K4 Elite
K4 Elite
Reduced glutathione (γ-glutamyl-cysteinyl-glycine) has been studied in humans by oral, inhaled and intravenous routes in randomised controlled trials: oral 250-1,000 mg/day for 6 months in healthy adults (Richie 2015) and 500 mg twice daily for 4 weeks (Allen & Bradley 2011, no change in biomarkers); inhaled 646 mg twice daily for 6 months in cystic fibrosis (Griese 2013, n=153, primary endpoint not met); intravenous 1,400 mg three times weekly for 4 weeks in Parkinson's disease (Hauser 2009, n=21); and intravenous 1,500 mg/m2 before oxaliplatin in colorectal cancer (Cascinu 2002, n=52). Trials generally report tolerability comparable to placebo. Separate safety signals relate to compounded intravenous products: in 2019 FDA reported seven patients with nausea, vomiting and, in one case, breathing difficulty requiring hospitalisation after IV glutathione compounded from a powder suspected of high endotoxin levels.
Each row records what a published study did: who it enrolled, the regimen it administered to those subjects, and what it reported. These are historical study descriptions, not protocols to follow.
| Study | Population | Regimen as reported | Primary findings |
|---|---|---|---|
| Richie et al., Eur J Nutr 2015 (randomised, double-blind, placebo-controlled; oral) Registry: NCT01044277
|
54 healthy non-smoking adults | Participants received oral glutathione 250 mg/day or 1,000 mg/day, or placebo, for 6 months followed by a 1-month washout. | At 6 months mean GSH levels rose 30-35% in erythrocytes, plasma and lymphocytes and 260% in buccal cells in the 1,000 mg group (P < 0.05), and 17% (blood) and 29% (erythrocytes) in the 250 mg group; levels returned to baseline after washout. |
| Allen & Bradley, J Altern Complement Med 2011 (randomised, double-blind, placebo-controlled; oral) | 40 adult volunteers without acute or chronic disease (39 completed per protocol) | Volunteers received oral glutathione 500 mg twice daily or placebo for 4 weeks. | No significant between-group change in urinary F2-isoprostanes or 8-OHdG, and no change in erythrocyte total, reduced or oxidised glutathione at week 4. |
| Griese et al., Am J Respir Crit Care Med 2013 (randomised, double-blind, placebo-controlled; inhaled) Registry: NCT00506688
|
153 patients with cystic fibrosis aged 8 years and older with FEV1 40-90% predicted (73 glutathione, 80 placebo) | Patients inhaled 646 mg glutathione sodium salt in 4 mL, or 0.9% saline, via an investigational eFlow nebuliser every 12 hours for 6 months. | FEV1 (pre-post difference P = 0.180; area under curve P = 0.205) did not differ between groups over 6 months; exacerbations and quality-of-life scores were not improved, and adverse-event incidence was similar between glutathione and placebo. |
| Visca et al., J Pediatr Gastroenterol Nutr 2015 (randomised, double-blind, placebo-controlled; oral) | 44 paediatric patients with cystic fibrosis aged 18 months to 10 years | Children received oral reduced glutathione or placebo (calcium citrate), each at 65 mg/kg/day divided into three doses with meals, for 6 months. | The glutathione group gained a mean 0.67 SD in weight-for-age z-score over 6 months versus placebo; the authors reported no adverse effects. |
| Hauser et al., Mov Disord 2009 (randomised, double-blind, placebo-controlled pilot; intravenous) | 21 patients with Parkinson's disease whose motor symptoms were not adequately controlled (11 glutathione, 10 placebo) | Patients received intravenous glutathione 1,400 mg or placebo three times a week for 4 weeks, with 8 weeks of post-treatment follow-up. | No significant difference in UPDRS change; glutathione was well tolerated, reported adverse events were similar between groups, and there were no withdrawals due to adverse events. |
| Cascinu et al., J Clin Oncol 2002 (randomised, double-blind, placebo-controlled; intravenous with oxaliplatin) | 52 patients with advanced colorectal cancer receiving bimonthly oxaliplatin-based chemotherapy | Patients received glutathione 1,500 mg/m2 as a 15-minute infusion before each oxaliplatin dose, or normal saline, with neurological and electrophysiological assessment after 4, 8 and 12 cycles. | Grade 2-4 neurotoxicity after 8 cycles occurred in 2 patients in the glutathione arm versus 11 in the placebo arm (P = .003), and after 12 cycles in 3 versus 8 (P = .004). |
Effects recorded in the cited reports. Frequencies are those the source reported, in the population that source studied.
