Melatonin provides anxiolysis, enhances analgesia, decreases intraocular pressure, and promotes better operating conditions during cataract surgery under topical anesthesia

Does Melatonin Improve Sleep Following Primary Total Knee Arthroplasty? A Randomized, Double-Blind, Placebo-Controlled Trial

BACKGROUND

Sleep impairment following total knee arthroplasty (TKA) is common and may decrease patient satisfaction and recovery. Standardized postoperative recommendations for sleep disturbances have not been established. We aimed to assess whether melatonin use could promote healthy sleep and reduce sleep disturbance in the acute period following TKA.

METHODS

Patients undergoing primary, elective TKA between July 19, 2021 and January 4, 2024 were prospectively enrolled and randomized to receive either 5 mg of melatonin nightly or placebo for 14 days postoperatively. Participants recorded their nightly pain on the visual analog scale, the number of hours slept, and the number of night-time awakenings in a sleep diary starting the night of surgery (postoperative day [POD] 0). Sleep disturbance was assessed preoperatively and on POD 14 using the patient-reported outcome measurement information system sleep disturbance form. Epworth Sleepiness Scores were collected on POD 14 to assess sleep quality.

RESULTS

Of the 138 patients enrolled, 128 patients successfully completed the study protocol, with 64 patients in each group. Melatonin patients trended toward more hours of sleep on POD 2 (placebo: 5.0 ± 2.4, melatonin: 5.8 ± 2.0, P = .084), POD 3 (placebo: 5.6 ± 2.2, melatonin: 6.3 ± 2.0, P = .075), and averaged over POD 1 to 3 (placebo: 4.9 ± 2.0, melatonin: 5.6 ± 1.8, P = .073), although no differences were observed on POD 4 or after. Fewer night-time awakenings in the melatonin group were observed on POD 1 (placebo: 4.4 ± 3.9, melatonin: 3.6 ± 2.4, P = .197), although this was not statistically significant. Preoperative and postoperative Patient-Reported Outcomes Measurement Information System Sleep Disturbance score increases were comparable for both groups (placebo: 4.0 ± 8.4, melatonin: 4.6 ± 8.2, P = .894). The melatonin (65.4%) and placebo (65%) groups demonstrated similar rates of increased sleep disturbance.

CONCLUSIONS

Melatonin may promote longer sleep in the immediate postoperative period after TKA, although these benefits wane after POD 3. Disturbances in sleep should be expected for most patients, although melatonin may have an attenuating effect. Melatonin is safe and can be considered for TKA patients experiencing early sleep disturbances postoperatively.

Melatonin: Unveiling the functions and implications in ocular health

Melatonin, a versatile hormone produced by the pineal gland, has garnered considerable scientific interest due to its diverse functions. In the eye, melatonin regulates a variety of key processes like inhibiting angiogenesis by reducing vascular endothelial growth factor levels and protecting the blood-retinal barrier (BRB) integrity by enhancing tight junction proteins and pericyte coverage. Melatonin also maintains cell health by modulating autophagy via the Sirt1/mTOR pathways, reduces inflammation, promotes antioxidant enzyme activity, and regulates intraocular pressure fluctuations. Additionally, melatonin protects retinal ganglion cells by modulating aging and inflammatory pathways. Understanding melatonin's multifaceted functions in ocular health could expand the knowledge of ocular pathogenesis, and shed new light on therapeutic approaches in ocular diseases. In this review, we summarize the current evidence of ocular functions and therapeutic potential of melatonin and describe its roles in angiogenesis, BRB integrity maintenance, and modulation of various eye diseases, which leads to a conclusion that melatonin holds promising treatment potential for a wide range of ocular health conditions.

The Therapeutic Trip of Melatonin Eye Drops: From the Ocular Surface to the Retina

Melatonin is a ubiquitous molecule found in living organisms, ranging from bacteria to plants and mammals. It possesses various properties, partly due to its robust antioxidant nature and partly owed to its specific interaction with melatonin receptors present in almost all tissues. Melatonin regulates different physiological functions and contributes to the homeostasis of the entire organism. In the human eye, a small amount of melatonin is also present, produced by cells in the anterior segment and the posterior pole, including the retina. In the eye, melatonin may provide antioxidant protection along with regulating physiological functions of ocular tissues, including intraocular pressure (IOP). Therefore, it is conceivable that the exogenous topical administration of sufficiently high amounts of melatonin to the eye could be beneficial in several instances: for the treatment of eye pathologies like glaucoma, due to the IOP-lowering and neuroprotection effects of melatonin; for the prevention of other dysfunctions, such as dry eye and refractive defects (cataract and myopia) mainly due to its antioxidant properties; for diabetic retinopathy due to its metabolic influence and neuroprotective effects; for macular degeneration due to the antioxidant and neuroprotective properties; and for uveitis, mostly owing to anti-inflammatory and immunomodulatory properties. This paper reviews the scientific evidence supporting the use of melatonin in different ocular districts. Moreover, it provides data suggesting that the topical administration of melatonin as eye drops is a real possibility, utilizing nanotechnological formulations that could improve its solubility and permeation through the eye. This way, its distribution and concentration in different ocular tissues may support its pleiotropic therapeutic effects.

Secondary glaucoma: Toward interventions based on molecular underpinnings

Glaucoma is a heterogeneous group of progressive diseases that leads to irreversible blindness. Secondary glaucoma refers to glaucoma caused by a known underlying condition. Pseudoexfoliation and pigment dispersion syndromes are common causes of secondary glaucoma. Their respective deposits may obstruct the trabecular meshwork, leading to aqueous humor outflow resistance, ocular hypertension, and optic neuropathy. There are no disease-specific interventions available for either. Pseudoexfoliation syndrome is characterized by fibrillar deposits (pseudoexfoliative material) on anterior segment structures. Over a decade of multiomics analyses taken together with the current knowledge on pseudoexfoliative glaucoma warrant a re-think of mechanistic possibilities. We propose that the presence of nucleation centers (e.g., vitamin D binding protein), crosslinking enzymes (e.g., transglutaminase 2), aberrant extracellular matrix, flawed endocytosis, and abnormal aqueous-blood barrier contribute to the formation of proteolytically resistant pseudoexfoliative material. Pigment dispersion syndrome is characterized by abnormal iridolenticular contact that disrupts iris pigment epithelium and liberates melanin granules. Iris melanogenesis is aberrant in this condition. Cytotoxic melanogenesis intermediates leak out of melanosomes and cause iris melanocyte and pigment epithelium cell death. Targeting melanogenesis can likely decrease the risk of pigmentary glaucoma. Skin and melanoma research provides insights into potential therapeutics. We propose that specific prostanoid agonists and fenofibrates may reduce melanogenesis by inhibiting cholesterol internalization and de novo synthesis. Additionally, melatonin is a potent melanogenesis suppressor, antioxidant, and hypotensive agent, rendering it a valuable agent for pigmentary glaucoma. In pseudoexfoliative glaucoma, where environmental insults drive pseudoexfoliative material formation, melatonin's antioxidant and hypotensive properties may offer adjunct therapeutic benefits. This article is categorized under: Neurological Diseases > Molecular and Cellular Physiology.

Towards modifying the genetic predisposition for glaucoma: An overview of the contribution and interaction of genetic and environmental factors

Glaucoma, the leading cause of irreversible blindness worldwide, is a complex human disease, with both genetic and environmental determinants. The availability of large-scale, population-based cohorts and biobanks, combining genotyping and detailed phenotyping, has greatly accelerated research into the aetiology of glaucoma in recent years. Hypothesis-free genome-wide association studies have furthered our understanding of the complex genetic architecture underpinning the disease, while epidemiological studies have provided advances in the identification and characterisation of environmental risk factors. It is increasingly recognised that the combined effects of genetic and environmental factors may confer a disease risk that reflects a departure from the simple additive effect of the two. These gene-environment interactions have been implicated in a host of complex human diseases, including glaucoma, and have several important diagnostic and therapeutic implications for future clinical practice. Importantly, the ability to modify the risk associated with a particular genetic makeup promises to lead to personalised recommendations for glaucoma prevention, as well as novel treatment approaches in years to come. Here we provide an overview of genetic and environmental risk factors for glaucoma, as well as reviewing the evidence and discussing the implications of gene-environment interactions for the disease.

