OSTEODIEN​ ​TABLETS

Indications

• Selenium deficiency
• Supportive therapy in conditions requiring antioxidant support
• Potential adjunct in cancer prevention strategies

Dosage

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

Adults: Initially 100–500 micrograms daily, adjusted according to response and serum levels.

Mechanism of action

Selenium is metabolized to selenophosphate and selenocysteine, which are essential for the synthesis of selenoproteins. This process involves the incorporation of selenium into proteins through a specialized tRNA that recognizes the RNA sequence UGA, which is facilitated by SECIS structures and SBP-2 proteins. Key selenoproteins, like glutathione peroxidases, help protect cells from oxidative damage, thus playing a significant role in reducing the risk of diseases such as atherosclerosis and certain cancers.

Pharmacodynamics

Selenium is incorporated into various selenoproteins that perform essential functions, including antioxidant activity, redox balance, and regulation of thyroid hormones. Its role in antioxidant defense mechanisms is particularly important for protecting cells against reactive oxygen species (ROS). Selenium supplementation has been linked to improved immune function and potential cancer prevention.

Pharmacokinetics

Selenium is absorbed through the gastrointestinal tract, and its bioavailability can vary based on the source and form of selenium. Once absorbed, it is distributed to various tissues, where it is incorporated into selenoproteins. Selenium is primarily excreted through urine, and its half-life can depend on dietary intake and individual metabolism. Selenium status can be assessed through blood levels of selenoproteins and selenium itself.

Adverse effects

• Nausea
• Anaemia
• Aplastic anaemia
• Skin reactions
• Gastrointestinal disorders

Precautions

• Selenium supplementation should not be given unless there is good evidence of deficiency.
• Use caution in patients with a history of hypersensitivity to selenium or its compounds.

Pregnancy

Limited information is available regarding selenium supplementation during pregnancy. Consult specialist sources for guidance.

Breast-feeding

Limited information is available; the effect of selenium on copper levels in milk is conflicting, and its impact on the infant is unknown.

Storage

After opening, store in a refrigerator (2–8°C).

Formulations

• Tablets (e.g., L-Selenomethionine 200 micrograms, SelenoPrecise 100 micrograms)
• Capsules (e.g., Trientine dihydrochloride 250 mg)
• Injection solutions (e.g., Sodium selenite 50 micrograms per 1 ml)

Indications

• Symptomatic relief of mild to moderate osteoarthritis of the knee

Dosage

Children: Refer to the BNF for Children for

Adults: 200–400 mg daily, maximum 6.5 mg/kg per day, or 1250 mg once daily, or 1500 mg once daily dissolved in at least 250 mL of water; review treatment if no benefit after 2–3 months.

Mechanism of action

The mechanism of action of glucosamine in joint health is not entirely clear, but it is believed to involve several pathways. Glucosamine is a precursor for glycosaminoglycans, which are essential for cartilage integrity. It may also reduce inflammation by inhibiting interferon gamma and Nuclear factor kappa B subunit 65 (NF-κB p65), which could improve symptoms of arthritis and joint pain. Upon uptake by living cells, glucosamine reacts with ATP to form glucosamine-6-phosphate, further contributing to glycosaminoglycan synthesis.

Pharmacodynamics

Glucosamine is theorized to provide essential building blocks for the synthesis of glycosaminoglycans, potentially slowing the progression of osteoarthritis and alleviating joint pain. Although some studies have indicated modest improvements in joint pain and function among users, the overall evidence remains inconclusive. Glycosaminoglycans are critical for maintaining cartilage elasticity, strength, and flexibility, which are vital for joint health.

Pharmacokinetics

After oral administration, glucosamine is absorbed in the gastrointestinal tract and transported into the bloodstream, where it is metabolized into various forms, including glucosamine-6-phosphate. The exact pharmacokinetics, such as absorption rate and half-life, remain largely undefined, and much of the data is derived from animal studies. Further research is required to clarify its pharmacokinetic profiles in humans.

