Background: Dimethyl sulfoxide (DMSO) has been used for medical treatment and as a pharmacological agent in humans since the 1960s. Today, DMSO is used mostly for cryopreservation of stem cells, treatment of interstitial cystitis, and as a penetrating vehicle for various drugs. Many adverse reactions have been described in relation to the use of DMSO, but to our knowledge, no overview of the existing literature has been made. Our aim was to conduct a systematic review describing the adverse reactions observed in humans in relation to the use of DMSO. Methods: This systematic review was reported according to the PRISMA-harms (Preferred Reporting Items for Systematic reviews and Meta-Analysis) guidelines. The primary outcome was any adverse reactions occurring in humans in relation to the use of DMSO. We included all original studies that reported adverse events due to the administration of DMSO, and that had a population of five or more. Results: We included a total of 109 studies. Gastrointestinal and skin reactions were the commonest reported adverse reactions to DMSO. Most reactions were transient without need for intervention. A relationship between the dose of DMSO given and the occurrence of adverse reactions was seen. Conclusions: DMSO may cause a variety of adverse reactions that are mostly transient and mild. The dose of DMSO plays an important role in the occurrence of adverse reactions. DMSO seems to be safe to use in small doses. Registration: PROSPERO CRD42018096117.

Background: Melatonin is traditionally administered orally but has a poor and variable bioavailability. This study aims to present an overview of studies investigating the pharmacokinetics of alternative administration routes of melatonin. Methods: A systematic literature search was performed and included experimental or clinical studies, investigating pharmacokinetics of alternative administration routes of melatonin in vivo. Alternative administration routes were defined as all administration routes except oral and intravenous. Results: 10 studies were included in the review. Intranasal administration exhibited a quick absorption rate and high bioavailability. Transdermal administration displayed a variable absorption rate and possible deposition of melatonin in the skin. Oral transmucosal administration of melatonin exhibited a high plasma concentration compared to oral administration. Subcutaneous injection of melatonin displayed a rapid absorption rate compared to oral administration. Conclusion: Intranasal administration of melatonin has a large potential, and more research in humans is warranted. Transdermal application of melatonin has a possible use in a local application, due to slow absorption and deposition in the skin. Oral transmucosal administration may potentially be a clinically relevant due to avoiding first-pass metabolism. Subcutaneous injection of melatonin did not document any advantages compared to other administration routes.

Background: Dimethyl sulfoxide (DMSO) has been used for medical treatment and as a pharmacological agent in humans since the 1960s. Today, DMSO is used mostly for cryopreservation of stem cells, treatment of interstitial cystitis, and as a penetrating vehicle for various drugs. Many adverse reactions have been described in relation to the use of DMSO, but to our knowledge, no overview of the existing literature has been made. Our aim was to conduct a systematic review describing the adverse reactions observed in humans in relation to the use of DMSO. Methods: This systematic review was reported according to the PRISMA-harms (Preferred Reporting Items for Systematic reviews and Meta-Analysis) guidelines. The primary outcome was any adverse reactions occurring in humans in relation to the use of DMSO. We included all original studies that reported adverse events due to the administration of DMSO, and that had a population of five or more. Results: We included a total of 109 studies. Gastrointestinal and skin reactions were the commonest reported adverse reactions to DMSO. Most reactions were transient without need for intervention. A relationship between the dose of DMSO given and the occurrence of adverse reactions was seen. Conclusions: DMSO may cause a variety of adverse reactions that are mostly transient and mild. The dose of DMSO plays an important role in the occurrence of adverse reactions. DMSO seems to be safe to use in small doses. Registration: PROSPERO CRD42018096117 .

Introduction: Radiation is widely used in the treatment of various cancers and in radiological imaging procedures. Ionizing radiation causes adverse effects, leading to decreased quality of life in patients, by releasing free radicals that cause oxidative stress and tissue damage. The sleep-hormone melatonin is a free radical scavenger, and induces several anti-oxidative enzymes. This review investigates the scientific literature on the protective effects of melatonin against exposure to ionizing radiation, and discusses the clinical potential of melatonin as prophylactic treatment against ionizing radiation damage. Methods: A systematic literature search was performed and included experimental or clinical studies written in English that investigated the protective effects of melatonin against gamma or X-ray irradiation in vivo. Studies were excluded if patients were treated with chemotherapy concomitantly. Results: 37 studies were included in the review. All were of experimental case-control design and employed animals. The studies demonstrated that exogenous melatonin reduced oxidative stress and inflammation in all investigated tissues. Furthermore, melatonin increased 30-day survival and protected against radiation enteritis. These protective effects were only documented when melatonin was administered prior to exposure to ionizing radiation. Discussion: This review documents that melatonin effectively protects animals against injury to healthy tissues from ionizing radiation. However, no studies have been performed in humans. If clinical studies can document similar protective effects, melatonin could have a great potential to prevent side effects of radiotherapy for cancer, to protect against increased long-term cancer risk in radiological imaging procedures, and to protect from radiation due to nuclear incidents.

Introduction: We aimed to investigate the pharmacokinetic properties and safety of melatonin administered by alternative routes of administration. Methods: This study employed a cross-over design in healthy female volunteers. Twenty-five milligrams of melatonin was administered intravenously, intravesically, rectally, transdermally, and vaginally. Blood samples were collected at specified time points up to 24 h following intravenous, intravesical, rectal, and vaginal administration, and up to 48 h following transdermal administration. Plasma melatonin concentrations were determined by radioimmunoassay. Sedation was evaluated by a simple reaction-time test, and sleepiness was assessed by the Karolinska Sleepiness Scale. Adverse events were registered for each route of administration. Results: Ten participants were included. We documented a mean (SD) time to maximal concentration of 51 (29) min for intravesical, 24 (20) min for rectal, 21 (8) h for transdermal, and 147 (56) min for vaginal administration. The mean (SD) elimination half-life was 47 (6) min for intravenous, 58 (7) min for intravesical, 60 (18) min for rectal, 14.6 (11.1) h for transdermal, and 129 (17) min for vaginal administration. The mean (SD) bioavailability was 3.6 (1.9)% for intravesical, 36.0 (28.6)% for rectal, 10.0 (5.7)% for transdermal, and 97.8 (31.7)% for vaginal administration. No significant changes in reaction times were observed following administration of melatonin by any of the administration routes. Increased tiredness was documented following transdermal administration only. No serious adverse effects were documented. Conclusion: Rectally and vaginally administered melatonin may serve as relevant alternatives to standard oral melatonin therapy. Transdermal delivery of melatonin displayed an extended absorption and can be applied if prolonged effects are intended. Intravesical administration displayed, as expected, a very limited bioavailability. Melatonin administered by these routes of administration was safe.