Rhubarb root contains tannins that may possess inhibitory activity against angiotensin converting enzyme (ACE). Caution is advised in patients with high blood pressure or those taking ACE inhibitors or other blood pressure lowering agents.
If taken within one hour, antacids may decrease the effectiveness of rhubarb.
Overuse of rhubarb may cause potassium depletion, increasing the risk of the toxicity of other anti-arrhythmic agents (treat irregular heartbeat), such as quinidine. It may also increase the risk of digoxin toxicity.
Rhubarb and low doses of anti-psychotic drugs reduced the need for higher doses of anti-psychotic drugs in schizophrenic patients.
Although not well studied in humans, the combination of cisplatin and rhubarb may reduce the lethal toxicity and renal (kidney) toxicity of cisplatin, a common chemotherapeutic agent. The combination does not appear to interfere with the chemotherapeutic effect of cisplatin.
Rhubarb may increase potassium loss, thus aggravating electrolyte imbalance (e.g. with steroids). Concomitant use of rhubarb with other laxatives may increase electrolyte and fluid loss, potentiating their effect.
The high tannin level of rhubarb root may increase the chance of hepatic necrosis (liver death). Caution is advised when taking rhubarb with other potentially liver damaging agents due to the increased risk of liver damage.
Although not well studied in humans, the anthraquinones present in rhubarb may increase the risk of nephrotoxicity (kidney damage). Consult with a qualified healthcare professional, including a pharmacist, to check for interactions with other kidney damaging agents.
Rhubarb enhanced nifedipine's anti-pre-eclampsia effects.
Rhubarb's laxative effects with may reduce the absorption of other drugs taken by mouth due to a reduction in gastrointestinal transit time.
Rhubarb is frequently used as a small component in multi-herb traditional Chinese medicine decoctions. Examples of herbs that have been combined with rhubarb include: Alismatics orientalis, sanchi powder, and sage.
Because of rhubarb's potential to deplete potassium, concomitant use of rhubarb may increase cardiac toxicity of cardiac glycoside-containing herbs. An increase in potassium depletion and severe cardiac toxicity may be caused by concomitant use of rhubarb with cardio-active herbs, such as calamus, ginger, and Panax ginseng.
Rhubarb may enhance the effects of some herbs or supplements, such as the laxative effects of Glauber's salt. Rhubarb used with leech therapy reduced the need for anti-psychotic drugs in schizophrenic patients.
The high tannin level of rhubarb root may increase the chance of hepatic necrosis (liver cell death).
The action of jimsonweed may be increased in chronic use or abuse of rhubarb.
Concomitant use of rhubarb and licorice or horsetail may cause potassium depletion. Although not well studied in humans, rhubarb may also have diuretic properties, which may compound diuretic-induced potassium loss. Rhubarb is also proposed to cause bowel movements and may cause potassium depeletion when used with other laxatives. Rhubarb may increase potassium loss when used with steroids as well.
Although not well studied in humans, the anthroquinones present in rhubarb taken with other potentially nephrotoxic (kidney damaging) herbs may increase the risk for kidney damage.
Concomitant use of rhubarb with other herbs taken by mouth may reduce their absorption, due to reduction in gastrointestinal transit time. Rhubarb may also decrease mineral absorption. Its oxalate content may bind multivalent metal ions in the gastrointestinal tract and decrease their absorption.