Adverse effects

• Constipation
• Diarrhoea
• Fatigue
• Gastrointestinal discomfort
• Headache
• Nausea
• Flushing
• Skin reactions

Interactions

• Glucosamine + warfarin: Severe (increases anticoagulant effect)
• Glucosamine + coumarins: Severe (increases anticoagulant effect)
• Glucosamine + acenocoumarol: Unknown (decreases anticoagulant effect)
• Glucosamine + coumarins: Unknown (decreases anticoagulant effect)

Precautions

• Asthma
• Impaired glucose tolerance
• Predisposition to cardiovascular disease

Pregnancy

Safety during pregnancy has not been established; consult with a healthcare provider.

Breast-feeding

Safety during breastfeeding has not been established; consult with a healthcare provider.

Storage

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

Formulations

• Alateris®
• Dolenio®
• Glusartel®

Indications

• Osteoarthritis
• Joint pain
• Cartilage repair
• Joint health maintenance

Dosage

Children: Refer to healthcare professionals for guidance on dosing in children, as specific pediatric dosing information is not well established.

Adults: Refer to specific product labeling and consult healthcare professionals for guidance on dosing, as dosages can vary based on formulations and clinical guidelines.

Mechanism of action

Chondroitin works primarily by providing the building blocks necessary for the synthesis of glycosaminoglycans, which are critical components of cartilage. It is thought to inhibit the enzymes that break down cartilage, thereby promoting cartilage repair while also exhibiting anti-inflammatory properties. Additionally, chondroitin may enhance the retention of water in the cartilage, improving its elasticity and resilience.

Pharmacodynamics

Chondroitin has been shown to modulate inflammatory responses within the joints and may help to improve joint mobility and reduce pain associated with osteoarthritis. Its effects on cartilage metabolism are believed to contribute to its therapeutic benefits, although the clinical efficacy may vary among individuals. The anti-inflammatory properties may also contribute to a reduction in joint swelling and discomfort.

Pharmacokinetics

Chondroitin is poorly absorbed from the gastrointestinal tract, with bioavailability ranging from 12% to 36%. It is distributed in the extracellular matrix of cartilage and other connective tissues. Metabolism of chondroitin is not well understood, but it is believed to be metabolized in the liver. The elimination half-life in humans is not well defined, and it is primarily excreted via urine as metabolites. The effects of food on its absorption are still under investigation.

Adverse effects

• Nausea
• Diarrhea
• Constipation
• Abdominal pain
• Headache
• Skin reactions

Interactions

• Anticoagulants (e.g., warfarin) - may increase the risk of bleeding
• NSAIDs - may affect the efficacy of these medications

Precautions

• Use with caution in patients with a history of bleeding disorders
• Caution is advised in patients undergoing surgery due to potential bleeding risk
• Patients with shellfish allergies should consult a physician as some chondroitin supplements are derived from marine sources

Pregnancy

There is insufficient reliable information regarding the safety of chondroitin during pregnancy. It is advisable to avoid use unless prescribed by a healthcare professional.

Breast-feeding

It is not known if chondroitin is excreted in human milk. Caution is advised for nursing mothers considering its use.

Storage

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

Formulations

• Capsule
• Tablet
• Powder
• Liquid

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.

Indications

• General wellness support
• Anti-inflammatory effects
• Antioxidant activity
• Digestive aid
• Support for immune function

Dosage

Children: Paediatric dosing should be determined based on the specific extract and its intended use. Consultation with a healthcare provider is recommended for accurate dosing.

Adults: Dosage varies widely depending on the specific extract and formulation. It is essential to follow the manufacturer's instructions or consult a healthcare professional for appropriate dosing.

Mechanism of action

The mechanism of action of herbal extracts can vary significantly based on their constituents. Commonly, they exert their effects through multiple pathways including modulation of neurotransmitter systems, interference with inflammatory processes, or direct antioxidant activity. Some extracts may activate certain receptors or inhibit enzymes related to disease processes.