Experimental Data on the Role of Melatonin in the Pathogenesis of Nonalcoholic Fatty Liver Disease

Despite the increasing prevalence of nonalcoholic fatty liver disease (NAFLD) worldwide, its complex pathogenesis remains incompletely understood. The currently stated hypotheses cannot fully clarify the interrelationships between individual pathogenetic mechanisms of the disease. No appropriate health strategies have been developed for treating NAFLD. NAFLD is characterized by an accumulation of triglycerides in hepatic cells (steatosis), with the advanced form known as nonalcoholic steatohepatitis. In the latter, superimposed inflammation can lead to fibrosis. There are scientific data on NAFLD's association with components of metabolic syndrome. Hormonal factors are thought to play a role in the development of metabolic syndrome. Endogenous melatonin, an indoleamine hormone synthesized by the pineal gland mainly at night, is a powerful chronobiotic that probably regulates metabolic processes and has antioxidant, anti-inflammatory, and genomic effects. Extrapineal melatonin has been found in various tissues and organs, including the liver, pancreas, and gastrointestinal tract, where it likely maintains cellular homeostasis. Melatonin exerts its effects on NAFLD at the cellular, subcellular, and molecular levels, affecting numerous signaling pathways. In this review article, we discuss the experimental scientific data accumulated on the involvement of melatonin in the intimate processes of the pathogenesis of NAFLD.

The Effect of Melatonin on Analgesia, Anxiety, and Intraocular Pressure (IOP) in Cataract Surgery Under Topical Anesthesia

PURPOSE

This study investigated the effect of oral melatonin as a premedication before cataract surgery on pain score, anxiety, surgical conditions, and intraocular pressure (IOP) during cataract surgery with phacoemulsification under topical anesthesia.

DESIGN

This randomized, double-blind prospective study was conducted among 120 patients aged 50 to 80.

METHODS

Patients were randomly assigned to receive either sublingual melatonin 3 mg or placebo 60 min before surgery. Verbal anxiety and pain scores, heart rate, systolic and diastolic blood pressure, intraocular pressure, and quality of surgical conditions were recorded. The results were analyzed using SPSS 23 software, and statistical analysis consisted of χ² test and t-test, and a P value less than .05 was considered significant.

FINDINGS

There was a significant difference between the two groups regarding pain after the surgery before being discharged from the recovery room. The mean pain score in the melatonin group was lower than the placebo group in T4 (in the postoperative ward) (P < .05). The anxiety score of patients was lower in the melatonin group in T3 and T4 (during surgery and in the postoperative ward, respectively) (P < .05). IOP was significantly lower in the case group at the end of the surgery after receiving premedication (P = .021).

CONCLUSIONS

This study showed that 3 mg Sublingual melatonin premedication for patients undergoing cataract surgery under topical anesthesia reduced patients' anxiety scores, pain score, and IOP.

Regulation of Aqueous Humor Secretion by Melatonin in Porcine Ciliary Epithelium

Secretion of melatonin, a natural hormone whose receptors are present in the ciliary epithelium, displays diurnal variation in the aqueous humor (AH), potentially contributing to the regulation of intraocular pressure. This study aimed to determine the effects of melatonin on AH secretion in porcine ciliary epithelium. The addition of 100 µM melatonin to both sides of the epithelium significantly increased the short-circuit current (Isc) by ~40%. Stromal administration alone had no effect on the Isc, but aqueous application triggered a 40% increase in Isc, similar to that of bilateral application without additive effect. Pre-treatment with niflumic acid abolished melatonin-induced Isc stimulation. More importantly, melatonin stimulated the fluid secretion across the intact ciliary epithelium by ~80% and elicited a sustained increase (~50-60%) in gap junctional permeability between pigmented ciliary epithelial (PE) cells and non-pigmented ciliary epithelial (NPE) cells. The expression of MT3 receptor was found to be >10-fold higher than that of MT1 and MT2 in porcine ciliary epithelium. Aqueous pre-treatment with MT1/MT2 antagonist luzindole failed to inhibit the melatonin-induced Isc response, while MT3 antagonist prazosin pre-treatment abolished the Isc stimulation. We conclude that melatonin facilitates Cl- and fluid movement from PE to NPE cells, thereby stimulating AH secretion via NPE-cell MT3 receptors.

The Effect of Pre-emptive Oral Melatonin versus Placebo on Post-operative Analgesia in Infants after Thoracotomy for Closed Cardiac Surgeries: A Randomized Controlled Study

BACKGROUND: Thoracotomy pain is one of the severest types of pain that should be managed properly, especially in children. Opioids are the most widely prescribed analgesics for post-operative pain, but they can have a number of undesirable side effects. Melatonin could be employed as an adjuvant analgesic therapy during procedural discomfort as it had no known major side effects. STUDY DESIGN: This was a double-blinded, controlled randomized study. METHODS: Fifty patients divided randomly into two equal groups. One hour before surgery, children in M group (n = 25) were given 0.5 mg/kg orally of melatonin 3 mg tablets) and patients in Group P (n = 25) received a placebo (5 ml of water by syringe 5 ml) orally. Post-operative pethidine consumption over the 1st 24 h (mg) was recorded, the intraoperative fentanyl consumption (HR and ABP) at baseline, 1 min after induction, at skin incision, and every 30 min till the end of the surgery were recorded. Neonatal Infant Pain Score (NIPS) at 4 h, 6 h, 8 h, 12 h, 18 h, and 24 h postoperatively was recorded. Other reported data include demographic data, extubation time, days of ICU stay, and complications. RESULTS: Total post-operative pethidine consumption (mg) over 24 h was significantly lower in M group than P group (3.48 ± 2.23 vs. 7.68 ± 4.52 p = 0.01). Intraoperative fentanyl consumption (ug) was significantly lower in M group than P group (10.28 ± 4.98 vs. 17.08 ± 7.39 p < 0.001). As regards NIPS, it was statistically lower in M group than P group in all times except at 8 h and 24 h with significant difference. CONCLUSION: Oral melatonin is an effective and safe pre-emptive drug as it reduces the total post-operative pethidine consumption over the first 24 h and decreased post-operative pain scores without any unpleasant effects in pediatrics undergoing closed heart surgery.

Evaluation of the Effects of Exogenous Melatonin in Zygomatic Complex Fractures

Objective

The objective of this research was to evaluate the benefits of using exogenous melatonin in the preoperative period of patients with zygomatic complex fractures.

Materials and methods

A randomized, triple-blind clinical trial of independent samples was carried out. The sample was divided into two groups: G1 (melatonin) and G2 (placebo). Interventions were standardized with 10 mg melatonin or placebo the night before surgery and 1 h before the start of surgery. The studied variables were level of salivary cortisol, level of anxiety, pain, and use of rescue analgesics. Descriptive and inferential statistical analysis was performed, with a margin of error considered as 5%.

Results

A total of 14 patients were included, and after using the medication, the measurement of cortisol was reduced in the melatonin group (0.48 ± 0.25 to 0.43 ± 0.13 μg/100 ml) and increased in the placebo group (0.19 ± 0.12 to 0.23 ± 0.18 μg/100 ml). There was a reduction in the level of anxiety in the melatonin group and an increase in the placebo group. After two hours of surgery, the pain was statistically less in the melatonin group (4.50 ± 1.38) compared to the placebo group (6.17 ± 0.98). Six hours after surgery, pain showed regression in both groups. Patients in the placebo group (83.3%) used more rescue analgesics than melatonin group (33.3%) in the postoperative period.

