OPTIMAX CAPSULES

Indications

• Management of photosensitivity reactions
• Erythropoietic protoporphyria

Dosage

Children: Child 1–4 years: 60–90 mg daily, Child 5–8 years: 90–120 mg daily, Child 9–11 years: 120–150 mg daily, to be given as a single dose or in divided doses.

Adults: Refer to the BNF for specific dosing guidelines.

Mechanism of action

Betacarotene acts as an antioxidant and a precursor to vitamin A, which plays a critical role in cellular function, vision, growth, immune function, and skin health.

Pharmacodynamics

As a provitamin, betacarotene is converted to retinol (vitamin A) in the body, supporting various biological functions, including the maintenance of epithelial tissues and the modulation of immune responses.

Pharmacokinetics

Betacarotene is absorbed from the gastrointestinal tract and is stored in the liver. Its absorption can be influenced by dietary fat intake. It is primarily metabolized in the liver and has a relatively long half-life due to its storage in fat tissues.

Pregnancy

Safety in pregnancy has not been established; use only if clearly needed.

Breast-feeding

Excretion in breast milk is unknown; use with caution.

Storage

Store in a cool, dry place, away from direct sunlight.

Formulations

• Oral preparations containing beta-carotene

Indications

• Vitamin C deficiency
• Scurvy
• Adjunct therapy in iron overload conditions

Dosage

Children: Child 1 month–3 years: 125–250 mg daily in 1–2 divided doses; Child 4–11 years: 250–500 mg daily in 1–2 divided doses; Child 12–17 years: 0.5–1 g daily in 1–2 divided doses.

Adults: 500 mg daily, taken in 1-2 divided doses, depending on the clinical condition and dietary needs.

Mechanism of action

Ascorbic acid functions primarily as a reducing agent, facilitating enzymatic reactions in the body, including the hydroxylation of proline and lysine in collagen synthesis. It also plays a role in the absorption of iron from the gastrointestinal tract and enhances the immune response.

Pharmacodynamics

Ascorbic acid is crucial for the maintenance of connective tissue and is involved in the metabolism of several amino acids. Its antioxidant properties help to mitigate oxidative stress and may play a role in reducing the risk of chronic diseases.

Pharmacokinetics

Ascorbic acid is absorbed in the intestines and is widely distributed throughout the body. The renal clearance of ascorbic acid is dose-dependent, with higher doses leading to increased excretion. The half-life varies but is generally around 15 to 30 minutes in healthy individuals, with tissue saturation levels influencing its retention.

Contra-indications

• Hypercalcaemia
• Hyperoxaluria
• Patients with cardiac dysfunction

Adverse effects

• Abdominal pain
• Headache
• Nausea
• Vomiting
• Diarrhoea
• Constipation
• Weight loss
• Polyuria
• Sweating
• Thirst
• Vertigo

Interactions

• Increases risk of cardiovascular adverse effects with iron chelators
• Increases risk of cardiovascular adverse effects with deferiprone
• Increases risk of cardiovascular adverse effects with desferrioxamine

Precautions

• Use with caution in patients with iron overload
• Monitor for symptoms of overdose

Pregnancy

High doses teratogenic in animals but therapeutic doses unlikely to be harmful.

Storage

Store in a cool, dry place away from direct sunlight.

Formulations

• Ascorbic acid 50 mg tablets
• Ascorbic acid 100 mg tablets
• Ascorbic acid 200 mg tablets
• Ascorbic acid 250 mg tablets
• Ascorbic acid 500 mg capsules

Indications

• Copper deficiency
• Occipital Horn Syndrome
• Menke's disease
• Contraception (via copper IUD)

Dosage

Children: Refer to the BNF for Children for specific dosing information.

Adults: Refer to the relevant clinical guidelines and BNF for specific dosing information.

Mechanism of action

Copper is absorbed from the gastrointestinal tract via high affinity copper uptake proteins and low affinity copper uptake proteins, likely being reduced to the Cu1+ form prior to transport. Inside enterocytes, it binds to the copper transport protein ATOX1, which facilitates its transport to copper transporting ATPase-1 on the Golgi membrane for incorporation into the Golgi apparatus. Once in systemic circulation, copper binds primarily to ceruloplasmin, albumin, and alpha 2-macroglobulin. It acts as a cofactor in a variety of oxidase enzymes and also influences sperm motility when released from copper IUDs, contributing to its contraceptive effect.

