What are the published side effects and contraindications for Horny Goat Weed, Tribulus terrestris, Tongkat Ali, ginseng, ashwagandha, yohimbe, and L‑arginine individually?
Executive summary
Published reports show each of the seven supplements can cause real, sometimes serious, adverse effects and carry specific contraindications: horny goat weed and yohimbe are flagged for cardiovascular and respiratory risks and product adulteration [1] [2] [3] [4], Tribulus has mostly gastrointestinal and rare renal/ hepatic signals and potential drug‑metabolism interactions [5] [6] [7], Tongkat Ali appears generally well tolerated short‑term but has reported GI, neurologic and rare hepatotoxic cases and possible interactions [8] [9] [10], ginseng commonly causes insomnia, GI and blood‑pressure/bleeding effects and is contraindicated in some cardiovascular and hormone‑sensitive conditions [11] [12] [13], ashwagandha is usually mild but carries liver and thyroid concerns plus immunomodulatory interactions [14] [15] [16], and L‑arginine mainly causes GI upset and can lower blood pressure and interact with nitrates, anticoagulants, and herpes virus susceptibility [17] [18] [19].
1. Horny Goat Weed — cardiac, respiratory, hormonal and adulteration risks
Clinical summaries and poison‑center reports list common mild effects (nausea, abdominal discomfort, dry mouth) and also document serious events including spasms, severe breathing problems, tachyarrhythmia, mood changes and hypotension; the herb may have estrogen‑like actions and alter hepatic drug metabolism, so it can interact with estrogens, blood‑pressure drugs, anticoagulants and drugs processed by the liver [20] [1] [21] [22], and regulators have flagged some horny‑goat‑weed products as adulterated with PDE‑5 drugs (tadalafil/sildenafil) which multiplies risk [2].
2. Tribulus terrestris — mostly GI and rare organ toxicity, plus metabolic interactions
Most sources describe gastrointestinal upset (stomach pain, diarrhea, nausea) and sleep/mood changes as the common adverse effects [5] [23] [24], while case reports and reviews raise alarms about potential kidney injury, acute tubular necrosis, and interactions via CYP3A4 and P‑glycoprotein that could amplify statin toxicity, clotting‑drug effects (clopidogrel), and other prescription medicines [6] [25] [7]; human trials are limited and manufacturers’ variability means contraindications are advised for pregnancy, breastfeeding and certain organ‑disease states [26] [7].
3. Tongkat Ali — short‑term tolerability but isolated serious hepatotoxicity and interaction concerns
Small clinical trials and safety reviews report infrequent GI upset, itching, headache and rash at conventional doses (100–600 mg/day) and emphasize limited long‑term human safety data [8] [9] [27], yet case reports describe Tongkat‑Ali–associated acute liver injury and isolated severe events when used in multi‑ingredient products, and pharmacologic interactions with blood‑glucose drugs, propranolol and immunosuppressants are noted in some references [10] [28] [29].
4. Ginseng — stimulant‑like effects, sleep disturbance, BP and coagulation interactions
Systematic reviews and clinical summaries list insomnia, nervousness, GI upset, headache and variable effects on blood pressure and heart rhythm as the common side effects [11] [12] [30]; ginseng can influence coagulation and warfarin metabolism, may worsen autoimmune disorders, and is often recommended to avoid in uncontrolled hypertension, certain cardiovascular conditions, pregnancy and during prolonged use beyond a few months [31] [32] [13].
5. Ashwagandha — generally mild but watch liver, thyroid and CNS‑depressant interactions
Randomized trials show ashwagandha is typically well tolerated for up to ~3 months with mild GI symptoms, drowsiness and headache, but multiple pharmacovigilance and LiverTox reports document rare cases of clinically apparent liver injury and reports of thyrotoxicosis and immunostimulation that can clash with immunosuppressants or thyroid hormone therapy; surgery and pregnancy are commonly advised as contraindications or to use only under medical supervision [14] [16] [15].
6. Yohimbe (yohimbine) — high‑risk cardiovascular and neuropsychiatric profile; many contraindications
Regulatory and clinical sources consistently characterize yohimbine as capable of producing hypertension, tachycardia, arrhythmia, anxiety, seizures and even hospitalization; product labeling is often inaccurate and supplements have produced severe adverse events, so yohimbe is contraindicated with many antidepressants, antihypertensives, stimulants, in pregnancy, and in people with mental‑health or cardiovascular disease [4] [3] [33] [34].
7. L‑arginine — GI and hemodynamic effects, interactions with nitrates and anticoagulants
Clinical guidance shows L‑arginine usually causes nausea, cramping, bloating and diarrhea, and can lower blood pressure—posing risks if combined with antihypertensives or nitrates—and may increase bleeding risk with anticoagulants or antiplatelet agents; rare but serious electrolyte and renal concerns appear with high‑dose or IV use, and herpes outbreaks can be precipitated in susceptible individuals [17] [18] [35] [19].