Conclusions

Thus, this research demonstrated that melatonin can be effective in reducing salivary cortisol and anxiety after medication, and patients in the melatonin group needed less rescue analgesics in the postoperative period.

Can lubrication of the eyelid speculum reduce overall pain perception associated with cataract surgery by phacoemulsification performed under topical anesthesia?

Purpose

This study aimed to evaluate the effect of using the lubricated eyelid speculum on the overall pain perception by the subject patients who underwent cataract surgery by phacoemulsification technique under topical anesthesia.

Methods

A prospective interventional randomized comparative study was conducted at the tertiary eye care center, wherein adult patients scheduled for bilateral cataract surgery with phacoemulsification techniques under topical anesthesia were randomized to undergo surgery with two different modes of eyelid speculum insertion, either with or without lubrication of the eyelid speculum. Fifty percent of the patients underwent surgery with eyelid speculum without lubrication, and 50% with lubrication of the eyelid speculum. The primary outcome was to compare the level of overall pain perception among the subject patients of the two groups by using the Visual Analogue Scale (VAS) in the immediate postoperative period.

Results

The study included 130 patients who underwent bilateral cataract surgery (n = 260 eyes) under topical anesthesia, wherein n = 130 eyes underwent surgery using lubricated eyelid speculum and n = 130 eyes underwent surgery with dry eyelid speculum. Pain perception score assessed on the VAS (0-10 cm) ranged from 0.5 to 6, with a mean ± standard deviation of 2.06 ± 1.12. A significant correlation was found with two different methods of eyelid speculum insertion with reduced overall pain perception in patients with the use of lubricated eyelid speculum compared to the dry eyelid speculum (P = 0.0001).

Conclusion

The overall pain perception associated with cataract surgery performed by phacoemulsification technique under topical anesthesia can be further minimized by lubricating the eyelid speculum prior to insertion for exposing the globe.

Safety of higher doses of melatonin in adults: A systematic review and meta-analysis

Melatonin is commonly used for sleep and jetlag at low doses. However, there is less documentation on the safety of higher doses, which are being increasingly used for a wide variety of conditions, including more recently COVID-19 prevention and treatment. The aim of this review was to investigate the safety of higher doses of melatonin in adults. Medline, Scopus, Embase and PsycINFO databases from inception until December 2019 with convenience searches until October 2020. Randomised controlled trials investigating high-dose melatonin (≥10 mg) in human adults over 30 years of age were included. Two investigators independently abstracted articles using PRISMA guidelines. Risk of bias was assessed by a committee of three investigators. 79 studies were identified with a total of 3861 participants. Studies included a large range of medical conditions. The meta-analysis was pooled data using a random effects model. The outcomes examined were the number of adverse events (AEs), serious adverse events (SAEs) and withdrawals due to AEs. A total of 29 studies (37%) made no mention of the presence or absence of AEs. Overall, only four studies met the pre-specified low risk of bias criteria for meta-analysis. In that small subset, melatonin did not cause a detectable increase in SAEs (Rate Ratio = 0.88 [0.52, 1.50], p = .64) or withdrawals due to AEs (0.93 [0.24, 3.56], p = .92), but did appear to increase the risk of AEs such as drowsiness, headache and dizziness (1.40 [1.15, 1.69], p < .001). Overall, there has been limited AE reporting from high-dose melatonin studies. Based on this limited evidence, melatonin appears to have a good safety profile. Better safety reporting in future long-term trials is needed to confirm this as our confidence limits were very wide due to the paucity of suitable data.

Melatonin for pre-medication in children: a systematic review

Background

Melatonin’s effectiveness as an anxiolytic medication has been confirmed in adults; however, its efficacy in a paediatric population is unclear. A number of small studies have assessed its use in children as a pre-operative anxiolytic, with conflicting results.

Methods

We undertook a systematic review of pre-operative melatonin use in children. Four databases (MEDLINE, Embase, the Cochrane Central Register of Controlled Trials and Web of Science), and ‘ClinicalTrials.gov’ were searched for ongoing and completed clinical trials of relevance. Citation tracking reference lists and relevant articles were also accessed. The review was unrestricted by comparator or outcomes. Eleven studies were judged eligible for inclusion. There were high levels of heterogeneity in melatonin administration (in terms of dose and timing). Variable outcomes were reported and included: anxiety; anaesthetic success; analgesia; sedation; post-operative recovery; and safety. Outcomes were not always assessed with the same measures.

Results

Evidence to support melatonin’s anxiolytic properties in this setting is conflicting. Melatonin was associated with reduced sedative effects, post-operative excitement and improved emergence behaviour, compared to comparator drugs. One study reported the benefit of melatonin use on sleep disturbance at two weeks post-surgery. No adverse safety events were identified to be significantly associated with melatonin, affirming its excellent safety profile.

Conclusion

Despite potential advantages, including improved emergence behaviour, based on current evidence we cannot confirm whether melatonin is non-inferior to current “usual care” pre-medications. Further consideration of melatonin as an anxiolytic pre-medication in paediatric surgery is needed.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-022-03149-w.

The Roles of Transient Receptor Potential Ion Channels in Pathologies of Glaucoma

Transient receptor ion potential (TRP) channels are a cluster of non-selective cation channels present on cell membranes. They are important mediators of sensory signals to regulate cellular functions and signaling pathways. Alterations and dysfunction of these channels could disrupt physiological processes, thus leading to a broad array of disorders, such as cardiovascular, renal and nervous system diseases. These effects position them as potential targets for drug design and treatment. Because TRP channels can mediate processes such as mechanical conduction, osmotic pressure, and oxidative stress, they have been studied in the context of glaucoma. Glaucoma is an irreversible blinding eye disease caused by an intermittent or sustained increase in intraocular pressure (IOP), which results in the apoptosis of retinal ganglion cells (RGCs), optic nerve atrophy and eventually visual field defects. An increasing number of studies have documented that various TRP subfamilies are abundantly expressed in ocular structures, including the cornea, lens, ciliary body (CB), trabecular meshwork (TM) and retina. In alignment with these findings, there is also mounting evidence supporting the potential role of the TRP family in glaucoma progression. Therefore, it is of great interest and clinical significance to gain an increased understanding of these channels, which in turn could shed more light on the identification of new therapeutic targets for glaucoma. Moreover, this role is not understood completely to date, and whether the activation of TRP channels contributes to glaucoma, or instead aggravates progression, needs to be explored. In this manuscript, we aim to provide a comprehensive overview of recent research on TRP channels in glaucoma and to suggest novel targets for future therapeutic interventions in glaucoma.

The neuroprotective effect of melatonin in glutamate excitotoxicity of R28 cells and mouse retinal ganglion cells

Glaucoma is the leading cause of irreversible blindness. The progressive degeneration of retinal ganglion cells (RGCs) is the major characteristic of glaucoma. Even though the control of intraocular pressure could delay the loss of RGCs, current clinical treatments cannot protect them directly. The overactivation of N-methyl-D-aspartic acid (NMDA) receptors by excess glutamate (Glu) is among the important mechanisms of RGC death in glaucoma progression. Melatonin (MT) is an indole neuroendocrine hormone mainly secreted by the pineal gland. This study aimed to investigate the therapeutic effect of MT on glutamate excitotoxicity of mouse RGCs and R28 cells. The Glu-induced R28 cell excitotoxicity model and NMDA-induced retinal injury model were established. MT was applied to R28 cells and the vitreous cavity of mice by intravitreal injection. Cell counting kit-8 assay and propidium iodide/Hoechst were performed to evaluate cell viability. Reactive oxygen species and glutathione synthesis assays were used to detect the oxidative stress state of R28 cells. Retina immunofluorescence and hematoxylin and eosin staining were applied to assess RGC counts and retinal structure. Flash visual-evoked potential was performed to evaluate visual function in mice. RNA sequencing of the retina was performed to explore the underlying mechanisms of MT protection. Our results found that MT treatment could successfully protect R28 cells from Glu excitotoxicity and decrease reactive oxygen species. Also, MT rescued RGCs from NMDA-induced injury and protected visual function in mice. This study enriches the indications of MT in the treatment of glaucoma, providing practical research ideas for its comprehensive prevention and treatment.