Pharmacodynamics

The pharmacodynamics of extracts is complex due to the presence of multiple active compounds which can have synergistic or antagonistic effects. These compounds may influence cellular signaling pathways, alter gene expression, or modulate immune response. The overall pharmacological profile is determined by the specific composition of the extract, its concentration, and the biological target it interacts with.

Pharmacokinetics

The pharmacokinetics of extracts involves absorption, distribution, metabolism, and excretion of the active compounds. Generally, herbal extracts are absorbed in the gastrointestinal tract, with bioavailability influenced by factors such as formulation, the presence of food, and individual metabolic differences. Compounds may undergo hepatic metabolism, and elimination can occur through urine or feces, depending on their chemical nature.

Pregnancy

Consult a healthcare professional before use, as the safety of the extract during pregnancy has not been established.

Breast-feeding

Consult a healthcare professional before use, as the safety of the extract during breastfeeding has not been established.

Storage

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

Indications

• Folic acid deficiency
• Megaloblastic anemia

Mechanism of action

Folic acid, being biochemically inactive, is converted to tetrahydrofolic acid and methyltetrahydrofolate by dihydrofolate reductase (DHFR). These active forms are then transported into cells where they assist in erythropoiesis, purine and thymidylate synthesis, amino acid interconversion, and the methylation of tRNA. Furthermore, folic acid, with vitamin B12 as a cofactor, aids in normalizing high homocysteine levels by remethylating homocysteine to methionine. The principal biochemical function of folates involves mediating one-carbon transfer reactions, which are crucial for DNA synthesis and repair.

Pharmacodynamics

Folic acid is essential for the synthesis of nucleic acids and the metabolism of amino acids. Its deficiency can result in impaired thymidylate synthesis, leading to defective DNA synthesis, which is associated with megaloblastic and macrocytic anemias. Folic acid is particularly important during periods of rapid cell division and plays a role in cancer protection. As humans cannot synthesize folic acid, dietary intake or supplementation is necessary to prevent deficiencies.

Pharmacokinetics

Folic acid is absorbed primarily in the jejunum of the small intestine, with bioavailability influenced by food composition and other factors. Once absorbed, it is converted to its active forms in the liver and other tissues. The elimination of folate occurs through renal excretion, with a small proportion undergoing enterohepatic recirculation. Adequate intake is essential to maintain optimal levels in the body, especially during increased physiological demands.

Adverse effects

• Allergic reactions
• Rash
• Itching
• Nausea
• Abdominal pain
• Loss of appetite
• Flatulence
• Sleep disturbances

Interactions

• Antiepileptic drugs (e.g., phenytoin) may reduce the effectiveness of folic acid.
• Methotrexate may interfere with folic acid metabolism.
• Sulfasalazine may decrease folate absorption.

Precautions

• Monitor for signs of folate deficiency in patients on long-term medications that interfere with folate metabolism.
• Caution in patients with a history of hypersensitivity to folic acid or its components.

Pregnancy

Folic acid is essential during pregnancy to reduce the risk of neural tube defects and supports fetal development. Recommended supplementation is advised.

Breast-feeding

Folic acid is safe during breastfeeding. Adequate levels are important for both maternal health and infant development.

Storage

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

Formulations

• Tablets
• Syrups
• Injectable formulations

Indications

• Nausea and vomiting (including motion sickness and morning sickness)
• Gastrointestinal discomfort
• Osteoarthritis
• Inflammation
• Cold and flu symptoms

Dosage

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

Adults: Refer to established guidelines for specific dosing; typically, doses range from 1 to 3 grams of dried ginger per day.

Mechanism of action

The active components of ginger, particularly gingerols, exert their effects primarily through the inhibition of pro-inflammatory cytokines and enzymes, such as cyclooxygenase and lipoxygenase. This action helps to reduce inflammation and pain. Additionally, ginger enhances gastrointestinal motility and has antiemetic properties, which are beneficial in treating nausea.

