Buchu

Buchu (Agathosma betulina) contains R-(+)-pulegone, a hepatotoxic monoterpene that is bioactivated by CYP2E1 and CYP1A2 to reactive metabolites (notably menthofuran) which deplete glutathione and cause centrilobular hepatocellular necrosis. A case report documented subfulminant liver failure attributed to buchu. Combined with other hepatotoxic drugs (especially acetaminophen, which also relies on glutathione for NAPQI detoxification), additive hepatotoxicity may result.

Avoid combination with hepatotoxic drugs. Limit buchu use to short-term, modest doses. Prefer A. betulina over A. crenulata (lower pulegone content). Monitor LFTs at baseline and every 4 weeks if used chronically. Discontinue immediately for jaundice, RUQ pain, or transaminase elevation. Avoid acetaminophen >2 g/day during buchu use.

Chronic alcohol use induces CYP2E1, which is the principal enzyme that bioactivates pulegone to hepatotoxic metabolites. In rat models, pretreatment with phenobarbital (CYP inducer) or diethylmaleate (glutathione depleter) potentiated pulegone hepatotoxicity, while pretreatment with 3-methylcholanthrene or piperonyl butoxide reduced it. Alcohol co-consumption can substantially increase buchu's hepatotoxic potential.

Counsel patients to abstain from alcohol entirely during buchu use. Avoid in patients with alcohol use disorder or known fatty liver disease.

Coumarins have been reported from Agathosma species and the related Rutaceae family. Buchu has been described in older monographs as exhibiting mild anticoagulant activity. Combined with warfarin or antiplatelet drugs, additive bleeding risk is theoretically possible, particularly if pulegone-induced hepatocyte injury impairs synthesis of clotting factors.

Monitor INR more frequently in patients on warfarin if buchu is initiated or stopped. Counsel patient on bleeding symptoms. Avoid use in patients with bleeding disorders.

Buchu has documented diuretic activity (listed in the German Commission E and historically in the US National Formulary). Diuretic-induced sodium depletion increases proximal tubular lithium reabsorption, raising serum lithium concentrations and the risk of lithium toxicity (tremor, ataxia, confusion, seizures).

Avoid combination if possible. If unavoidable, monitor serum lithium levels frequently (every 1-2 weeks initially), ensure adequate hydration and sodium intake. Watch for early signs of lithium toxicity. Adjust lithium dose downward if necessary.

Buchu has been used historically and is currently included in many over-the-counter herbal diuretic preparations. Combined with prescription diuretics, additive volume depletion and electrolyte disturbances (hypokalemia, hyponatremia, hypotension) may occur.

Monitor serum electrolytes (K+, Na+, creatinine) and blood pressure. Counsel patient on signs of dehydration (orthostatic dizziness, dry mucous membranes). Adjust diuretic regimen as needed.

Buchu has documented uterine-stimulant (emmenagogue and abortifacient) effects and can induce increased menstrual flow. Pulegone itself is associated with abortifacient activity. Combined with pharmacological uterotonics, additive uterine contraction may provoke premature labor or miscarriage.

Absolute contraindication in pregnancy. Avoid combination with labor-inducing agents. Counsel women of childbearing potential. Discontinue planning conception.