Therapeutic Effects of Melatonin on Ocular Diseases: Knowledge Map and Perspective

Melatonin plays a critical role in the pathophysiological process including circadian rhythm, apoptosis, and oxidative stress. It can be synthesized in ocular tissues, and its receptors are also found in the eye, triggering more investigations concentrated on the role of melatonin in the eye. In the past decades, the protective and therapeutic potentials of melatonin for ocular diseases have been widely revealed in animal models. Herein, we construct a knowledge map of melatonin in treating ocular diseases through bibliometric analysis and review its current understanding and clinical evidence. The overall field could be divided into twelve topics through keywords co-occurrence analysis, in which the glaucoma, myopia, and retinal diseases were of greatest research interests according to the keywords burst detection. The existing clinical trials of melatonin in ocular diseases mainly focused on the glaucoma, and more research should be promoted, especially for various diseases and drug administration. We also discuss its bioavailability and further research topics including developing melatonin sensors for personalized medication, acting as stem cell therapy assistant drug, and consuming food-derived melatonin for facilitating its clinical transformation.

Role of melatonin in attenuation of hemodynamic response to intubation and anesthetic requirements: a randomized, controlled, double-blind study

BACKGROUND

Melatonin has been studied to have anxiolytic, sedative, and analgesic effects. However, there is limited data on the effect of melatonin in the attenuation of hemodynamic response to intubation. We aimed to study whether preanesthetic oral melatonin attenuates hemodynamic responses to intubation and anesthetic requirements.

METHODS

Sixty-four patients scheduled for laparoscopic cholecystectomy were randomized into melatonin or placebo group (n = 32 each). Melatonin group received two tablets (3 mg each) of melatonin, and the placebo group received two tablets of vitamin D3 120 min before induction. Hemodynamic parameters were recorded during induction and postintubation for 15 minutes. Total induction dose of propofol, total intraoperative fentanyl consumption, and adverse effects of melatonin were also noted.

RESULTS

Postintubation rise in heart rate (HR) was less in the melatonin group compared to the placebo group (10.59% vs. 37.08% at 1 min, respectively) (p < 0.0001). Maximum percentage increase in systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean blood pressure (MBP) was lesser in melatonin group than placebo group (SBP 9.25% vs. 37.73%, DBP 10.58% vs. 35.51%, MBP 9.99% vs. 36.45% at 1 min postintubation. respectively) (p < 0.0001). Induction dose of propofol (1.42 mg.kg^-1 vs. 2.01 mg.kg^-1) and the number of patients requiring additional fentanyl intraoperatively (3 vs. 11) were also significantly reduced in the melatonin group.

CONCLUSION

Premedication with 6 mg of oral melatonin resulted in significant attenuation of postintubation rise in HR, SBP, DBP, and MBP. It also reduced the induction dose of propofol, total intraoperative fentanyl consumption without any adverse effects.

Preoperative and Postoperative Endogenous Melatonin and Anxiety Levels and Their Correlation in Living Liver Donors

OBJECTIVES

High anxiety levels may lead to mental and physical changes that may affect quality of life. Melatonin has anxiolytic properties. It has been reported that administration of melatonin reduces anxiety. In this study, we examined the preoperative and postoperative anxiety levels of living liver donors and the correlation between anxiety levels and endogenous melatonin levels.

MATERIALS AND METHODS

This prospective clinical study included 56 living liver donors who underwent right hepatectomy (39 women, 17 men; average age of 29 ± 7 years). The anxiety levels were evaluated by using the Spielberger State-Trait Anxiety Inventory Test with a form for this test used to measure the current state of anxiety score and another form used to measure the underlying anxiety score of the patient. These forms were applied preoperatively and postoperatively. Blood samples were taken simultaneously for melatonin levels. Melatonin levels were measured using high-pressure liquid chromatography. Our primary outcomes were to determine the preoperative and postoperative endogenous melatonin and anxiety levels of living liver donors and to investigate their correlations.

RESULTS

A statistically significant difference was observed between preoperative and postoperative state of anxiety scores. The preoperative and postoperative underlying anxiety scores were similar. A statistically significant difference was found between the preoperative endogenous melatonin level and postoperative endogenous melatonin level. A significant correlation was not observed between the preoperative and postoperative current and underlying anxiety levels or endogenous melatonin levels.

CONCLUSIONS

Living liver donors had high anxiety levels during the preoperative and postoperative periods. A significant decrease was identified in the postoperative hour 24 endogenous melatonin level. These results may lay the foundation for interventions that can identify emotional changes as well as control and improve the mental health of living liver donors.

Fear and Anxiety Associated with Cataract Surgery Under Local Anesthesia in Adults: A Systematic Review

Cataract surgery is one of the most frequently performed surgical procedures worldwide. Patients usually experience strong negative emotions, such as fear and anxiety. A systematic review of the recent literature regarding the emotional states experienced during cataract surgery under local anaesthesia was performed based on the PubMed and Scopus databases. The objective of this review was to determine the causes and frequency of fear and anxiety, as well as methods for improving intraoperative experience and supporting the patient prior to surgery. Anxiety is mainly caused by fear of the surgery itself, fright of pain, and loss of vision. Abstaining and visual sensations experienced during cataract surgery also increased the preoperative anxiety. Women and hypochondriacs showed higher levels of anxiety. The greatest intensity of negative emotions occurred on the day of the cataract surgery. Patients operated on both eyes experienced greater fear and anxiety before the operation of the first eye surgery. In order to reduce patients’ negative experiences, pharmacological sedation, preoperative education and counselling, manual massage immediately before surgery, and listening to music during surgery are used. Taking this information into consideration allows the introduction of effective methods of eliminating the patient’s negative feelings in connection with cataract surgery, which leads to an improvement in the results of the operation and an increase in the patients’ sense of satisfaction and quality of life.

Melatonin mitigates disrupted circadian rhythms, lowers intraocular pressure, and improves retinal ganglion cells function in glaucoma

Glaucoma is a progressive optic neuropathy associated with damage to retinal ganglion cells (RGCs) and disrupted circadian rhythms. Melatonin is a promising substance to ameliorate glaucoma-associated compromised circadian rhythms, sleep, mood, and retinal cells function. However, studies estimating melatonin effects in glaucoma are currently lacking. Therefore, In this study, we investigated the effect of long-term (daily at 10:30 pm for 90 days) oral melatonin administration on systemic (Tb) and local to the organ of vision (IOP) circadian rhythms, pattern electroretinogram (PERG), sleep, and mood, depending on glaucoma stage in patients diagnosed with stable or advanced primary open-angle glaucoma. In a laboratory study in 15 of them, 24-hour records of salivary melatonin were obtained and MTNR1B receptor gene polymorphism was assessed. Melatonin increased the stability of the Tb circadian rhythm by improving its phase alignment and alignment with IOP. Melatonin time-dependently decreased IOP and IOP standard deviation (SD). IOP 24-hour mean and IOP SD decreases were more pronounced in individuals with the higher initial 24-hour IOP mean. Melatonin improved RGCs function in advanced glaucoma; N95 amplitude increase correlated positively with RGCs loss. The beneficial effects of melatonin on sleep and mood were greater in advanced glaucoma. Finally, delayed salivary melatonin and Tb phases were observed in MTNR1B G-allele carriers with advanced glaucoma. Combined, these results provide evidence for melatonin efficiency in restoring disrupted circadian rhythms in glaucoma with different effects of melatonin on systemic vs. local circadian rhythms, indicating that a personalized strategy of melatonin administration may further refine its treatment benefits.

