Safety and Pharmacokinetics of High-Dose Intravenous Vitamin C:
A Phase I Study in Advanced Cancer
An important question in research on high-dose intravenous vitamin C (intravenous ascorbic acid) is whether pharmacological concentrations can be achieved safely in humans, and how blood concentration, half-life, and tolerability change across different dose levels.
This Phase I study focused on patients with advanced solid tumours who had limited response to standard medical options, evaluating high-dose intravenous ascorbic acid as a single intervention with particular attention to safety, tolerability, and pharmacokinetics.
What Did the Study Do?
The study enrolled 15 patients with advanced solid tumours and divided them into five dose cohorts, with three patients in each cohort.
15
Five Dose Cohorts · Three Patients per Cohort
Patients received intravenous ascorbic acid on four consecutive days each week for a total of four weeks.
The study monitored adverse events, tolerability, peak blood concentrations, overall drug exposure, and clearance at the different dose levels.
Intravenous infusions were administered on four consecutive days each week.
The planned Phase I infusion course continued for four weeks.
A fixed infusion rate was used across all dose cohorts.
Which Intravenous Doses Were Tested?
Five escalating dose levels based on body surface area were used to examine how increasing doses affected plasma concentration, drug exposure, and tolerability.
30 g/m²
Dose 01
50 g/m²
70 g/m²
90 g/m²
110 g/m²
How Did Blood Ascorbate Concentrations Change?
Plasma ascorbate concentrations increased as the intravenous dose increased. The study provided human pharmacokinetic data on peak concentration, half-life, and the duration of sustained high plasma exposure.
10–20 mM
Higher Doses Created a Sustained Pharmacological Exposure Window
At doses of 70, 90, and 110 g/m², blood ascorbate concentrations remained at approximately 10–20 mM for around 5–6 hours, providing important human pharmacokinetic data for later clinical research.
The mean plasma half-life of intravenous ascorbic acid was approximately 2.0 ± 0.6 hours.
2.0 ± 0.6
Hours · Mean Half-Life
At a dose of 70 g/m², peak blood concentrations reached approximately 49 mM.
~49
mM · Peak Plasma Concentration
Doses of 70, 90, and 110 g/m² were able to maintain millimolar blood concentrations for several hours.
70+
g/m² · Doses Sustaining High Concentrations
Were Any Objective Tumour Responses Observed?
0
Objective Antitumour Responses
No Patient Demonstrated an Objective Antitumour Response
The study therefore supports the conclusion that high-dose intravenous ascorbic acid can achieve high pharmacological concentrations in humans with a degree of tolerability under study conditions. These pharmacokinetic findings should not be interpreted as evidence that intravenous vitamin C used alone can control advanced cancer.
Why Did the Study Ultimately Focus on Approximately 70–80 g/m²?
In addition to safety, the study compared how peak plasma concentrations and overall drug exposure changed as the dose was increased.
Above approximately 70 g/m², further increases in drug exposure began to plateau
The study found that when the dose was further increased from 70 g/m² to 90 or 110 g/m², peak plasma concentrations and overall drug exposure did not continue to increase proportionally. Based on the safety and pharmacokinetic data, the authors therefore suggested approximately 70–80 g/m² as a more appropriate dose range for further clinical research.
How Should This Study Be Interpreted?
This was a typical Phase I dose-exploration study. Its primary purpose was to evaluate safety, tolerability, and pharmacokinetics, rather than survival or tumour-control efficacy.
The tested doses were generally well tolerated, and a clear maximum tolerated dose was not identified during the study.
Overall Tolerability Was Favourable
Intravenous administration produced peak plasma concentrations in the tens of millimolar range and sustained high exposure for several hours.
Millimolar Concentrations Were Achievable
The study involved only 15 patients, had no randomised control group, and observed no objective tumour responses.
Anticancer Efficacy Was Not Established
Reaching Laboratory-Range Concentrations Does Not Establish Clinical Efficacy
An important contribution of this study was demonstrating that millimolar ascorbate concentrations can indeed be achieved in humans through intravenous administration. However, achieving a pharmacological concentration and producing an objective tumour response are two different research questions.
What Did This Study Contribute to Later Research?
01
Established Human Pharmacokinetic Data
The study provided data on peak concentration, half-life, exposure duration, and clearance, giving later studies a clearer human pharmacokinetic basis.
02
Confirmed Millimolar Concentrations Were Achievable
Peak plasma concentrations reached approximately 49 mM, while concentrations of 10–20 mM could be sustained for several hours.
03
Provided a Basis for Later Combination Studies
These dose and pharmacokinetic data allowed later research to move towards different cancer types and combination studies with standard cancer medicines.
One of the central questions in early research on high-dose intravenous vitamin C was whether humans could actually reach the millimolar ascorbate concentrations used in laboratory studies.
How Does BMS Clinic View This Evidence?
High-dose intravenous vitamin C differs substantially from routine oral vitamin supplementation. When doses are used to achieve pharmacological concentrations, the intervention should be approached with appropriate medical assessment and monitoring.
Before considering this type of medical support, relevant factors include the patient’s current disease status, existing cancer-care regimen, kidney function, G6PD status, electrolyte balance, and other individual risk factors.
BMS Clinic emphasises professional assessment based on current medical evidence and individual circumstances. Safety and pharmacokinetic data from Phase I studies help clarify the research basis of high-dose intravenous ascorbate, but should not be interpreted as established evidence of anticancer efficacy.
This page is provided for medical education and literature information purposes only. It is intended to help readers understand an early Phase I study evaluating the safety and pharmacokinetics of high-dose intravenous vitamin C in advanced cancer and does not replace diagnosis, assessment, or personalised medical advice from a qualified healthcare professional.
The study discussed was a small Phase I clinical trial primarily designed to evaluate the safety, tolerability, and pharmacokinetics of high-dose intravenous ascorbic acid. Although intravenous administration achieved high pharmacological concentrations, no objective antitumour responses were observed. The findings therefore do not demonstrate that high-dose vitamin C can control cancer, reduce tumour size, or prolong survival.
Patients with cancer considering high-dose intravenous vitamin C or other supportive medical approaches should first undergo appropriate assessment by a qualified healthcare professional based on their individual condition, current cancer treatment, kidney function, G6PD status, and other relevant risk factors.
Learn More About the Safety and Medical Assessment of High-Dose Intravenous Vitamin C
This Phase I study primarily provides information on the safety, tolerability and pharmacokinetics of high-dose intravenous vitamin C. It also showed that intravenous administration can achieve millimolar pharmacological concentrations, but no objective antitumour responses were observed. Anyone considering this type of medical support should first undergo professional assessment based on their disease status, current cancer care, kidney function, G6PD status and other individual risk factors.
References
Stephenson CM, Levin RD, Spector T, Lis CG. Phase I clinical trial to evaluate the safety, tolerability, and pharmacokinetics of high-dose intravenous ascorbic acid in patients with advanced cancer. Cancer Chemother Pharmacol. 2013;72(1):139–146.