Taking St. John’s wort (Hypericum perforatum) when taking atazanavir might result in reduced blood levels of the drug, which could lead to reduced effectiveness and eventual resistance. Individuals taking atazanavir should avoid taking St. John’s wort at the same time.

St. John's wort increases the activity of an enzyme in the body that metabolizes atorvastatin ²¹. Consequently, supplementation with St. John's wort may increase the metabolism of, and therefore reduce the activity of, atorvastatin.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Pharmacological research from Europe suggests that St. John’s wort (Hypericum perforatum) may reduce plasma levels of cyclosporine.²⁵ Two case reports also describe heart transplant patients taking cyclosporine who showed signs of acute transplant rejection after taking St. John’s wort extract.²⁶ In both cases, reduced plasma concentrations of cyclosporine were found. One report cites similar findings in three patients taking cyclosporine and St. John’s wort together.²⁷ Finally, similar drops in cyclosporine blood levels were reported in 45 kidney or liver transplant patients who began taking St. John’s wort.²⁸ Until more is known, people taking cyclosporine should avoid the use of St. John’s wort.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

One preliminary trial has suggested that St. John’s  wort(Hypericum perforatum) may reduce blood levels of digoxin.³⁴ In this study, healthy volunteers took digoxin for five days, after which they added 900 mg per day of St. John’s wort while continuing the daily digoxin. A normal blood level of digoxin was reached after five days of taking the drug, but this level dropped significantly when St. John’s wort was added. This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.^{35 , 36} Until more is known, people taking digoxin should avoid St. John’s wort.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Taking St. John’s wort (Hypericum perforatum) when taking fosamprenavir might result in reduced blood levels of the drug, which could lead to reduced effectiveness and eventual resistance. Individuals taking fosamprenavir should avoid taking St. John’s wort at the same time.

Studies have shown that taking indinavir together with St. John’s wort results in increased breakdown and dramatically reduced blood levels of indinavir.^{57 , 58} Therefore, people taking indinavir should not take St. John’s wort.

Indinavir is a protease inhibitor used to treat people with HIV infection. A pharmacological study gave indinavir to healthy volunteers for two days.⁵⁹ On day 3, volunteers added 900 mg of St. John’s wort extract per day. At the end of the study, it was found that St. John’s wort led to a significant reduction in serum levels of indinavir. Until more is known, people taking indinavir or other antiretroviral drugs for HIV infection should avoid using St. John’s wort.

St. John's wort increases the activity of an enzyme in the body that metabolizes lovastatin ⁶⁴. Consequently, supplementation with St. John's wort may increase the metabolism of, and therefore reduce the activity of, lovastatin.

In a study of healthy human volunteers, supplementing with St. John's wort greatly decreased omeprazole blood levels by accelerating the metabolism of the drug.⁷² Use of St. John's wort may, therefore, interfere with the actions of omeprazole.

In patients taking simvastatin, treatment with St. John's wort increased serum cholesterol levels, apparently because St. John's wort interfered with the effect of the medication.⁸¹

One case study of a 42-year old asthmatic woman reported that taking 300 mg per day of St. John’s wort extract led to a significant decrease in blood levels of theophylline.⁸² Following discontinuation of St. John’s wort, the patient’s blood levels of theophylline returned to an acceptable therapeutic level. This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.^{83 , 84} Until more is known, people taking theophylline should avoid St. John’s wort.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

According to a preliminary report, volunteers taking 900 mg per day of St. John’s wort were given a single dose of an anticoagulant similar in action to warfarin.⁸⁹ There was a significant drop in the amount of the drug measured in the blood. Seven case studies reported to the Medical Products Agency in Sweden also found a decrease in the anticoagulant activity of warfarin when St. John’s wort was taken at the same time.⁹⁰ This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.^{91 , 92} People taking warfarin should consult with their doctor before taking St. John’s wort.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

St. John's wort increases the activity of an enzyme in the body that metabolizes alprazolam¹⁴. Consequently, supplementation with St. John's wort may increase the metabolism of, and therefore reduce the activity of, alprazolam.