Influence of Circadian Rhythm in the Eye: Significance of Melatonin in Glaucoma

Circadian rhythm and the molecules involved in it, such as melanopsin and melatonin, play an important role in the eye to regulate the homeostasis and even to treat some ocular conditions. As a result, many ocular pathologies like dry eye, corneal wound healing, cataracts, myopia, retinal diseases, and glaucoma are affected by this cycle. This review will summarize the current scientific literature about the influence of circadian patterns on the eye, focusing on its relationship with increased intraocular pressure (IOP) fluctuations and glaucoma. Regarding treatments, two ways should be studied: the first one, to analyze if some treatments could improve their effect on the ocular disease when their posology is established in function of circadian patterns, and the second one, to evaluate new drugs to treat eye pathologies related to the circadian rhythm, as it has been stated with melatonin or its analogs, that not only could be used as the main treatment but as coadjutant, improving the circadian pattern or its antioxidant and antiangiogenic properties.

Melatonin for preoperative and postoperative anxiety in adults

BACKGROUND

Anxiety in relation to surgery is a well-known problem. Melatonin offers an alternative treatment to benzodiazepines for ameliorating this condition in the preoperative and postoperative periods.

OBJECTIVES

To assess the effects of melatonin on preoperative and postoperative anxiety compared to placebo or benzodiazepines.

SEARCH METHODS

We searched the following databases on 10 July 2020: CENTRAL, MEDLINE, Embase, CINAHL, and Web of Science. For ongoing trials and protocols, we searched clinicaltrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform.

SELECTION CRITERIA

We included randomized, placebo-controlled or standard treatment-controlled (or both) studies that evaluated the effects of preoperatively administered melatonin on preoperative or postoperative anxiety. We included adult patients of both sexes (15 to 90 years of age) undergoing any kind of surgical procedure for which it was necessary to use general, regional, or topical anaesthesia.

DATA COLLECTION AND ANALYSIS

One review author conducted data extraction in duplicate. Data extracted included information about study design, country of origin, number of participants and demographic details, type of surgery, type of anaesthesia, intervention and dosing regimens, preoperative anxiety outcome measures, and postoperative anxiety outcome measures.

MAIN RESULTS

We included 27 randomized controlled trials (RCTs), involving 2319 participants, that assessed melatonin for treating preoperative anxiety, postoperative anxiety, or both. Twenty-four studies compared melatonin with placebo. Eleven studies compared melatonin to a benzodiazepine (seven studies with midazolam, three studies with alprazolam, and one study with oxazepam). Other comparators in a small number of studies were gabapentin, clonidine, and pregabalin. No studies were judged to be at low risk of bias for all domains. Most studies were judged to be at unclear risk of bias overall. Eight studies were judged to be at high risk of bias in one or more domain, and thus, to be at high risk of bias overall. Melatonin versus placebo Melatonin probably results in a reduction in preoperative anxiety measured by a visual analogue scale (VAS, 0 to 100 mm) compared to placebo (mean difference (MD) -11.69, 95% confidence interval (CI) -13.80 to -9.59; 18 studies, 1264 participants; moderate-certainty evidence), based on a meta-analysis of 18 studies. Melatonin may reduce immediate postoperative anxiety measured on a 0 to 100 mm VAS compared to placebo (MD -5.04, 95% CI -9.52 to -0.55; 7 studies, 524 participants; low-certainty evidence), and may reduce delayed postoperative anxiety measured six hours after surgery using the State-Trait Anxiety Inventory (STAI) (MD -5.31, 95% CI -8.78 to -1.84; 2 studies; 73 participants; low-certainty evidence). Melatonin versus benzodiazepines (midazolam and alprazolam) Melatonin probably results in little or no difference in preoperative anxiety measured on a 0 to 100 mm VAS (MD 0.78, 95% CI -2.02 to 3.58; 7 studies, 409 participants; moderate-certainty evidence) and there may be little or no difference in immediate postoperative anxiety (MD -2.12, 95% CI -4.61 to 0.36; 3 studies, 176 participants; low-certainty evidence). Adverse events Fourteen studies did not report on adverse events. Six studies specifically reported that no side effects were observed, and the remaining seven studies reported cases of nausea, sleepiness, dizziness, and headache; however, no serious adverse events were reported. Eleven studies measured psychomotor and cognitive function, or both, and in general, these studies found that benzodiazepines impaired psychomotor and cognitive function more than placebo and melatonin. Fourteen studies evaluated sedation and generally found that benzodiazepine caused the highest degree of sedation, but melatonin also showed sedative properties compared to placebo. Several studies did not report on adverse events; therefore, it is not possible to conclude with certainty, from the data on adverse effects collected in this review, that melatonin is better tolerated than benzodiazepines.

AUTHORS' CONCLUSIONS

When compared with placebo, melatonin given as premedication (as tablets or sublingually) probably reduces preoperative anxiety in adults (measured 50 to 120 minutes after administration), which is potentially clinically relevant. The effect of melatonin on postoperative anxiety compared to placebo (measured in the recovery room and six hours after surgery) was also evident but was much smaller, and the clinical relevance of this finding is uncertain. There was little or no difference in anxiety when melatonin was compared with benzodiazepines. Thus, melatonin may have a similar effect to benzodiazepines in reducing preoperative and postoperative anxiety in adults.

Natural Products: Evidence for Neuroprotection to Be Exploited in Glaucoma

Glaucoma, a leading cause of irreversible blindness worldwide, is an optic neuropathy characterized by the progressive death of retinal ganglion cells (RGCs). Elevated intraocular pressure (IOP) is recognized as the main risk factor. Despite effective IOP-lowering therapies, the disease progresses in a significant number of patients. Therefore, alternative IOP-independent strategies aiming at halting or delaying RGC degeneration is the current therapeutic challenge for glaucoma management. Here, we review the literature on the neuroprotective activities, and the underlying mechanisms, of natural compounds and dietary supplements in experimental and clinical glaucoma.

Effect of Melatonin on Postoperative Pain and Perioperative Opioid Use: A Meta-analysis and Trial Sequential Analysis

OBJECTIVES

We performed this meta-analysis in order to assess the effect of melatonin on postoperative pain and perioperative opioid consumption.

METHODS

We systematically searched PubMed, EMBASE, and the Cochrane Library until October 2019 for studies concerning the effect of melatonin vs. placebo on postoperative pain. We also searched for grey literature in ClnicalTrials.gov and grey literature databases, including OpenGrey and Grey Literature Report. We performed a meta-analysis of postoperative pain scores, perioperative opioid use, the number of patients with analgesic requirements, the time to the first analgesic requirement, length of hospital stay, and common reported adverse events of melatonin.

RESULTS

According to the inclusion and exclusion criteria, 15 studies with a total of 1,102 patients were included in the final analysis. Melatonin was significantly associated with decreased VAS score (24 hours postoperatively) compared to placebo (trial sequential analysis = conclusive; mean difference [MD] -0.86; 95% confidence interval [CI] -1.38, -0.34; P = 0.001). Patients randomly assigned to melatonin were administered less postoperative opioids than patients in the control groups (trial sequential analysis = inconclusive; MD -3.33 mg; 95% CI -5.28, -1.38; P = 0.0008). The need for analgesic requirements was significantly decreased in the melatonin group. Patients who received melatonin had a significantly longer time to the first analgesic requirement. Compared to the placebo group, there were no significant differences in terms of length of hospital stay, dizziness, headache, paresthesia, and nausea.

