Willow bark
Willow bark/Drug Interactions:
AcetazolamideAcetazolamide: Based on pharmokinetic studies and two case reports of elderly patients who were chronically receiving aspirin, concomitant use of acetazolamide and salicylates may cause lethargy, incontinence, and confusion due to elevated unbound plasma acetazolamide concentrations and reduced plasma protein binding (30). However, the maximal binding capacity of serum for acetazolamide was not affected by salicylate. AlcoholAlcohol: Based on the findings of a meta-analysis, the combination of salicin and alcohol may increase the risk of gastrointestinal bleeding and gastritis (21). Anticoagulants and antiplateletsAnticoagulants and antiplatelets: Based on human study, Salicis cortex extract with 240mg salicin per day had significant inhibitory effects on platelet aggregation, but not to the extent of acetylsalicylate (28; 29). AntihyperlipidemicsAntihyperlipidemics: Based on a clinical study, willow bark extract may induce hypertriglyceridemia (17). AntihypertensivesAntihypertensives: Based on an adverse event in a clinical study, willow bark may cause blood pressure instability (11). Anti-inflammatory drugsAnti-inflammatory drugs: Based on laboratory studies, willow bark may have anti-inflammatory effects (41; 42; 43). Beta-blockersBeta-blockers: Theoretically, the concomitant use of beta-blockers with willow bark may impair the effectiveness of beta-blockers due to willow bark's proposed aspirin-like pharmacological actions.Carbonic anhydrase inhibitorsCarbonic anhydrase inhibitors: Based on in vitro study and two case reports, the concomitant use of carbonic anhydrase inhibitors with willow bark may increase the therapeutic and toxic effects of both the carbonic anhydrase inhibitor and the salicylate (30). DiureticsDiuretics: Theoretically, the concomitant use of diuretics with willow bark may reduce the effectiveness of diuretics and may enhance the risk for salicylic acid toxicity.HeparinHeparin: Based on human study, Salicis cortex extract with 240mg salicin per day had significant inhibitory effects on platelet aggregation, but not to the extent of acetylsalicylate (28; 29). MethotrexateMethotrexate: Theoretically, white willow may decrease the renal excretion of methotrexate resulting in toxic levels due to its salicin content.Non-steroidal anti-inflammatory drugs (NSAIDS)Non-steroidal anti-inflammatory drugs (NSAIDS): Theoretically, the concomitant use of NSAIDS with willow bark may increase the risk of stomach ulceration and bleeding due to the salicylate component of willow bark.Phenytoin (Dilantin?)Phenytoin (Dilantin?): Theoretically, the concomitant use of Dilantin? with willow bark's salicylates may increase the Dilantin? levels in the blood by plasma protein binding displacement, resulting in toxicity.ProbenecidProbenecid: Theoretically, the concomitant use of probenecid with willow bark may impair the effectiveness of probenecid due to willow bark's proposed aspirin-like pharmacological actions.Protein-bound drugsProtein-bound drugs: Due to the plasma protein-binding salicylate component of white willow bark, some other plasma protein-bound drugs may be displaced, possibly resulting in altered drug levels.SalicylatesSalicylates: Theoretically, the concomitant use of aspirin and willow bark may increase the risk of bleeding due to an additive pharmacological action.SpironolactoneSpironolactone: Theoretically, the concomitant use of spironolactone with willow bark may result in antagonistic or additive effects.SulfinpyrazoneSulfinpyrazone: Willow bark in combination with sulfinpyrazone may theoretically result in additive anti-platelet effects, which may increase bleeding time.SulfonylureasSulfonylureas: Theoretically, the concomitant use of sulfonylureas with willow bark may increase the effect of sulfonylureas, possibly increasing the side effects and toxicity.Valproic acidValproic acid: Theoretically, the concomitant use of valproic acid with willow bark may impair the effectiveness of valproic acid.Willow bark/Herb/Supplement Interactions:
AnticoagulantsAnticoagulants: Based on human study, Salicis cortex extract with 240mg salicin per day had significant inhibitory effects on platelet aggregation, but not to the extent of acetylsalicylate (28; 29). AntihyperlipidemicsAntihyperlipidemics: Based on a clinical study, willow bark extract may induce hypertriglyceridemia (17). AntihypertensivesAntihypertensives: Based on an adverse event in a clinical study, willow bark may cause blood pressure instability (11). Anti-inflammatory agentsAnti-inflammatory agents: Based on laboratory studies, willow bark may have anti-inflammatory effects (41; 42; 43). Black cohoshBlack cohosh: White willow may interact with guaiacum resin, black cohosh, sarsaparilla, and poplar bark to reduce chronic arthritic pain symptoms (16). CadmiumCadmium: Willow bark may have a high level of cadmium, which may increase concentrations of cadmium (32; 33; 34; 35). DiureticsDiuretics: Theoretically, the concomitant use of diuretic herbs or supplements with willow bark may reduce the effectiveness of the diuretic and may enhance the risk for salicylic acid toxicity.Guaiacum resinGuaiacum resin: White willow may interact with guaiacum resin, black cohosh, sarsaparilla, and poplar bark to reduce chronic arthritic pain symptoms (16). Poplar barkPoplar bark: White willow may interact with guaiacum resin, black cohosh, sarsaparilla, and poplar bark to reduce chronic arthritic pain symptoms (16). SalicylatesSalicylates: Theoretically, the concomitant use of salicylate herbs or supplements and willow bark may increase the risk of bleeding due to an additive pharmacological action.SarsaparillaSarsaparilla: White willow may interact with guaiacum resin, black cohosh, sarsaparilla, and poplar bark to reduce chronic arthritic pain symptoms (16). Tannin-containing herbs/supplementsTannin-containing herbs/supplements: The concomitant administration of tannin-containing herbs or supplements may result in a malabsorption of salicylic acid (23). Willow bark/Food Interactions:
Tannin-containing foodsTannin-containing foods: The concomitant administration of tannin-containing foods may result in a malabsorption of salicylic acid (23). Willow bark/Lab Interactions:
Leukemia testsLeukemia tests: Willow bark extract may decrease leukemia test results (22). Protein-bound drug levelsProtein-bound drug levels: Due to the plasma protein-binding salicylate component of white willow bark, some other plasma protein-bound drugs may be displaced, possibly resulting in altered drug levels (theoretical).Prothrombin timeProthrombin time: Willow bark may increase the prothrombin time due to its salicylate component (28; 29). TriglyceridesTriglycerides: Based on a clinical study, willow bark extract may induce hypertriglyceridemia (17).