Preliminary research has suggested that St. John’s wort (Hypericum perforatum) may reduce blood levels of the tricyclic antidepressant amitriptyline.¹⁵ This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.^{16 , 17} Until more is known, people taking tricyclic antidepressants should avoid St. John’s wort.

Preliminary research has suggested that St. John’s wort (Hypericum perforatum) may reduce blood levels of the tricyclic antidepressant amitriptyline.¹⁸ This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.^{19 , 20} Until more is known, people taking tricyclic antidepressants should avoid St. John’s wort.

In a study of healthy volunteers, administration of St. John's wort (Hypericum perforatum) along with alprazolam decreased blood levels of alprazolam, compared with the levels when alprazolam was taken by itself.3 Individuals taking alprazolam should not take St. John's wort without supervision by a doctor.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Preliminary research has suggested that St. John’s wort (Hypericum perforatum) may reduce blood levels of the tricyclic antidepressant amitriptyline.²² This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.^{23 , 24} Until more is known, people taking tricyclic antidepressants should avoid St. John’s wort.

In a study of healthy volunteers, administration of St. John's wort (Hypericum perforatum) along with alprazolam decreased blood levels of alprazolam, compared with the levels when alprazolam was taken by itself.3 Individuals taking alprazolam should not take St. John's wort without supervision by a doctor.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Preliminary research has suggested that St. John’s wort (Hypericum perforatum) may reduce blood levels of the tricyclic antidepressant amitriptyline.²⁹ This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.^{30 , 31} Until more is known, people taking tricyclic antidepressants should avoid St. John’s wort.

Eight cases reported to the Medical Products Agency of Sweden suggest that St. John’s wort may interact with oral contraceptives and cause intramenstrual bleeding and/or changes in menstrual bleeding.³² One reviewer has suggested that St. John’s wort may reduce serum levels of estradiol.³³ It should be noted, however, that only three of the eight Swedish women returned to normal menstrual cycles after stopping St. John’s wort. Women taking oral contraceptives for birth control should consult with their doctor before taking St. John’s wort.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

In a study of healthy volunteers, administration of St. John's wort (Hypericum perforatum) along with alprazolam decreased blood levels of alprazolam, compared with the levels when alprazolam was taken by itself.3 Individuals taking alprazolam should not take St. John's wort without supervision by a doctor.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Preliminary research has suggested that St. John’s wort (Hypericum perforatum) may reduce blood levels of the tricyclic antidepressant amitriptyline.³⁷ This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.^{38 , 39} Until more is known, people taking tricyclic antidepressants should avoid St. John’s wort.

In a study of healthy volunteers, administration of St. John's wort (Hypericum perforatum) along with alprazolam decreased blood levels of alprazolam, compared with the levels when alprazolam was taken by itself.3 Individuals taking alprazolam should not take St. John's wort without supervision by a doctor.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Eight cases reported to the Medical Products Agency of Sweden suggest that St. John’s wort may interact with oral contraceptives and cause intramenstrual bleeding and/or changes in menstrual bleeding.⁴⁰ One reviewer has suggested that St. John’s wort may reduce serum levels of estradiol.⁴¹ It should be noted, however, that only three of the eight Swedish women returned to normal menstrual cycles after stopping St. John’s wort. Women taking oral contraceptives for birth control should consult with their doctor before taking St. John’s wort.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Eight cases reported to the Medical Products Agency of Sweden suggest that St. John’s wort may interact with oral contraceptives and cause intramenstrual bleeding and/or changes in menstrual bleeding.⁴² One reviewer has suggested that St. John’s wort may reduce serum levels of estradiol.⁴³ It should be noted, however, that only three of the eight Swedish women returned to normal menstrual cycles after stopping St. John’s wort. Women taking oral contraceptives for birth control should consult with their doctor before taking St. John’s wort.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Eight cases reported to the Medical Products Agency of Sweden suggest that St. John’s wort may interact with oral contraceptives and cause intramenstrual bleeding and/or changes in menstrual bleeding.⁴⁴ One reviewer has suggested that St. John’s wort may reduce serum levels of estradiol.⁴⁵ It should be noted, however, that only three of the eight Swedish women returned to normal menstrual cycles after stopping St. John’s wort. Women taking oral contraceptives for birth control should consult with their doctor before taking St. John’s wort.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Eight cases reported to the Medical Products Agency of Sweden suggest that St. John’s wort may interact with oral contraceptives and cause intramenstrual bleeding and/or changes in menstrual bleeding.⁴⁶ One reviewer has suggested that St. John’s wort may reduce serum levels of estradiol.⁴⁷ It should be noted, however, that only three of the eight Swedish women returned to normal menstrual cycles after stopping St. John’s wort. Women taking oral contraceptives for birth control should consult with their doctor before taking St. John’s wort.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