CONCLUSIONS

Given the low quality of evidence, minor degree of VAS score reduction, and inconclusive trial sequential analysis of postoperative opioid consumption, this meta-analysis neither supports nor opposes the effect of melatonin on postoperative pain.

The effect of melatonin on reduction in the need for sedative agents and duration of mechanical ventilation in traumatic intracranial hemorrhage patients: a randomized controlled trial

Purpose

This study aimed to determine the effect of exogenous melatonin on the number of sedative drugs and the duration of mechanical ventilation in traumatic intracranial hemorrhage patients in ICU.

Methods

This double-blind randomized clinical trial study was conducted in the ICU wards of Golestan Hospital, Ahvaz, Iran, from September 2017 to March 2018. In this study, 52 patients with intracerebral hemorrhage were selected by convenient sampling (26 patients in each group) and were randomly assigned to two groups of melatonin and control. Sedation and pain management package was applied to both groups. Outcomes: Amount of the sedative and opioid drug; mechanical ventilation time; ICU staying time; Glasgow Coma Score; hemodynamic parameters.

Results

There was no significant difference between them in terms of demographic characteristics. Cumulative doses of morphine and mechanical ventilation time were significant in two groups. (P < 0.05) The mean length of ICU staying was not significant. Glasgow Coma Score on the 6th day was significant in two groups (P < 0.05). Diastolic blood pressure was significant between groups (P < 0.001).

Conclusion

This study presented that morphine consumption and mechanical ventilation time were significantly lower in the melatonin group than in the control. Also, rise in GCS in the melatonin group was faster in the melatonin group than in the control. The use of melatonin can be recommended for patients with ICH in the ICU for better outcomes.

Melatonin: Implications for Ocular Disease and Therapeutic Potential

Melatonin, an indoleamine secreted mainly by the pineal gland, is known to modulate a wide range of circadian functions. However, this neurohormone is also synthesized within the eye and acts directly on ocular structures to mediate a variety of physiological processes. This review is focused on the role and therapeutic potential of melatonin in ocular diseases. We summarize data indicating that melatonin may represent a powerful tool to counteract ocular dysfunctions such as uveitis, glaucoma, age-related macular degeneration, and diabetic retinopathy. A search strategy was conducted to identify studies in PubMed (January 1990 to September 2017). In particular, we included experimental studies, clinical trials, and reviews to provide suitable insights and elucidations regarding the action of melatonin on age-related ocular disorders. Literature data suggest that melatonin could potentially protect ocular tissues by decreasing the production of free radicals and pro-inflammatory mediators. Additionally, melatonin appears to be safe and well-tolerated, even at high doses, and no adverse/side effects were reported. Although this topic remains under intense investigation, we can conclude that melatonin, as a single agent or in combination with other drugs, is an attractive pharmacological candidate for age-related ocular diseases.

Premedication effect of melatonin on propofol induction dose for anesthesia, anxiety, orientation and sedation after abdominal surgery: a double-blinded randomized trial

The present study addressed the effect of melatonin premedication on propofol induction dose for anesthesia in abdominal surgery. This is a double-blinded clinical trial in which abdominal surgery patients admitted to the Valiasr Hospital, Iran (n = 88) were enrolled and individually randomized into two groups: melatonin and placebo groups sublingually administered 3 mg of melatonin and placebo, respectively, 50 minutes before surgery. Their anxiety, orientation, and sedation were recorded before melatonin administration, anesthesia induction, and recovery, while we also recorded the propofol induction dose required for general anesthesia. Anxiety was seen less in the melatonin group than the placebo group (P < 0.05), whereas orientation was significantly different before anesthesia induction (P = 0.044) and sedation was the same before the induction (P = 0.044) and recovery (P = 0.049) in both groups, with a better efficiency in the melatonin group in which a lower dose of propofol was used (P = 0.002). The sedation, anxiety, and propofol dose used were lower in the melatonin group than the placebo group. The recommended dosage was 3 mg of melatonin once to achieve an anesthetic depth index or a bispectral index of 40. The study was approved by Ethical Committee of Arak University of Medical Sciences with IR.ARAKMU.REC.1395.432 code in July 2016, and the trial was registered in Iranian Registry of Clinical Trials with IRCT20141209020258N98 in September 2016.

Analgesic Efficacy of Melatonin: A Meta-Analysis of Randomized, Double-Blind, Placebo-Controlled Trials

Previous systematic reviews and meta-analyses of randomized controlled trials have reported controversial findings regarding the effects of melatonin on pain reduction. The aim of this study was to evaluate the efficacy of melatonin on pain among adults using a meta-analysis of randomized, double-blind, placebo-controlled trials (RDBPCTs). PubMed, EMBASE, the Cochrane Library, and the bibliographies of relevant articles were searched up to February 2020. Two of the authors independently evaluated eligibility of the studies based on the pre-determined criteria and extracted data. Standardized mean differences (SMDs) with 95% confidence intervals (CIs) for the pain score change were calculated using a random-effects meta-analysis. Out of 463 that met the initial criteria, a total of 30 trials, which involved 1967 participants with 983 in an intervention group and 984 in a control group, were included in the final analysis. In a random-effects meta-analysis, the use of melatonin reduced chronic pain in all the trials (5 studies, SMD -0.65, 95% CI -0.96 to -0.34, I² = 57.2%) and high-quality trials (4 studies, SMD -0.62, 95% CI -1.01 to -0.23, I² = 49.3%). Moreover, the use of melatonin significantly reduced acute postoperative pain (11 studies, SMD -0.82, 95% CI -1.40 to -0.25, I² = 93.0%). However, the subgroup meta-analysis of high-quality RDBPCTs showed no significant association between them (6 studies, SMD -0.21, 95 % CI -0.66 to 0.24, I² = 82.4%). The current study suggests that melatonin might be used in treatment of chronic pain, while there is no sufficient evidence for acute postoperative or procedural pain. Further trials are warranted to confirm its analgesic effect.

Safety and Efficacy of Oral Melatonin When Combined with Thoracic Epidural Analgesia in Patients with Bilateral Multiple Fracture Ribs

BACKGROUND

The purpose of this study is to evaluate the safety and efficacy of oral melatonin administered with thoracic epidural analgesia in patients with multiple bilateral fractured ribs.

PATIENTS AND METHODS

A prospective, double-blind randomized control study was carried out on 80 patients of either sex, American Society of Anesthesiologists (ASA) Grade I and II, aged above 18 years, presenting with multiple bilateral fractured ribs. They were randomly divided into two groups, 40 patients each. Placebo group patients received oral placebo tablets and melatonin group (TEA and melatonin) patients received oral melatonin tablets (5 mg), about 1 hour before epidural infusion of local anesthetics and then every 12 hours till the cessation of bupivacaine infusion.

RESULTS

Melatonin administration was associated with a significant decrease in total morphine analgesia consumption, from 31.8 ± 1.41 mg in the TE group to 13.03 ± 0.85 mg in the melatonin group (P < 0.001), with a significant decrease (P < 0.001) in the mean infusion rate of bupivacaine required for controlling the pain, from 0.17 ± 0.014 mL/kg/hour in the TE group to 0.12 ± 0.001 mL/kg/hour in the melatonin group. The duration of bupivacaine infusion in the melatonin group was also significantly shorter than in the TE group (96.48 ± 1.87 and 100.05 ± 3.39 hours, resp., P < 0.001).

CONCLUSION

We conclude that premedication of patients with 5 mg melatonin is associated with significant prolongation of thoracic epidural analgesic effects compared to placebo.

REGISTRATION

This clinical study was registered at Pan African Clinical Trial Registry with no. "PACTR 201711002741378" on 02-11-2017.

