Antioxidants and chemotherapy: can they be used in combination?
Vitamins A, C and E, ubidecarenone (coenzyme Q10), garlic, ginkgo and green tea have antioxidant properties. Several review articles discuss the conflicting hypotheses on the potential benefits and potential adverse effects of using antioxidants for patients having chemotherapy; however, the evidence to support either argument is limited.
One hypothesis proposes that antioxidants interfere with the mechanism of action of chemotherapy drugs, thereby reducing their effect. The antitumour activity of many chemotherapy medicines relies on the actions of reactive oxidative species (ROS) — a type of free radical.
Excessive amounts of ROS lead to oxidative stress, which can severely damage DNA, proteins and lipids and lead to cell injury and cell death. Because antioxidants help to neutralise ROS, complementary and alternative medicines with antioxidant properties may protect cancer cells from the effects of cytotoxic therapy.
It is important to note that most chemotherapy medicines have several mechanisms of action, and the ability to generate free radicals depends on the dose and the localisation and metabolism of the anticancer medicine within specific tissues.
In contrast, other hypotheses argue that antioxidants help to reduce the toxicity and adverse effects of chemotherapy by protecting normal cells, and this has been shown in in vitro and in vivo studies. It has also been suggested that antioxidants increase the effectiveness of cytotoxic treatment and have direct cytotoxic effects at high doses.
Any effects, whether positive or negative, will depend on the type of antioxidant and the chemotherapy regimen being used. More research is required before recommendations can be made for specific antioxidants to be used as adjuncts to chemotherapy; therefore, it is best to discourage the use of complementary and alternative medicines that have strong antioxidant properties unless there is robust evidence to suggest otherwise.
More information on chemotherapy medicines that rely on ROS for antitumour activity can be found in the full UKMi document.
This FAQ is taken from a “Medicines Q&A” produced by UK Medicines Information. The full document, including references, is available from www.evidence.nhs.uk (prepared June 2013). NHS Evidence is provided by the National Institute for Health and Care Excellence and incorporates content formerly held in the National electronic Library for Medicines
Citation: Clinical Pharmacist DOI: 10.1211/CP.2013.11127257
Recommended from Pharmaceutical Press
Pharmacy Registration Assessment Questions 2 features more than 400 entirely new, closed book and calculation questions. It can be used in conjunction with the previous volume or on its own. All questions are in line with current GPhC guidance, enabling you to prepare for the pharmaceutical pre-registration exam with confidence.£35.00Buy now
Pharmacy Registration Assessment Questions 3 is the third volume in a series that follows on from the previous, highly popular Pharmacy Registration Assessment Questions 2. It features more than 400 entirely new, closed book and calculation questions. It can be used in conjunction with the previous volume or on its own.£35.00Buy now