Pharmacodynamics

Copper is essential for the activity of many enzymes and plays a vital role in processes such as iron metabolism, neurotransmitter synthesis, and antioxidant defense. Copper ions, particularly when released from intrauterine devices, have been shown to decrease sperm viability, thereby impacting fertility.

Pharmacokinetics

Copper is absorbed from the gut and is predominantly transported in the plasma bound to proteins such as ceruloplasmin and albumin. The absorption efficiency can vary; however, a significant portion of dietary copper is usually absorbed. The body regulates copper levels through hepatic excretion and storage mechanisms, ensuring homeostasis. Excess copper can lead to toxicity, while deficiency results in various health issues.

Pregnancy

Copper is considered essential during pregnancy, but excessive intake should be avoided due to potential toxicity.

Breast-feeding

Copper is excreted in breast milk, and adequate maternal intake is important for infant development.

Storage

Store in a cool, dry place, away from moisture and heat.

Mechanism of action

Glutathione (GSH) participates in leukotriene synthesis and acts as a cofactor for the enzyme glutathione peroxidase. It plays a critical role in detoxifying lipophilic toxins through conjugation, enhancing their excretion in bile. Glutathione is involved in detoxifying methylglyoxal, a toxic by-product of metabolism, through the glyoxalase enzyme pathway. Glyoxalase I and II catalyze the conversion of methylglyoxal and reduced glutathione to S-D-Lactoyl-glutathione and then to reduced glutathione and D-lactate. GSH is also a cofactor for conjugation reactions mediated by glutathione S-transferase enzymes and can engage in non-enzymatic conjugation with certain reactive metabolites, such as N-acetyl-p-benzoquinone imine (NAPQI), thereby detoxifying them.

Pharmacodynamics

L-glutathione exerts its antioxidant effects by directly scavenging free radicals and reactive oxygen species, thus preventing cellular damage. It also maintains the activity of other antioxidants, such as vitamins C and E, and plays a crucial role in the regeneration of oxidized glutathione. Due to its involvement in various metabolic pathways, including the detoxification of harmful substances, it is essential for overall cellular health and function.

Pharmacokinetics

L-glutathione is absorbed in the gastrointestinal tract, but its bioavailability is variable due to rapid metabolism and degradation in the intestinal lumen. It is distributed throughout the body, with higher concentrations found in the liver, lungs, and erythrocytes. The metabolism of glutathione primarily occurs in the liver, where it undergoes conjugation and is involved in various metabolic pathways. Excretion occurs mainly through biliary routes, and it is also recycled through the action of enzymes that convert

Pregnancy

There is insufficient data on the safety of glutathione during pregnancy. It is advisable to use it only if clearly needed and after assessing the benefits and risks.

Breast-feeding

Limited information is available regarding the excretion of glutathione in human milk. Caution is advised when administering to breastfeeding women.

Storage

Store in a cool, dry place away from direct sunlight. Ensure the container is tightly closed to maintain product stability.

Indications

• Age-related Macular Degeneration (AMD)
• Cataracts
• Ocular health protection
• Antioxidant support

Dosage

Children: Refer to BNF for Children for specific dosage guidance as it may vary based on formulation and clinical indication.

Adults: Refer to BNF for specific dosage guidance as it may vary based on formulation and clinical indication.

Mechanism of action

Lutein exhibits antioxidant activity by reacting with active oxygen species, leading to the production of biologically active degradation products. It inhibits the peroxidation of membrane phospholipids and reduces lipofuscin formation, which are key contributors to oxidative stress. Additionally, lutein filters blue light and near-ultraviolet radiation, providing protective effects in the retina due to its ability to scavenge reactive oxygen species. It also enhances the expression of connexin-43, facilitating gap junctional communication and offering potential protection against cancer.

Pharmacodynamics

Lutein is concentrated in the macula of the retina, where it exerts protective effects against oxidative stress and high-energy light. Its presence is linked to a decreased risk of developing eye diseases such as Age-related Macular Degeneration (AMD). Studies indicate that higher macular pigment density is associated with a reduced risk of these conditions, highlighting lutein's role in maintaining eye health.