There have been no published reports about negative consequences of combining St. John’s wort (Hypericum perforatum)  (Hypericum perforatum)  (Hypericum perforatum) and fluoxetine. One case has been reported of an interaction between St. John’s wort and a weak serotonin reuptake inhibitor drug known as trazodone that is vaguely similar to fluoxetine.⁴⁸ In another case, a patient experienced grogginess, lethargy, nausea, weakness, and fatigue after taking one dose of paroxetine (Paxil®, another SSRI drug) after ten days of St. John’s wort use.⁴⁹ Nevertheless, some doctors are concerned about the possibility of an interaction between St. John’s wort and fluoxetine causing side effects (e.g., mental confusion, muscle twitching, sweating, flushing) known collectively as serotonin syndrome.^{50 , 51} Until more is known about interactions and adverse actions, people taking any SSRI drugs, including fluoxetine, should avoid St. John’s wort, unless they are being closely monitored by a doctor.

One report describes a case of serotonin syndrome in a patient who took St. John’s wort and trazodone, a weak SSRI drug.⁵² The patient experienced mental confusion, muscle twitching, sweating, flushing, and ataxia. In another case, a patient experienced grogginess, lethargy, nausea, weakness, and fatigue after taking one dose of paroxetine (Paxil®, an SSRI drug related to fluvoxamine) after ten days of St. John’s wort.⁵³ Until more is known about interactions and adverse actions, people taking any SSRI drugs, including fluvoxamine, should avoid St. John’s wort, unless they are being closely monitored by a doctor.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Preliminary research has suggested that St. John’s wort (Hypericum perforatum) may reduce blood levels of the tricyclic antidepressant amitriptyline.⁵⁴ This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.^{55 , 56} Until more is known, people taking tricyclic antidepressants should avoid St. John’s wort.

Eight cases reported to the Medical Products Agency of Sweden suggest that St. John’s wort may interact with oral contraceptives and cause intramenstrual bleeding and/or changes in menstrual bleeding.⁶⁰ One reviewer has suggested that St. John’s wort may reduce serum levels of estradiol.⁶¹ It should be noted, however, that only three of the eight Swedish women returned to normal menstrual cycles after stopping St. John’s wort. Women taking oral contraceptives for birth control should consult with their doctor before taking St. John’s wort.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Eight cases reported to the Medical Products Agency of Sweden suggest that St. John’s wort may interact with oral contraceptives and cause intramenstrual bleeding and/or changes in menstrual bleeding.⁶² One reviewer has suggested that St. John’s wort may reduce serum levels of estradiol.⁶³ It should be noted, however, that only three of the eight Swedish women returned to normal menstrual cycles after stopping St. John’s wort. Women taking oral contraceptives for birth control should consult with their doctor before taking St. John’s wort.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