Pharmacodynamics

Ginger exhibits anti-inflammatory, antioxidant, and antinausea effects. Its ability to modulate the immune response and inhibit platelet aggregation contributes to its cardiovascular protective effects. The antiemetic properties of ginger are particularly effective in reducing nausea and vomiting associated with motion sickness and chemotherapy.

Pharmacokinetics

Ginger is rapidly absorbed in the gastrointestinal tract, with its active components being metabolized in the liver. The bioavailability of ginger compounds may vary, with gingerols being converted into shogaols during processing or heating. The elimination half-life and specific metabolic pathways have not been extensively studied, but the effects can be observed within 30 minutes to 2 hours after ingestion.

Contra-indications

• Gallstones
• Bleeding disorders
• Allergy to ginger or other plants in the Zingiberaceae family

Adverse effects

• Gastrointestinal disturbances (nausea, diarrhea, heartburn)
• Allergic reactions (skin rash, itching)
• Increased risk of bleeding

Interactions

• Anticoagulants (e.g., warfarin, aspirin)
• Antiplatelet agents
• Certain antihypertensives
• Diabetes medications (may enhance effects)

Precautions

• Use with caution in patients with diabetes, hypertension, or gallbladder disease
• Consult a healthcare provider before use in pregnancy or lactation

Pregnancy

Generally considered safe in food amounts, but high doses should be avoided due to potential effects on uterine contractions.

Breast-feeding

Considered safe in food amounts, but high doses should be avoided.

Storage

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

Formulations

• Dried ginger powder
• Ginger root (fresh)
• Ginger tea
• Ginger extract (liquid or capsule)
• Ginger oil

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 specific formulations and preparations for recommended dosing in children, as it varies widely by plant and intended use.

Adults: Refer to specific formulations and preparations for recommended dosing, as it varies widely by plant and intended use.

Mechanism of action

The mechanism of action varies significantly depending on the specific root being referred to. Many plant roots contain bioactive compounds such as alkaloids, flavonoids, and glycosides, which can modulate various biochemical pathways in the body. For instance, certain roots may inhibit enzymes involved in inflammation or microbial growth, while others may enhance immune responses or modulate neurotransmitter activity.

Pharmacodynamics

Pharmacodynamics will differ based on the specific root and its active compounds. Generally, roots may exhibit anti-inflammatory, analgesic, antimicrobial, or antioxidant effects. The pharmacodynamic profile will also depend on factors such as dosage, preparation method (e.g., decoction, tincture), and the specific condition being treated. For example, some roots may interact with cellular receptors, while others may exert their effects through modulation of gene expression.

Pharmacokinetics

The pharmacokinetics of a root extract will vary with the specific plant. Typically, factors such as absorption, distribution, metabolism, and excretion are influenced by the chemical composition of the root, the method of preparation, and the route of administration. Many active compounds are absorbed in the gastrointestinal tract, metabolized in the liver, and excreted via urine or feces. The bioavailability of these compounds can be affected by their solubility and stability.

Pregnancy

The safety of root during pregnancy has not been established. Consult a healthcare professional before use.

Breast-feeding

It is unknown whether root is excreted in human milk. Caution is advised when administering to nursing mothers.

