Duo Cox WSP 100g

Indications

• Vitamin K deficiency
• Coagulation disorders due to vitamin K deficiency
• Reversal of anticoagulation in patients on warfarin therapy
• Neonatal prophylaxis of vitamin K deficiency bleeding

Dosage

Adults: For adults, the typical dosage is 1-5 mg administered orally or via slow intravenous injection. Dosing may be adjusted based on clinical response and INR levels.

Mechanism of action

Vitamin K acts as a cofactor for the enzyme gamma-carboxylase, which catalyzes the carboxylation of specific glutamic acid residues on clotting factors II (prothrombin), VII, IX, and X. This carboxylation allows these factors to bind calcium ions, which is essential for their activation and subsequent role in the coagulation cascade. Additionally, vitamin K is involved in carboxylating matrix proteins in chondrocytes, possibly influencing bone density and vascular calcification.

Pharmacodynamics

Phytomenadione is indicated in the management of coagulation disorders resulting from vitamin K deficiency. It promotes the hepatic biosynthesis of prothrombin and other clotting factors, restoring normal clotting function. Its long duration of action and wide therapeutic index make it a safe option for patients requiring vitamin K supplementation, but monitoring of prothrombin time is essential during therapy. Hypersensitivity reactions may occur, especially with parenteral administration.

Pharmacokinetics

Phytomenadione is absorbed in the intestine and transported in the lymphatic system. It is then stored in the liver and released into circulation as needed for clotting factor synthesis. Vitamin K has a long half-life, allowing for sustained action, and is cycled in the body, contributing to its prolonged effects. The elimination occurs primarily through the hepatic pathway, and caution is advised in patients with hepatic impairment.

Contra-indications

• Hypersensitivity to phytomenadione or any of its excipients
• Severe hepatic impairment
• Hyperbilirubinaemia in neonates
• Known risk of hemolytic anemia in newborns

Adverse effects

• Anaphylactoid reactions (especially with intravenous use)
• Hypersensitivity reactions
• Flushing
• Rash
• Gastrointestinal disturbances

Interactions

• Anticoagulants (e.g., warfarin) - may require dose adjustment
• Cholestyramine - may reduce absorption of vitamin K
• Mineral oil - may interfere with absorption
• Antibiotics (e.g., cephalosporins) - may affect vitamin K synthesis by gut flora

Precautions

• Use with caution in patients with G6PD deficiency due to risk of hemolysis
• Monitor INR closely in patients with hepatic impairment
• Use intravenous preparations slowly to avoid vascular collapse
• Caution in elderly patients due to altered pharmacokinetics

Pregnancy

Use only if potential benefit outweighs risk, especially in late pregnancy due to risk of neonatal hemolytic anemia.

Breast-feeding

Present in breast milk; caution is advised if large doses are administered.

Storage

Store at room temperature, away from light and moisture. Protect from freezing.

Formulations

• Capsules (200 units, 400 units)
• Oral solutions
• Tablets (10 mg)
• Injectable solution for intravenous use

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

• Bacterial infections
• Urinary tract infections
• Respiratory tract infections
• Certain types of meningitis

Dosage

Children: Refer to the BNF for Children for appropriate dosing based on the child's age and weight.

Adults: Refer to the BNF for specific dosing information based on the type of infection and patient factors.

Mechanism of action

Sulfadimerazine inhibits the enzymatic conversion of pteridine and p-aminobenzoic acid (PABA) to dihydropteroic acid by competing with PABA for binding to dihydrofolate synthetase. This inhibition reduces the synthesis of tetrahydrofolic acid (THF), which is essential for nucleotide synthesis, ultimately leading to impaired bacterial growth.

Pharmacodynamics

Sulfadimerazine is a bacteriostatic agent that decreases bacterial nucleic acid synthesis through the inhibition of dihydrofolic acid production. By competing with PABA, it prevents the formation of dihydropteroic acid, a crucial step in folate metabolism, thus inhibiting the growth of susceptible bacteria.

Pharmacokinetics

Sulfadimerazine is absorbed well following oral administration, with peak plasma concentrations typically occurring within a few hours. The drug is distributed widely throughout the body tissues and can cross the placenta. It is metabolized in the liver and excreted primarily through the kidneys. The half-life can vary depending on factors such as age, renal function, and concurrent medications.