Pharmacokinetics

Lutein is absorbed in the gastrointestinal tract and its bioavailability can be influenced by the presence of dietary fats. It is transported in the bloodstream primarily via lipoproteins and is distributed to various tissues, with a significant accumulation in the retina and lenses of the eyes. The elimination half-life and metabolic pathways are not well characterized, but lutein is known to be more stable against degradation by pro-oxidants compared to other carotenoids.

Pregnancy

Lutein is generally considered safe during pregnancy, but consult a healthcare provider for individual assessment.

Breast-feeding

Lutein is likely safe during breastfeeding, but it is advisable to consult a healthcare provider.

Storage

Store in a cool, dry place away from light.

Formulations

• Supplement capsules
• Softgel formulations
• Powdered forms for mixing

Indications

• Manganese deficiency
• Bone health and development
• Antioxidant support
• Enzyme cofactor in metabolic processes

Dosage

Children: Refer to the BNF for Children for appropriate dosing recommendations.

Adults: Refer to specific clinical guidelines or the BNF for appropriate dosing recommendations.

Mechanism of action

Manganese serves as a cofactor for several enzymes, including manganese superoxide dismutase (MnSOD), which protects cells from oxidative stress by catalyzing the dismutation of superoxide radicals into oxygen and hydrogen peroxide. It also participates in the activation of enzymes involved in carbohydrate, fat, and protein metabolism.

Pharmacodynamics

Manganese plays a role in various biochemical pathways, particularly in the metabolism of amino acids, cholesterol, glucose, and carbohydrates. It is crucial for bone formation and the maintenance of cartilage. Manganese also aids in the synthesis of glycosyltransferases, which are important for the formation of glycoproteins and proteoglycans.

Pharmacokinetics

Manganese is absorbed primarily in the small intestine, with absorption efficiency influenced by dietary factors and the presence of competing minerals. It is transported in the bloodstream bound to proteins such as alpha-2-macroglobulin and transferrin. Manganese is stored in the liver, pancreas, and bones, and is excreted primarily through bile and to a lesser extent in urine. Its half-life in the human body is not well defined due to its trace nature and variable absorption.

Pregnancy

Manganese is classified as a dietary mineral that is essential for human health, but excessive intake should be avoided during pregnancy as it may affect fetal development.

Breast-feeding

Manganese is present in breast milk, and normal dietary intake is considered safe during breastfeeding. However, excessive supplementation should be avoided.

Storage

Store in a cool, dry place, away from direct light and moisture.

Dosage

Children: Refer to the specific drug formulation and clinical guidelines for appropriate dosing. Pediatric doses should be carefully calculated based on the active ingredient and the child's age and weight.

Adults: Refer to the specific drug formulation and clinical guidelines for appropriate dosing. Doses can vary widely based on the active ingredient and its clinical application.

Mechanism of action

Pentahydrate forms do not have a specific mechanism of action, as they are typically salts or hydrates of other active compounds. The effectiveness depends on the active ingredient associated with the pentahydrate form, which may engage in various biochemical interactions in the body to exert therapeutic effects. Generally, the release of the active drug from its hydrated form can influence its absorption and subsequent pharmacological activity.

Pharmacodynamics

The pharmacodynamics of pentahydrate forms is determined by their active ingredients. The hydration state can affect the dissolution rate, which in turn influences the onset of action and overall efficacy. Hydrated forms can improve solubility in biological fluids, leading to enhanced absorption and bioavailability in certain cases. The specific pharmacological action, such as receptor binding or enzyme inhibition, will depend on the drug itself rather than the pentahydrate status.

Pharmacokinetics

The pharmacokinetics of pentahydrate forms is influenced by the solubility and stability of the drug. Generally, a hydrated form may result in increased dissolution rates, promoting better absorption in the gastrointestinal tract. The extent and rate of absorption can vary based on the specific pentahydrate and its active ingredient. Distribution, metabolism, and excretion will depend on the nature of the drug itself, including its half-life and the pathways involved in its elimination from the body.

Pregnancy

Safety in pregnancy has not been established. Use only if the potential benefit justifies the risk.

Breast-feeding

Caution is advised. It is unknown if pentahydrate is excreted in human milk.

Storage

Store in a cool, dry place, away from light. Keep out of reach of children.

