evidence of an increase in incidence of bleeding episodes |
Cod liver oil | Aspirin [2] | The concurrent use of aspirin and fish oils caused at least additive effects on bleeding time in healthy subjects, but clinical studies in patients taking aspirin alone and with clopidogrel have found no evidence of an increase in incidence of bleeding episodes |
Cod liver oil | Bisoprolol Propranolol | The hypotensive effect of propranolol might be enhanced by fish oils |
Flaxseed | Rivaroxaban | Limited evidence suggests that flaxseed oil may have some antiplatelet effects, which could be additive with those of conventional antiplatelet drugs, and increase the risk of bleeding with anticoagulants |
Green tea | Lisinopril | Both black and green tea might cause a modest increase in blood pressure, which might be detrimental to the treatment of hypertension. Green tea reduced the effects of nadolol on blood pressure in healthy subjects |
Senna pods | Indapamide | Theoretically, patients taking potassium-depleting diuretics could experience excessive potassium loss if they also regularly use, or abuse, anthraquinone-containing substances such as senna |
Glucosamine | Co-codamol Paracetamol | Limited evidence suggests that glucosamine might reduce the efficacy of paracetamol (acetaminophen) |
Glucosamine | Furosemide Bendroflumethiazide [2] | Limited evidence from a large open study suggests that unnamed diuretics might slightly reduce the efficacy of glucosamine to some extent |
Echinacea | Midazolam | Echinacea does not appear to alter the AUC and clearance of oral midazolam, although the bioavailability may be increased. Clearance of intravenous midazolam may be modestly increased in patients taking Echinacea |
Hawthorn | Nifedipine | Limited evidence suggests that there may be additive blood pressure-lowering effects if hawthorn is taken with conventional antihypertensives, but the effects are small |
Visionace® (Vitabiotics) (lutein, carotenoids, myrtillus, flavonoid compounds) | Lansoprazole | The desired effect of betacarotene supplementation may be reduced in those taking proton pump inhibitors |
Evening primrose oil | Aspirin | Evening primrose oil can inhibit platelet aggregation and increase bleeding time. It has therefore been suggested that it may have additive effects with other antiplatelet drugs, but evidence of this is generally lacking |