Understanding and Optimizing Tourniquet Use During Extremity Surgery

Tourniquet use during extremity surgery is commonplace and a relatively safe practice. The surgical team's knowledge of the patient history, proper assessment, and indications and contraindications for and risks of tourniquet use can prevent unwanted outcomes. Exploration of these critical areas reinforces perioperative nurses' awareness and understanding of safe tourniquet use. Additionally, a review of the physiological effect of tourniquets on the skin, the body's response to local compression, the risk of vascular compromise, and the effect of the tourniquet on postoperative pain and swelling provides insight into AORN recommended practice guidelines. This article summarizes the indications and assessments for and risks of tourniquet use for patients during extremity surgery. An understanding of these topics can improve surgical outcomes and promote safe perioperative care.

Hypotensive Effect of Nanomicellar Formulation of Melatonin and Agomelatine in a Rat Model: Significance for Glaucoma Therapy

BACKGROUND

Melatoninergic agents are known to reduce intraocular pressure (IOP). The present study was performed to evaluate the effect of nanomicellar formulations of melatoninergic agents on IOP in the rat.

METHODS

Tonometry was used to measure IOP in eyes instilled with melatonin or agomelatine. Ocular hypertension was induced by the injection of methylcellulose in the anterior chamber.

RESULTS

Melatonin formulated in nanomicelles had a longer lasting hypotonizing effect on IOP with respect to melatonin in saline. Nanomicellar formulations of melatonin and agomelatine, either alone or in combination, had lowering effects that did not depend on their concentration or their combination, which, however, resulted in an increased duration of the hypotonizing effect. The duration of the lowering effect was further increased by the addition of lipoic acid.

CONCLUSIONS

We demonstrated the effective hypotonizing activity of melatonin and agomelatine in combination with lipoic acid. Although results in animals cannot be directly translated to humans, the possibility of developing novel therapeutical approaches for patients suffering from hypertensive glaucoma should be considered.

Does wild rabbit population size affect connectivity?

<p>Wild rabbit is a relevant species in the Iberian Peninsula due to its ecological  and economic roles. Conservationists and game managers therefore have a shared interest in assuring the existence of resilient and sustainable populations. Although management principles and guidelines are  mostly known and understood, often the results are not as good as expected. Local abundance can vary significantly even in short periods, while the colonisation of adjacent territories is uncommon, probably due to the territorial behaviour of the species. Aware that the foundation of nuclei requires interaction among individuals, we hypothesised that rabbit abundance plays a significant part in population connectivity. In order to find out whether the population size affects nuclei connectivity, we conducted a graph theory-based connectivity analysis. The results confirm that connectivity grows with rabbit abundance, but only to a certain degree, and there is a spatial separation of the nuclei regardless of the population size. These outcomes suggest that a comprehensive wild rabbit population increment plan should address both the abundance and spatial distribution, but should not aim at achieving a continuous distribution of wild rabbit with constant or similar abundance. Regarding specific management actions, we argue that in restocking operations new nuclei should be located within dispersal range from the existing ones to promote inter-nuclei connectivity, but not too close, as the nuclei segregation tendency is likely to persist due to the species’ territoriality.</p>

Localization of melatonin and its receptors (melatonin 1a and 1b receptors) in the mouse inner ear

Background: In the inner ear, evidence has been gathered indicating that melatonin plays important roles in inner ear physiology and pathophysiology. However, no attempt has been made previously to investigate the localization or expression of melatonin and its receptors in the whole inner ear. Aims/objectives: To analyze the presence of melatonin and its receptors in the normal mouse inner ear. Material and methods: C57BL6/J mice were used in this study. The localizations of melatonin, MT1a and MT1b in the inner ear, i.e. cochlea, vestibular end organs, vestibular ganglion and endolymphatic sac (ES), were studied by immunohistochemistry. Results: The organ of Corti, spiral ganglion, vestibular ganglion, vestibular sensory cells, vestibular dark and transitional cells, and ES epithelial cells showed an immunofluorescence reaction to melatonin, MT1a and MT1b. Conclusion and significance: The present findings show that melatonin and its receptors (MT1a and MT1b) are present in the inner ear, thus supporting the hypothesis that melatonin plays a physiological role in the inner ear.

Effect of nutritional supplement based on melatonin on the intraocular pressure in normotensive subjects

PURPOSE

To evaluate the effect of a new nutritional supplement based on melatonin on the intraocular pressure (IOP) in normotensive subjects.

PATIENTS AND METHODS

A short-term prospective study was designed. Sixty-seven normotensive subjects were recruited. Patients were divided into two groups. The daily group (DG) (n = 18) was instructed to take the supplement between 22:00 and 23:00 (before sleeping) for 3 consecutive days. IOP was measured from 10.00 to 11.00 am the day before treatment and during the 3 days of experiment. The acute group (AG) (n = 49) was instructed to take the supplement after the second measure (11.00) of the second day. IOP was measured 1 h and just before the intake of the supplement and 1 and 2 h after. All measurements in this group were taken 1 day before without any supplement (control) and the day of experiment.

RESULTS

The DG group showed a significant decrease in IOP after supplement intake in all days of experiment, from 14.9 ± 3.4 mm Hg to 13.8 ± 2.9 mm Hg after 3 days of experiment (p value < 0.001). For AG, IOP did not change during the control day; however, a reduction of 1 mm Hg was found 2 and 3 h after supplement intake, from 15.7 ± 2.5 mm Hg to 14.7 ± 2.5 mm Hg and 15.1 ± 2.7 mm Hg, respectively, being statistically significant (p value < 0.001).

CONCLUSION

The supplement based on melatonin was able to reduce the IOP in normotensive subjects after 2 h of intake. Moreover, the daily intake showed a reduction in IOP during the 3 days of experiment.

Melatonin and the control of intraocular pressure

Melatonin is not only synthesized by the pineal gland but by several ocular structures. This natural indoleamine is of great importance for regulating several eye processes, among which pressure homeostasis is included. Glaucoma, the most prevalent eye disease, also known as the silent thief of vision, is a multifactorial pathology that is associated to age and, often, to intraocular hypertension (IOP). Indeed IOP is the only modifiable risk factor and as such medications are available to control it; however, novel medications are sought to minimize undesirable side effects. Melatonin and analogues decrease IOP in both normotensive and hypertensive eyes. Melatonin activates its cognate membrane receptors, MT₁ and MT₂, which are present in numerous ocular tissues, including the aqueous-humor-producing ciliary processes. Melatonin receptors belong to the superfamily of G-protein-coupled receptors and their activation would lead to different signalling pathways depending on the tissue. This review describes the molecular mechanisms underlying differential functionalities that are attributed to melatonin receptors. Accordingly, the current work highlights the important role of melatonin and its analogues in the healthy and in the glaucomatous eyes, with special attention to the control of intraocular pressure.