Indications

• Hypokalemia
• Potassium depletion
• Certain types of arrhythmias
• Prevention of hypokalemia in patients receiving diuretics

Dosage

Children: Refer to established guidelines or consult the BNF for Children for specific dosing recommendations.

Adults: Refer to established guidelines or consult the BNF for specific dosing recommendations.

Mechanism of action

Potassium ions play a crucial role in cellular physiology. They are essential for maintaining the resting membrane potential of cells and are involved in the generation of action potentials in excitable tissues such as neurons and muscle cells. The influx and efflux of potassium ions across cell membranes are critical for normal cardiac and neuromuscular function.

Pharmacodynamics

Potassium functions as an essential intracellular cation, influencing various physiological processes. It helps regulate heart rhythm, muscle contraction, and nerve impulses. An adequate potassium level is necessary to prevent muscle weakness, paralysis, and arrhythmias. The relationship between potassium levels and these physiological functions is tightly controlled by renal function and dietary intake.

Pharmacokinetics

Potassium is absorbed primarily in the gastrointestinal tract. Following absorption, it is distributed throughout the body's tissues, with approximately 98% of the body's potassium found intracellularly. The kidneys play a critical role in regulating potassium levels by excreting excess potassium in urine. The half-life of potassium in the body can vary significantly based on renal function, dietary intake, and cellular demands.

Pregnancy

There is insufficient data on the safety of pentapotassium during pregnancy. It should only be used if the benefits outweigh the risks.

Breast-feeding

It is not known if pentapotassium is excreted in human milk. Caution is advised when administering to nursing mothers.

Storage

Store in a cool, dry place, away from direct sunlight. Keep out of reach of children.

Indications

• Vitamin A deficiency
• Night blindness
• Impaired wound healing
• Epithelial disorders

Dosage

Children: Refer to BNF for Children for specific paediatric dosing information.

Adults: Refer to BNF for specific adult dosing information.

Mechanism of action

Retinol is converted in the retina to 11-cis-retinal, which is crucial for the conversion of light into neural signals necessary for vision. It binds to opsin in rhodopsin, facilitating the isomerization to all-trans-retinal upon exposure to light, thus triggering visual signaling. Additionally, retinol interacts with retinoic acid receptors (RARs) and retinoid-X receptors (RXRs) as transcription factors, modulating gene expression related to cellular differentiation and growth.

Pharmacodynamics

Vitamin A is effective in treating Vitamin A deficiency, which can lead to vision impairment and other health issues. It plays a critical role in various biological processes including vision, cellular differentiation, reproduction, and immune system function. Its deficiency can cause symptoms such as night blindness and impaired wound healing, while adequate levels support growth and development.

Pharmacokinetics

Retinol is absorbed from the gastrointestinal tract and stored in the liver, where it can be mobilized as needed. It undergoes metabolism primarily in the liver, where it is converted to retinal and retinoic acid, the active forms of Vitamin A. The elimination half-life varies, but retinol is generally excreted in urine and bile. The bioavailability can be affected by dietary fat intake.

Adverse effects

• Nausea
• Vomiting
• Headache
• Dizziness
• Fatigue
• Irritability
• Dry skin
• Peeling of skin
• Itching
• Blurred vision

Precautions

• Use with caution in patients with liver disease due to potential hepatotoxicity.
• Monitor for signs of vitamin A toxicity, especially in patients on high doses or prolonged therapy.
• Caution in patients with a history of alcohol abuse, as it may exacerbate liver conditions.

Pregnancy

Retinol should be used with caution during pregnancy due to the risk of teratogenic effects. High doses of vitamin A can lead to fetal malformations.

Breast-feeding

Retinol is generally considered safe during breastfeeding, but excessive intake should be avoided to prevent potential adverse effects on the infant.

Storage

Store in a cool, dry place away from light. Keep out of reach of children.

Formulations

• Capsules
• Tablets
• Oral solutions
• Topical preparations

Indications

• Selenium deficiency
• Antioxidant therapy
• Support in thyroid function
• Potential adjunctive treatment in cancer therapy

Dosage

Children: Refer to the BNF for Children for specific dosing recommendations.

Adults: Refer to the BNF for specific dosing recommendations.