Adverse effects

• Hypersensitivity reactions
• Gastrointestinal disturbances
• Hematologic disorders such as agranulocytosis
• Renal toxicity
• Skin reactions including Stevens-Johnson syndrome

Interactions

• May interact with anticoagulants, increasing their effects
• May enhance the effects of methotrexate
• Concurrent use with other drugs that can cause bone marrow suppression may increase the risk of hematologic toxicity

Precautions

• Use with caution in patients with renal impairment
• Monitor for signs of blood dyscrasias
• Assess for history of hypersensitivity to sulfonamides or related drugs

Pregnancy

Use during pregnancy only if the potential benefits justify the risks to the fetus, as sulfonamides may cross the placenta.

Breast-feeding

Consider the potential for serious adverse effects in nursing infants; caution is advised.

Storage

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

Formulations

• Tablets
• Oral suspension

Mechanism of action

Vitamin K is a cofactor of gamma-carboxylase. Gamma carboxylase attaches carboxylic acid functional groups to glutamate, allowing precursors of factors II, VII, IX, and X to bind calcium ions. Binding of calcium ions converts these clotting factors to their active form, which are then secreted from hepatocytes into the blood, restoring normal clotting function. Vitamin K may also carboxylate matrix proteins in chondrocytes, inhibiting calcification of joints, and may increase type II collagen. The role of vitamin K in osteroarthritis, bone density, and vascular calcification is currently under investigation. Vit k is necessary for formation of prothrombinogen & other blood clotting factors in liver. During clotting, circulating prothrombin is required for production of thrombin; in turn, thrombin converts fibrinogen to fibrin, network of which constitutes clot. /vit k/ In normal animals and man, phyltonadione ... /is/ virtually devoid of pharmacodynamic activity. In Animals and man deficient in vitamin k, the pharmacological action of vitamin k is identical to its normal physiological function, that is, to promote hepatic biosynthesis of prothrombin (factor ii), proconvertin (factor vii), plasma thromboplastin component (ptc, christmas factor, factor ix), and Stuart factor (factor x). On the basis of studies of microsomal metabolism in vitro and studies in rats and mice in vivo, /it was suggested/ that vitamin K may be mutagenic by affecting the mixed-function oxidase system which metabolizes benzo(a)pyrene. Phylloquinone at a high concentration (200 umol/l) inhibited the conversion of benzo(a)pyrene to its more polar metabolites, ... . Paradoxically, at a lower concentration of phylloquinone (25 umol/l), ... the metabolism of benzo(a)pyrene was increased. In this system, therefore, .... phylloquinone could either potentiate or inhibit it, depending on the concentration. This overall weaker inhibitory effect of phylloquinone could be due to the low solubility of this lipophilic compound, but it is difficult to explain the mechanism of the enhanced metabolism of benzo(a)pyrene at lower concentrations of phylloquinone.

Pharmacodynamics

Phylloquinone is a vitamin K indicated in the treatment of coagulation disorders due to faulty formation of coagulation factors II, VII, IX, and X caused by deficiency or interference in the activity of vitamin K. It has a long duration of action as vitamin K is cycled in the body, and a wide therapeutic index as large doses can be tolerated. Patients should have their prothrombin time monitored during therapy and healthcare professionals should be aware of the increased risk of hypersensitivity reactions with parenteral administration.

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

Sulfonamides inhibit the enzymatic conversion of pteridine and p-aminobenzoic acid (PABA) to dihydropteroic acid by competing with PABA for binding to dihydrofolate synthetase, an intermediate of tetrahydrofolic acid (THF) synthesis. THF is required for the synthesis of purines and dTMP and inhibition of its synthesis inhibits bacterial growth. Pyrimethamine and trimethoprim inhibit dihydrofolate reductase, another step in THF synthesis, and therefore act synergistically with the sulfonamides.

Pharmacodynamics

Sulfamethazine is a sulfonamide drug that inhibits bacterial synthesis of dihydrofolic acid by competing with para-aminobenzoic acid (PABA) for binding to dihydropteroate synthetase (dihydrofolate synthetase). Sulfamethazine is bacteriostatic in nature. Inhibition of dihydrofolic acid synthesis decreases the synthesis of bacterial nucleotides and DNA.