Effect of Melatonin and Its Analogs on Tear Secretion

Melatonin has been shown to enhance tear secretion associated with dinucleotide diadenosine tetraphosphate. This study investigated the isolated action of melatonin and its analogs, agomelatine, N-butanoyl-2-(2-methoxy-6H-isoindolo[2,1-a]indol-11-yl) ethanamine (IIK7), and 5-methoxycarbonylamino-N-cetyltryptamine (5-MCA-NAT) (10 µl at 100 µM), on tear secretion when applied topically in the rabbit cornea and its relationship with the melatonin MT1, MT2, and MT3/quinone reductase QR2 receptors. The results showed a significant increase in tear secretion, with a maximal effect at 60 minutes for the agonists (138.9% ± 6.5%, 128.9% ± 6.4%, and 120.0% ± 5.2%, respectively; P < 0.05; 100% control) but not for melatonin (101.6% ± 7.9%; P > 0.05). Agonist action was tested combined with the antagonists DH97 (MT2 selective), prazosin (MT3/QR2 inhibitor), and luzindole (nonselective MT membrane receptor) (10 µl at 100 µM). DH97 reversed the effect of agomelatine, IIK7, and 5-MCA-NAT up to 30.85% ± 7.6%,108% ± 7.2%, and 87.01% ± 7.6%, respectively (P < 0.05; 100% control). Luzindole antagonized agomelatine and 5-MCA-NAT up to 67.35% ± 7.6% and 92.12% ± 8%, respectively (P < 0.05). Prazosin only reversed 5-MCA-NAT action up to 84.2% ± 7.7% (P < 0.05). These results suggest different pathways for the agonists to act through MT membrane receptors. Therefore, agomelatine, IIK7, and 5-MCA-NAT act through MT membrane receptors as secretagogues of tear secretion, and these analogs could be considered excellent therapeutic candidates for dry eye treatment. SIGNIFICANCE STATEMENT: Currently, dry eye with aqueous deficit is treated by adding artificial tears palliatively. This study shows that topical installation of three melatonin analogs (agomelatine, IIK7, and 5-MCA-NAT), but not melatonin, in therapeutic doses in the rabbit cornea significantly increases tear production, acting through different melatonin membrane receptor subtypes. Therefore, this study suggests that melatoninergic compounds could be considered excellent therapeutic candidates for dry eye treatment and ocular surface diseases occurring with a reduction in tear production.

Effect of orally administered melatonin on intraocular pressure of ophthalmologically normal dogs

OBJECTIVE

To determine the effect of orally administered melatonin on the intraocular pressure (IOP) of ophthalmologically normal dogs.

ANIMALS

20 ophthalmologically normal dogs (40 eyes).

PROCEDURES

In a randomized crossover study, each dog received a 7-day regimen of melatonin (0.1 to 0.2 mg/kg, PO, q 12 h) and a placebo (150 mg of lactose powder in a capsule, PO, q 12 h), with a 7-day washout period between treatment regimens. Rebound tonometry was used to measure the IOP in both eyes of each dog 5 times at 2-hour intervals on days 0 (before administration of the first dose), 2, 4, and 7 (after administration of the last dose) of each treatment period. Repeated-measures ANOVA was used to evaluate the effects of treatment, day, and IOP measurement time within day on IOP.

RESULTS

Intraocular pressure was not significantly associated with treatment but was associated with day and the interaction between day and IOP measurement time within day. The mean ± SD IOP was 14.26 ± 2.95 and 14.34 ± 2.69 mm Hg for the melatonin and placebo regimens, respectively. Within each treatment period, the mean IOP tended to decrease from day 0 to 7 as well as within each day, which was attributed to the dogs becoming acclimated to the study protocol and natural diurnal variations in IOP.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that oral administration of melatonin (0.1 to 0.2 mg/kg, q 12 h for 7 d) did not significantly affect the IOP of ophthalmologically normal dogs.

Effect of Melatonin on Blood Loss After Cesarean Section: A Prospective Randomized Double-Blind Trial

Background and Objectives

The similarities between the melatonin and oxytocin signaling could lead to increased contractility of myometrium. We designed this randomized double-blind, placebo-controlled trial to evaluate the efficacy of melatonin in reduction of blood loss during and after the lower segment cesarean section.

Methods

One hundred and twenty patients who had been scheduled for cesarean section under spinal anesthesia were enrolled in the study. We randomly allocated them to one of the three following groups to receive either melatonin 3 mg (M₃), melatonin 6 mg (M₆), or placebo (P) sublingually 20 min before the surgery. The hemoglobin levels before and 12 h after surgery, the mean weight of the materials used in the operation time, the need for additional oxytocic therapy, and the incidence of adverse effects were probed and recorded.

Results

There was a significant difference between the group M₆ and both M₃ and P in the mean weight of the materials (p = .024 and .041, respectively) and between M₆ and P groups in terms of mean decrease in hemoglobin during 12 h after cesarean section (p = .029).

Conclusion

Using 6 mg melatonin, sublingually, as a premedication in patients undergoing cesarean section with spinal anesthesia could statistically reduce the amount of blood loss after the lower segment cesarean section, although it may not be clinically meaningful.Registration number: ACTRN12612000117819 and ClinicalTrials.gov Identifier: NCT01572805.

Acute emotional stress as a trigger for intraocular pressure elevation in Glaucoma

Background

Stress-induced activation of the sympathetic nervous system leads to a cascade of metabolic reactions. Emotional stress is a more specific form of stress in which the stressor is a psychological response to a situation subjectively perceived as traumatic. Stress hormones can have a wide range of effects on the body, however, it is still unclear if and how it can affect ophthalmic physiology. This report presents a case of severe ocular hypertension in which emotional stress was the only cause elicited, and explores potential aggravating factors.

Case presentation

A 78-year-old, personality type A, lady with a history of pseudo-exfoliative glaucoma presented with an acute asymmetrical raise in intraocular pressure (IOP) immediately following a family breakdown. Her IOP had previously remained stable following a deep sclerectomy in the right eye and an Ex-PRESS shunt in the left eye. Her examination was entirely normal otherwise, with a patent filtration and diffuse bleb as confirmed with anterior segment OCT imaging. Near-normalisation of her IOP was observed within 24 h, concomitantly with the reduction of her stress levels. No other cause for the transient acute hypertensive episode were found.

Conclusions

This case report suggests that acute emotional stress could severely affect IOP in patients suffering from glaucoma. This could be important when looking after glaucoma patients. It would also suggest that the personnality types, and the emotional and social context are more factors to take into account in glaucoma studies. These observations are based on a single case report and would need to be verified on a larger scale.

Melatonin in Critical Care

Melatonin is involved in regulation of a variety of physiologic functions, including circadian rhythm, reproduction, mood, and immune function. Exogenous melatonin has demonstrated many clinical effects. Numerous clinical studies have documented improved sleep quality following administration of exogenous melatonin. Recent studies also demonstrate the analgesic, anxiolytic, antiinflammatory, and antioxidative effects of melatonin. This article reviews the principal properties of melatonin and how these could find clinical applications in care of the critically ill patients.

Efficacy of Preoperative Administration of Acetaminophen and Melatonin on Retrobulbar Block Associated Pain in Cataract Surgery

Background

Retrobulbar block is one of the chosen methods for local anesthesia in cataract surgery. Since it is a painful procedure, using analgesic and sedative drugs is recommended. Current medications have side effects and evaluating of new drugs or new uses of existing safer drugs is necessary.

Objectives

The aim of this study was to compare the administration of melatonin and acetaminophen on pain and hemodynamic changes during retrobulbar block.

Methods

In a double-blinded randomized trial, 180 patients undergoing cataract surgery were randomly divided into three groups: Melatonin group (received melatonin 6 mg), acetaminophen group (received acetaminophen 500 mg), and control group (received placebo). All drugs were administered orally 60 min before arrival to the operating room by nurses blinded to the drugs administered. All patients received fentanyl 0.5 μg/kg before retrobulbar block intravenously. Hemodynamic variables and pain score in each patient were evaluated on arrival in the operating room, during retrobulbar block, during surgery, 20 min after operation, at the end of surgery, and in the recovery room. In case of pain score more than three, additional fentanyl was administered. All data were recorded in structured data sheets.

Results

Data analysis indicated no significant differences among the groups at baseline on any of the demographic variables. Both acetaminophen and melatonin reduced the pain score significantly compared with control during retrobulbar block (P < 0.05 and P < 0.01, respectively). Administration of additional fentanyl was significantly lower in the melatonin group than the control group (P < 0.05). Hemodynamic changes were not significantly different among all groups.

Conclusions

For the first time, as far as we have studied, the analgesic effect of acetaminophen on the retrobulbar block was indicated. We also showed that melatonin can reduce pain during retrobulbar block leading to reduction of additional fentanyl during operation. It seems that both melatonin and acetaminophen may have a beneficial effect on pain control in the retrobulbar block.