Mechanism of action

Selenite acts as a source of selenium, which is incorporated into selenoproteins. These proteins play essential roles in antioxidant defense, thyroid hormone metabolism, and immune function. The selenium from selenite is metabolized to selenophosphate, which is a precursor for the synthesis of selenoamino acids and subsequently selenoproteins.

Pharmacodynamics

Selenite exhibits antioxidant properties by enhancing the activity of antioxidant enzymes, such as glutathione peroxidase. This helps to reduce oxidative stress in the body. The effects of selenite can vary depending on the dose and duration of exposure, with low doses being beneficial and high doses potentially leading to toxicity.

Pharmacokinetics

Selenite is absorbed in the gastrointestinal tract and is distributed throughout the body, with a preference for high accumulation in the liver, kidney, and muscle tissues. The elimination half-life of selenium varies but is generally a few days. Selenium is primarily excreted through urine, and its metabolism involves conversion to various seleno compounds.

Formulations

• Sodium selenite

Indications

• Prevention of vitamin E deficiency
• Antioxidant therapy
• Support in conditions related to oxidative stress

Dosage

Children: Refer to BNF for Children for specific dosage guidelines.

Adults: Refer to BNF for specific dosage guidelines.

Mechanism of action

Tocopherol acts as a radical scavenger, primarily functioning as an antioxidant for lipid bilayers. It donates hydrogen atoms to free radicals, trapping them and preventing cellular damage. Its effectiveness is influenced by its location within the membrane and its interaction with cytosolic reductants like ascorbate. Tocopherol can trap multiple radicals, including alkyl and peroxy radicals.

Pharmacodynamics

The antioxidant properties of tocopherol lead to significant pharmacodynamic effects, including the inhibition of cell death through modulation of protein kinase C (PKC). Tocopherol also exhibits anti-inflammatory effects, which can be attributed to its influence on cytokines, prostaglandins, prostanoids, and thromboxanes. These interactions may contribute to its protective effects in various pathological conditions.

Pharmacokinetics

Tocopherol is absorbed in the intestines and its bioavailability can be influenced by dietary fat intake. It is transported in the plasma primarily bound to lipoproteins. Tocopherol is stored in adipose tissue and the liver, and its elimination occurs through bile and urine. The half-life of tocopherol can vary depending on the individual's nutritional status and other factors.

Pregnancy

Tocopherol is generally considered safe during pregnancy, but it is advisable to consult a healthcare provider before use.

Breast-feeding

Tocopherol is excreted in breast milk, and while it is considered safe, a healthcare provider should be consulted for specific recommendations.

Storage

Store in a cool, dry place away from direct sunlight.

Indications

• Age-related macular degeneration
• Eye health supplementation
• Antioxidant support

Dosage

Children: Refer to the BNF for Children for specific dosing recommendations.

Adults: Refer to the BNF for specific dosing recommendations.

Mechanism of action

Zeaxanthin acts as a light filter in the retina, protecting the eyes from harmful high-energy light waves like ultraviolet rays. It is believed to neutralize free radicals and reduce oxidative stress, which can contribute to various ocular diseases. Additionally, zeaxanthin is involved in the carotenoid biosynthesis pathways, including its conversion from violaxanthin and its role in various biosynthetic processes.

Pharmacodynamics

Zeaxanthin exhibits antioxidant activity, which helps protect cells from oxidative damage. It is selectively deposited in the macula of the eye, where it contributes to visual acuity and may prevent photochemical damage caused by light exposure. Its presence in the retina aids in filtering blue light and supports overall retinal health.

Pharmacokinetics

Zeaxanthin is absorbed in the gastrointestinal tract after dietary intake, with peak plasma concentrations occurring several hours post-ingestion. It is transported in the bloodstream bound to lipoproteins, and its bioavailability can vary based on dietary fat presence. The half-life of zeaxanthin in the body is not well established but is believed to be several days, as it is stored in the retina and other tissues.

Pregnancy

There is insufficient data on the safety of zeaxanthin during pregnancy. Consult a healthcare provider for advice.

Breast-feeding

Limited data is available on the excretion of zeaxanthin in human milk. Consult a healthcare provider for guidance.

Storage

Store in a cool, dry place, away from direct sunlight.