In a study of healthy volunteers, administration of St. John's wort (Hypericum perforatum) along with alprazolam decreased blood levels of alprazolam, compared with the levels when alprazolam was taken by itself.3 Individuals taking alprazolam should not take St. John's wort without supervision by a doctor.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Cases reported to the Medical Products Agency of Sweden suggest that St. John’s wort may interact with oral contraceptives and cause intramenstrual bleeding and/or changes in menstrual bleeding.⁶⁵ One reviewer has suggested that St. John’s wort may reduce serum levels of estradiol.⁶⁶ It should be noted, however, that only three of the eight Swedish women returned to normal menstrual cycles after stopping St. John’s wort. Women taking oral contraceptives for birth control should consult with their doctor before taking St. John’s wort.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Although there have been no interactions reported in the medical literature, it is best to avoid using nefazodone with St. John’s wort unless you are under the supervision of a qualified healthcare professional.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Eight cases reported to the Medical Products Agency of Sweden suggest that St. John’s wort may interact with oral contraceptives and cause intramenstrual bleeding and/or changes in menstrual bleeding.⁶⁷ One reviewer has suggested that St. John’s wort may reduce serum levels of estradiol.⁶⁸ It should be noted, however, that only three of the eight Swedish women returned to normal menstrual cycles after stopping St. John’s wort. Women taking oral contraceptives for birth control should consult with their doctor before taking St. John’s wort.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Preliminary research has suggested that St. John’s wort (Hypericum perforatum) may reduce blood levels of the tricyclic antidepressant amitriptyline.⁶⁹ This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.^{70 , 71} Until more is known, people taking tricyclic antidepressants should avoid St. John’s wort.

One report described a case of serotonin syndrome in a patient who took St. John’s wort and trazodone, a weak SSRI drug.⁷³ The patient reportedly experienced mental confusion, muscle twitching, sweating, flushing, and ataxia. In another case, a patient experienced grogginess, lethargy, nausea, weakness, and fatigue after taking one dose of paroxetine after ten days of St. John’s wort use.⁷⁴

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Although St. John’s wort contains chemicals that bind MAO in test tubes, it is believed that the action of St. John’s wort is not due to MAOI activity.⁷⁵ However, because St. John’s wort may have serotonin reuptake inhibiting action (similar to the action of drugs such as Prozac®, it is best to avoid concomitant use of St. John’s wort with MAOI drugs.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Preliminary research has suggested that St. John’s wort (Hypericum perforatum) may reduce blood levels of the tricyclic antidepressant amitriptyline.⁷⁶ This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.^{77 , 78} Until more is known, people taking tricyclic antidepressants should avoid St. John’s wort.

One report described a case of serotonin syndrome in a patient who took St. John’s wort and trazodone, a weak SSRI drug.⁷⁹ The patient reportedly experienced mental confusion, muscle twitching, sweating, flushing, and ataxia. In another case, a patient experienced grogginess, lethargy, nausea, weakness, and fatigue after taking one dose of paroxetine (Paxil®, another SSRI drug) after ten days of St. John’s wort use.⁸⁰

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

In a study of healthy volunteers, administration of St. John's wort (Hypericum perforatum) along with alprazolam decreased blood levels of alprazolam, compared with the levels when alprazolam was taken by itself.3 Individuals taking alprazolam should not take St. John's wort without supervision by a doctor.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

One report described a case of serotonin syndrome in a patient who took St. John’s wort and trazodone.⁸⁵ The patient reportedly experienced mental confusion, muscle twitching, sweating, flushing, and ataxia. Until more is known, St. John’s wort should not be combined with trazodone except under expert clinical supervision.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Preliminary research has suggested that St. John’s wort (Hypericum perforatum) may reduce blood levels of the tricyclic antidepressant amitriptyline.⁸⁶ This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.^{87 , 88} Until more is known, people taking tricyclic antidepressants should avoid St. John’s wort.

Although there have been no interactions reported in the medical literature, it is best to avoid using venlafaxine with St. John’s wort unless you are under the supervision of a qualified healthcare professional.

The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

In a study of healthy volunteers, administration of 900 mg of St. John's wort one hour prior to fexofenadine resulted in a significant increase in blood levels of fexofenadine, compared with the blood levels after taking fexofenadine alone.⁹³ On the other hand, long-term administration of St. John's wort (300 mg three times per day for two weeks) did not alter blood levels of fexofenadine. Until more is known, St. John's wort should not be combined with fexofenadine, except under the supervision of a doctor.