Storage

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

Mechanism of action

The mechanism of action of glucosamine in joint health is unclear, however there are several possible mechanisms that contribute to its therapeutic effects. Because glucosamine is a precursor for glycosaminoglycans, and glycosaminoglycans are a major component of joint cartilage, glucosamine supplements may help to rebuild cartilage and treat the symptoms of arthritis. Some in vitro studies show evidence that glucosamine reduces inflammation via inhibition of interferon gamma and Nuclear factor kappa B subunit 65 (NF-κB p65), improving the symptoms of arthritis and joint pain. Clinical relevance is unknown at this time. When taken up by living cells, glucosamine reacts with ATP to form glucosamine-6-phosphate, the natural precursor of glycosaminoglycans (GAGs) that contain N-acetylglucosamine (keratan sulfate and Hyaluronan) and those that have N-acetylgalactosamine (heparan sulfate and chondroitin sulfate). These GAGs are polysaccharides composed of hexosamines and monosaccharides (e.g., galactose and glucuronic acid) arranged as a linear chain of repeating disaccharide units (such as the glucuronic acid and N-acetylgalactosamine-6-sulfate of chondroitin sulfate). With the exception of hyaluronan, GAGs do not exist alone in nature but are attached to specific "core" proteins, and the composite structures are called proteoglycans (protein-glycosaminoglycans). Both hyaluronan and many different kinds of proteoglycans (such as aggrecan, versican, and syndecan) are abundant throughout the body where they perform diverse functions.

Pharmacodynamics

The administration of glucosamine, in theory, provides a building block towards the synthesis of glycosaminoglycans, slowing the progression of osteoarthritis and relieving symptoms of joint pain. Studies to this date examining the efficacy of glucosamine sulfate have been inconclusive. Glycosaminoglycans contribute to joint cartilage elasticity, strength, and flexibility. A systematic review of various studies and guidelines determined that modest improvements were reported for joint pain and function in patients taking glucosamine. A consistent joint space narrowing was observed, but with an unclear clinical significance.

Mechanism of action

Selenium is first metabolized to selenophosphate and selenocysteine. Selenium incorporation is genetically encoded through the RNA sequence UGA. This sequence is recognized by RNA ste loop structures called selenocysteine inserting sequences (SECIS). These structures require the binding of SECIS binding proteins (SBP-2) to recognize selenocystiene. The specialized tRNA is first bound to a serine residue which is then enzymatically processed to a selylcysteyl-tRNA by selenocystiene sythase using selenophosphate as a selenium donor. Other unidentified proteins are required as part of the binding of this tRNA to the ribosome. Selenoproteins appear to be necessary for life as mice with the specialized tRNA gene knocked out exhibited early embryonic lethality. The most important selenoproteins seem to be the glutathione peroxidases and thioredoxin reductases which are part of the body's defenses againts reactive oxygen species (ROS). The importance of selenium in these anti-oxidant proteins has been implicated in the reduction of atherosclerosis by preventing the oxidation of low density lipoprotein. Selenium supplementation is also being investigated in the prevention of cancer and has been suggested to be beneficial to immune function. Converging data from epidemiological, ecological, and clinical studies have shown that selenium (Se) can decrease the risk for some types of human cancers. Induction of apoptosis is considered an important cellular event that can account for the cancer preventive effects of Se. Prior to occurrence of apoptosis, Se compounds alter the expression and/or activities of signaling molecules, mitochondria-associated factors, transcriptional factors, tumor suppressor genes, and cellular reduced glutathione. Mechanistic studies have demonstrated that the methylselenol metabolite pool has many desirable attributes of chemoprevention, whereas the hydrogen selenide pool with excess of selenoprotein synthesis can lead to DNA single-strand breaks. To elucidate the effects of Se on cytotoxic events, it should be remembered that the chemical forms and the dose of Se, and the experimental system used, are determinants of its biological activities. This mini-review focuses on elucidation of the molecular mechanisms of cancer prevention by Se with the apoptotic approach. /Selenium/ Selenium status can also influence thyroid hormone function via the deiodinase enzymes. Selenium is a critical component of the deiodinase enzymes, including iodothyronine 5'-deiodinases, which convert the prohormone thyroxine (T4) to the active circulating form, triiodothyronine (T3). Selenium is also a component of GPX, the main enzyme responsible for protecting thyroid cells against oxidative damage. GPX is involved in the detoxification of hydrogen peroxide, which is produced in the thyroid during the conversion of T4 to T3. /Selenium/ Selenium readily substitutes for sulfur in biomolecules and in many biochemical reactions, especially when the concentration of selenium is high and the concentration of sulfur is low in the organism. Inactivation of the sulfhydryl enzymes necessary for oxidative reactions in cellular respiration, through effects on mitochondrial and microsomal electron transport, might contribute to acute selenium toxicity. Selenium may have a role in hepatic heme metabolism that is related to GPX or lipid peroxidation. Selenocysteine is specifically found in some proteins (e.g., glutathione peroxidase); selenomethionine appears to randomly substitute for methionine in protein synthesis. This appears to be an additional mechanism for intermediate- or chronic-duration toxicity. Skin, hair, and nail damage are significant indicators of chronic selenium overexposure. The mechanism causing these integumentary effects is unclear, but could be related to the high selenium concentrations in these tissues as a consequence of the substitution of selenium for sulfur in certain amino acids, including the disulfide bridges that pr