Formulations

• Dietary supplements
• Ophthalmic preparations

Mechanism of action

Beta-carotene is an antioxidant that presents significant efficacy against the reactive oxygen species singlet oxygen. Beta-carotene acts as a scavenger of lipophilic radicals within the membranes of every cell compartments. It also presents an oxidative modification of LDL. The presence of long chains of conjugated double bonds is responsible for its antioxidative properties by allowing beta-carotene to chelate oxygen-free radicals and dissipate their energy. The chelation of free radicals inhibits the peroxidation of lipids. The effect of beta-carotene in the immune response is thought to be related to the direct effect on the thymus which increases the production of immune cells. IN HEMATOPORPHYRIN PHOTOSENSITIZED MICE BETA-CAROTENE SHOWED PHOTOPROTECTION WAS DUE TO FREE RADICAL SCAVENGING OR SINGLET O QUENCHING BUT ALSO A POSSIBLE ROLE OF 400 NM LIGHT ABSORPTION, A PROPERTY OF BETA-CAROTENE. Beta carotene protects patients with erythropoietic protoporphyria against severe photosensitivity reactions (burning sensation, edema, erythema, pruritus, and/or cutaneous lesions). The drug has no effect on the basic biochemical abnormality of erythropoietic protoporphyria (eg, erythrocyte, plasma, and stool concentrations of protoporphyrins are not altered by the drug). The precise mechanism by which the drug exerts photoprotection has not been established. There is some evidence that photosensitizers may act through the formation of singlet excited oxygen and/or free radicals. Since in vitro studies indicate that beta carotene can quench free radicals and singlet excited oxygen, this may be the mechanism by which the drug acts. It is unlikely that beta carotene acts simply as a filter for the wavelengths of light that induce phototoxic effects. beta-Carotene inhibits UV-B carcinogenesis. beta-Carotene is an excellent quencher of singlet oxygen, and can quench free radicals. beta-Carotene has been shown to quench singlet oxygen/free radical reactions in the skin of porphyric mice, and has been found to quench excited species formed on irradiation of mouse skin by UV-B.

Pharmacodynamics

Oral administration of beta-carotene increases the serum concentration of beta-carotene by 60% but it does not change the concentration found in the heart, liver or kidneys. In vitro studies in hepatocytes have shown that beta-carotene ameliorates oxidative stress, enhances antioxidant activity and decreases apoptosis. Other than the antioxidant activities, some other actions have been correlated to beta-carotene. It is thought to have detoxifying properties, as well as to help increase resistance to inflammation and infection and increase immune response and enhance RNA production.

Mechanism of action

Copper is absorbed from the gut via high affinity copper uptake protein and likely through low affinity copper uptake protein and natural resistance-associated macrophage protein-2. It is believed that copper is reduced to the Cu1+ form prior to transport. Once inside the enterocyte, it is bound to copper transport protein ATOX1 which shuttles the ion to copper transporting ATPase-1 on the golgi membrane which take up copper into the golgi apparatus. Once copper has been secreted by enterocytes into the systemic circulation it remain largely bound by ceruloplasmin (65-90%), albumin (18%), and alpha 2-macroglobulin (12%). Copper is an essential element in the body and is incorporated into many oxidase enzymes as a cofactor. It is also a component of zinc/copper super oxide dismutase, giving it an anti-oxidant role. Copper defiency occurs in Occipital Horn Syndrome and Menke's disease both of which are associated with impaired development of connective tissue due to the lack of copper to act as a cofactor in protein-lysine-6-oxidase. Menke's disease is also associated with progressive neurological impairment leading to death in infancy. The precise mechanisms of the effects of copper deficiency are vague due to the wide range of enzymes which use the ion as a cofactor. Copper appears to reduce the viabilty and motility of spermatozoa. This reduces the likelihood of fertilization with a copper IUD, producing copper's contraceptive effect. The exact mechanism of copper's effect on sperm are unknown. The reason for the less severe reaction when the foreign body is at a distance from the retina has been proposed to be ... that near the retina & its blood vessels there is greater oxygen tension than at a distance, which causes metallic copper to oxidize to toxic copper compounds more rapidly close to or in contact with the retina than at a distance. Furthermore, the abscess formation that is characteristic of copper undergoing oxidation close to the retina & choroiod can be attributed to attraction of polymorphonuclear leukocytes from these nearby vascular tissues, which become heavily infiltrated. Liquefaction & disorganization of the vitreous body has been explained on the basis of copper catalysis of oxidation of ascorbic acid, leading to depolymerization of the hyaluronic acid of the vitreous humor. Changes in protein & hexosamine content have also been related to decrease in viscosity of the vitreous humor. Increased content of amino acids in the vitreous humor has been consistent with proteolysis of the vitreous body, but decreased concentration in the aqueous humor has suggested suppression of secretion of amino acids by the ciliary body under the influence of copper.