| Effect | Frequency / context | Source |
|---|---|---|
| Adverse events comparable to placebo (inhaled route) | In the 6-month cystic fibrosis trial (n=153) the adverse-event incidence was similar between inhaled glutathione and placebo (Griese 2013); no percentages are given in the abstract. | Inhalation treatment with glutathione in patients with cystic fibrosis. A randomized clinical trial (Am J Respir Crit Care Med 2013) ↗ |
| Adverse events comparable to placebo (intravenous route, pharmaceutical-grade) | In the Parkinson's disease pilot (1,400 mg IV three times weekly for 4 weeks, n=21) reported adverse events were similar in the two groups and no safety concerns were identified (Hauser 2009). | Randomized, double-blind, pilot evaluation of intravenous glutathione in Parkinson's disease (Mov Disord 2009) ↗ |
| No adverse effects reported (oral route, paediatric) | Oral GSH 65 mg/kg/day for 6 months in 44 children with cystic fibrosis: authors report no adverse effects (Visca 2015). | Oral reduced L-glutathione improves growth in pediatric cystic fibrosis patients (J Pediatr Gastroenterol Nutr 2015) ↗ |
| Nausea, vomiting, difficulty breathing after compounded IV glutathione suspected of endotoxin contamination | FDA (1 February 2019) reported seven patients with adverse events 'ranging from nausea and vomiting to difficulty breathing, which required one patient to be hospitalized' immediately after glutathione 200 mg/mL intravenous injection compounded from a powder distributed by Letco Medical; FDA attributed the events to potentially high endotoxin levels and reminded compounders not to use dietary-supplement-grade glutathione for injectables. | FDA warns compounders not to use glutathione from Letco Medical to compound sterile drugs ↗ |
| Anaphylaxis and hepatotoxicity concerns with IV glutathione used for skin lightening (review-level) | A 2025 narrative review of glutathione for skin lightening states that intravenous glutathione 'is associated with serious safety concerns like anaphylaxis and hepatotoxicity, further aggravated by a lack of standardized dosing protocols'; frequencies are not quantified. | Exploring the Safety and Efficacy of Glutathione Supplementation for Skin Lightening: A Narrative Review (Cureus 2025) ↗ |
Interactions documented in trial reports, prescribing information or pharmacology references.
| Agent | Type | Note | Source |
|---|---|---|---|
| Cytotoxic chemotherapy and radiotherapy (general antioxidant caution) | pharmacodynamic (theoretical / review-level) | A JNCI review of randomised trials concluded that supplemental antioxidant use during chemotherapy and radiotherapy 'should be discouraged because of the possibility of tumor protection and reduced survival', while noting other data suggest normal tissues can be protected without loss of tumour control. | Should supplemental antioxidant administration be avoided during chemotherapy and radiation therapy? (J Natl Cancer Inst 2008) ↗ |
| Oxaliplatin (platinum chemotherapy) | pharmacodynamic (trial data) | Intravenous glutathione 1,500 mg/m2 given before oxaliplatin reduced grade 2-4 neurotoxicity in a 52-patient double-blind RCT; this was a deliberate co-administration under oncology supervision, and the trial was not powered to establish effects on tumour response or survival. | Neuroprotective effect of reduced glutathione on oxaliplatin-based chemotherapy in advanced colorectal cancer (J Clin Oncol 2002) ↗ |
Exclusions and label contraindications recorded in the cited sources.