Pharmacodynamics

Selenium is incorporated into many different selenoproteins which serve various functions throughout the body.

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

Folic acid, as it is biochemically inactive, is converted to tetrahydrofolic acid and methyltetrahydrofolate by dihydrofolate reductase (DHFR). These folic acid congeners are transported across cells by receptor-mediated endocytosis where they are needed to maintain normal erythropoiesis, synthesize purine and thymidylate nucleic acids, interconvert amino acids, methylate tRNA, and generate and use formate. Using vitamin B12 as a cofactor, folic acid can normalize high homocysteine levels by remethylation of homocysteine to methionine via methionine synthetase. Folic acid, after conversion to tetrahydrofolic acid, is necessary for normal erythropoiesis, synthesis of purine and thymidylates, metabolism of amino acids such as glycine and methionine, and the metabolism of histidine. The principal biochemical function of folates is the mediation of one-carbon transfer reactions. 5-Methyltetrahydrofolate donates a methyl group to homocystine, in the conversion of homocystine to L-methionine. ... 5,10-Methyltetrahydrofolate is regenerated from tetrahydrofolate via the enzyme serine hydroxymethyltransferase, a reaction, which in addition to producing 5,10-methyltetrahydrofolate, yields glycine. ... 5,10-methyltetrahydrofolate, supplies the one carbon group for the methylation of deoxyuridylic acid to form the DNA precursor thymidylic acid. This reaction is catalyzed by thymidylate synthase and the folate product of the reaction is dihydrofolate. Dihydrofolate is converted to tetrahydrofolate via the enzyme dihydrofolate reductase ...

Pharmacodynamics

Folic acid is a water-soluble B-complex vitamin found in foods such as liver, kidney, yeast, and leafy, green vegetables. Also known as folate or Vitamin B9, folic acid is an essential cofactor for enzymes involved in DNA and RNA synthesis. More specifically, folic acid is required by the body for the synthesis of purines, pyrimidines, and methionine before incorporation into DNA or protein. Folic acid is the precursor of tetrahydrofolic acid, which is involved as a cofactor for transformylation reactions in the biosynthesis of purines and thymidylates of nucleic acids. Impairment of thymidylate synthesis in patients with folic acid deficiency is thought to account for the defective deoxyribonucleic acid (DNA) synthesis that leads to megaloblast formation and megaloblastic and macrocytic anemias. Folic acid is particularly important during phases of rapid cell division, such as infancy, pregnancy, and erythropoiesis, and plays a protective factor in the development of cancer. As humans are unable to synthesize folic acid endogenously, diet and supplementation is necessary to prevent deficiencies. In order to function properly within the body, folic acid must first be reduced by the enzyme dihydrofolate reductase (DHFR) into the cofactors dihydrofolate (DHF) and tetrahydrofolate (THF). This important pathway, which is required for de novo synthesis of nucleic acids and amino acids, is disrupted by anti-metabolite therapies such as [DB00563] as they function as DHFR inhibitors to prevent DNA synthesis in rapidly dividing cells, and therefore prevent the formation of DHF and THF. In general, folate serum levels below 5 ng/mL indicate folate deficiency, and levels below 2 ng/mL usually result in megaloblastic anemia.