Pharmacodynamics

Copper is incorporated into many enzymes throughout the body as an essential part of their function. Copper ions are known to reduce fertility when released from copper-containing IUDs.

Mechanism of action

Glutathione (GSH) participates in leukotriene synthesis and is a cofactor for the enzyme glutathione peroxidase. It also plays a role in the hepatic biotransformation and detoxification process; it acts as a hydrophilic molecule that is added to other lipophilic toxins or wastes prior to entering biliary excretion. It participates in the detoxification of methylglyoxal, a toxic by-product of metabolism, mediated by glyoxalase enzymes. Glyoxalase I catalyzes the conversion of methylglyoxal and reduced glutathione to S-D-Lactoyl-glutathione. Glyoxalase II catalyzes the conversion of S-D-Lactoyl Glutathione to Reduced Glutathione and D-lactate. Glyoxalase I catalyzes the conversion of methylglyoxal and reduced glutathione to S-D-Lactoyl-glutathione. Glyoxalase II catalyzes the conversion of S-D-Lactoyl Glutathione to Reduced Glutathione and D-lactate. GSH is a cofactor of conjugation and reduction reactions that are catalyzed by glutathione S-transferase enzymes expressed in the cytosol, microsomes, and mitochondria. However, it is capable of participating in non-enzymatic conjugation with some chemicals, as it is hypothesized to do to a significant extent with n-acetyl-p-benzoquinone imine (NAPQI), the reactive cytochrome P450 reactive metabolite formed by toxic overdose of acetaminophen. Glutathione in this capacity binds to NAPQI as a suicide substrate and in the process detoxifies it, taking the place of cellular protein sulfhydryl groups which would otherwise be toxically adducted. The preferred medical treatment to an overdose of this nature, whose efficacy has been consistently supported in literature, is the administration (usually in atomized form) of N-acetylcysteine, which is used by cells to replace spent GSSG and allow a usable GSH pool.

Mechanism of action

Xanthophylls have antioxidant activity and react with active oxygen species, producing biologically active degradation products. They also can inhibit peroxidation of membrane phospholipids and reduce lipofuscin formation, both of which contribute to their antioxidant properties. Lutein is naturally present in the macula of the human retina. It filters out potentially phototoxic blue light and near-ultraviolet radiation from the macula. The protective effect is due in part, to the reactive oxygen species quenching ability of these carotenoids. Lutein is more stable to decomposition by pro-oxidants than are other carotenoids such as beta-carotene and lycopene. Lutein is abundant in the region surrounding the fovea, and lutein is the predominant pigment at the outermost periphery of the macula. Zeaxanthin, which is fully conjugated (lutein is not), may offer somewhat better protection than lutein against phototoxic damage caused by blue and near-ultraviolet light radiation. Lutein is one of only two carotenoids that have been identified in the human lens, may be protective against age-related increases in lens density and cataract formation. Again, the possible protection afforded by lutein may be accounted for, in part, by its reactive oxygen species scavenging abilities. Carotenoids also provide protection from cancer. One of the mechanisms of this is by increasing the expression of the protein connexin-43, thereby stimulating gap junctional communication and preventing unrestrained cell proliferation.

Pharmacodynamics

Lutein was found to be present in a concentrated area of the macula, a small area of the retina responsible for central vision. The hypothesis for the natural concentration is that lutein helps protect from oxidative stress and high-energy light. Several studies show that an increase in macula pigmentation decreases the risk for eye diseases such as Age-related Macular Degeneration (AMD).

Mechanism of action

Vision:Vitamin A (all-<i>trans</i> retinol) is converted in the retina to the 11-<i>cis</i>-isomer of retinaldehyde or 11-<i>cis</i>-retinal. 11-<i>cis</i>-retinal functions in the retina in the transduction of light into the neural signals necessary for vision. 11-<i>cis</i>-retinal, while attached to opsin in rhodopsin is isomerized to all-<i>trans</i>-retinal by light. This is the event that triggers the nerve impulse to the brain which allows for the perception of light. All-<i>trans</i>-retinal is then released from opsin and reduced to all-<i>trans</i>-retinol. All-<i>trans</i>-retinol is isomerized to 11-<i>cis</i>-retinol in the dark, and then oxidized to 11-<i>cis</i>-retinal. 11-<i>cis</i>-retinal recombines with opsin to re-form rhodopsin. Night blindness or defective vision at low illumination results from a failure to re-synthesize 11-<i>cis</i> retinal rapidly. Epithelial differentiation: The role of Vitamin A in epithelial differentiation, as well as in other physiological processes, involves the binding of Vitamin A to two families of nuclear retinoid receptors (retinoic acid receptors, RARs; and retinoid-X receptors, RXRs). These receptors function as ligand-activated transcription factors that modulate gene transcription. When there is not enough Vitamin A to bind these receptors, natural cell differentiation and growth are interrupted. Topical vitamin A can reverse the impairment of wound healing seen in patients receiving corticosteroids, perhaps by restoring the normal inflammatory reaction in the wound. The possibility has been suggested that systemic vitamin A could inhibit the anti-inflammatory effect of systemic corticosteroids. Retinol arrested proliferation of cultured neuroblastoma cells at concentrations of 50 um. A correlation existed between inhibition of growth and inhibition of ornithine decarboxylase in both neuroblastoma cells and glioma cells with retinol. In rats exptl-hypervitaminosis A has been shown ... to produce severe damage of the retina, mainly in the pigment epithelium according to electron microscopy. Alcohol dehydrogenase activity was shown to disappear in the pigment epithelium and visual cells ... . /The authors/ have shown that in an experimental cell culture system consisting of carcinogen-treated 10T1/2 cells, both retinoids and all dietary carotenoids examined can reversibly inhibit neoplastic transformation in the post-initiation phase of carcinogenesis. This activity strongly correlates with their ability to increase gap junctional intercellular communication by up-regulating the expression of the gene CX43 (connexin43). Connexins comprise the structural unit of gap junctions, organelles which allow direct transfer of signals, nutrients and waste products between contacting cells. CX43 is the most widely expressed member of the gap junction family of genes, and we have demonstrated that its expression is strongly down-regulated in human cancers and in several premalignant conditions. When several human tumour cell lines were genetically engineered to conditionally express CX43 under the influence of a tetracycline promoter, their neoplastic phenotype was strongly attenuated. Specifically, induced cells were inhibited from growing in an anchorage-independent manner and, additionally, growth as xenografts in immunocompromised animals was also strongly attenuated. Growth inhibition in suspension was associated both with increased G(1) cell-cycle arrest and with increased apoptosis. /The authors/ propose a model whereby junctional communication allows the transfer of growth inhibitory signals from normal to neoplastic cells and that retinoids and carotenoids, by increasing signal transfer, act to prevent cancer.

Pharmacodynamics

Vitamin A is effective for the treatment of Vitamin A deficiency. Vitamin A refers to a group of fat-soluble substances that are structurally related to and possess the biological activity of the parent substance of the group called all-<i>trans</i> retinol or retinol. Vitamin A plays vital roles in vision, epithelial differentiation, growth, reproduction, pattern formation during embryogenesis, bone development, hematopoiesis and brain development. It is also important for the maintenance of the proper functioning of the immune system.

Mechanism of action

Tocopherol acts as a radical scavenger. It mainly acts as an antioxidant for lipid bilayers. Tocopherol's functions depend on the H-atom donating ability, location, and movement within the membrane, as well as the efficiency in the radical recycling by some cytosolic reductants such as ascorbate. Tocopherol actions are related to the trap of radicals, and it has been shown that even in the absence of substituents in the ortho-positions, tocopherol can trap more than two radicals. The type of radicals available for tocopherol are alkyl and peroxy.

Pharmacodynamics

The antioxidant effects of tocopherol can be translated into different changes at the pharmacodynamic level. In vitro studies have shown that this antioxidant activity can produce modification in protein kinase C (PKC) which will later be translated into an inhibition of cell death. Some other derivate effects are the anti-inflammatory properties of tocopherol which can be related to the modulation of cytokines or prostaglandins, prostanoids and thromboxanes.