Urpinol 300mg Tablets

Indications

• Dry eye conditions
• Keratoconjunctivitis sicca
• Unstable tear film

Dosage

Children: Apply 3–4 times a day or when required to the eye.

Adults: Apply 3–4 times a day or when required to the eye.

Mechanism of action

Carmellose sodium acts as a viscosity-increasing agent, providing lubrication and hydration. It works by creating a gel-like consistency that mimics natural tears, thus improving moisture retention on the ocular surface. This action alleviates dryness and irritation in the eyes.

Pharmacodynamics

Carmellose sodium exhibits mucomimetic properties, which means it has the ability to mimic natural mucus in the eye. Its effectiveness in reducing symptoms of dryness is attributed to its ability to increase tear film stability and provide a protective barrier against environmental irritants. It does not have systemic effects as it is used topically.

Pharmacokinetics

Carmellose sodium is administered topically and is not absorbed systemically, making its pharmacokinetics primarily local. The onset of action is rapid, providing immediate relief for dry eye symptoms. The duration of action depends on factors such as the formulation and frequency of administration. Due to its high molecular weight, it remains on the ocular surface for an extended period, ensuring prolonged lubrication.

Adverse effects

• Transient blurred vision
• Eye irritation
• Allergic reactions

Precautions

• Consult a healthcare professional if symptoms persist
• Avoid contact with the tip of the dropper to prevent contamination

Pregnancy

Carmellose sodium is generally considered safe for use during pregnancy. However, consult a healthcare provider for personalized advice.

Breast-feeding

Carmellose sodium is not known to pose a risk during breastfeeding, but it is advisable to consult a healthcare provider.

Storage

Store at room temperature, away from direct sunlight. Keep out of reach of children.

Formulations

• Carmize 0.5% eye drops
• Carmize 1% eye drops
• Cellusan 0.5% eye drops
• Celluvisc 0.5% eye drops
• Liquivisc 0.25% eye gel
• Ocu-Lube Carmellose 0.5% eye drops
• Tearvis 0.5% eye drops

Indications

• Prophylaxis of hyperuricaemia associated with cancer chemotherapy
• Prophylaxis of hyperuricaemic nephropathy
• Management of gout
• Treatment of conditions associated with increased uric acid production (e.g., Lesch-Nyhan syndrome)

Dosage

Children: Child 1 month–14 years: 10–20 mg/kg daily, maximum 400 mg per day; Child 15–17 years: Initially 100 mg daily, increased according to response up to 900 mg daily.

Adults: Initially 100 mg daily, increased gradually according to uric acid levels; maximum 900 mg daily in divided doses.

Mechanism of action

Allopurinol inhibits xanthine oxidase, an enzyme involved in the conversion of hypoxanthine to xanthine and xanthine to uric acid, thereby reducing uric acid production.

Pharmacodynamics

By lowering uric acid levels, allopurinol helps to prevent gout attacks and the formation of uric acid crystals in the kidneys, which can lead to nephropathy. It may also reduce hyperuricaemia associated with chemotherapy.

Pharmacokinetics

Allopurinol is well absorbed from the gastrointestinal tract. It has a half-life of about 1 to 2 hours, but its active metabolite, oxypurinol, has a longer half-life and contributes to its pharmacological effects. Excretion is primarily renal.

Contra-indications

• G6PD deficiency
• Hypersensitivity to allopurinol or any of its components

Adverse effects

• Rash (discontinue therapy; if rash mild, re-introduce cautiously but discontinue with cytotoxic drugs immediately if recurrence)
• Hypersensitivity
• Nausea
• Vomiting
• Agranulocytosis
• Alopecia
• Angina pectoris
• Angioedema
• Aplastic anemia
• Asthenia
• Ataxia
• Boils
• Gastrointestinal disorders
• Headache
• Hepatic disorders
• Hyperlipidemia
• Hypertension
• Infertility (male)
• Malaise
• Oedema
• Paraesthesia
• Paralysis
• Severe cutaneous adverse reactions (SCARs)
• Skin reactions
• Stomatitis
• Taste altered
• Thrombocytopenia
• Vertigo
• Visual impairment

Interactions

• Allopurinol + azathioprine: Increased risk of haematological toxicity
• Allopurinol + capecitabine: Decreases effects
• Allopurinol + mercaptopurine: Increased risk of haematological toxicity
• Allopurinol + penicillins: Increased risk of skin rash
• Allopurinol + amoxicillin: Increased risk of skin rash
• Allopurinol + ampicillin: Increased risk of skin rash
• Allopurinol + pyrazinamide: Increased risk of hyperuricaemia
• Thiazide diuretics + allopurinol: Increased risk of hypersensitivity reactions

Precautions

• Monitor closely for hypersensitivity
• Ensure adequate fluid intake
• Allopurinol treatment should be started before cancer therapy

Pregnancy

Not known to be harmful; benefit outweighs risk.

Breast-feeding

Presence in milk unknown but benefit outweighs risk.

Storage

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

Indications

• Dry eye syndrome
• Ocular lubrication
• Gastroesophageal reflux disease (GERD)
• Topical applications (as a lubricant or protectant)

Dosage

Children: Refer to specific formulation guidelines for recommended dosages, as doses vary widely depending on the formulation and intended use.

Adults: Refer to specific formulation guidelines for recommended dosages, as doses vary widely depending on the formulation and intended use.

Mechanism of action

Carmellose works by increasing the viscosity of solutions and forming a gel-like consistency when mixed with water. This property allows it to act as a lubricant and protectant, particularly in formulations designed for ocular or gastrointestinal use. The water-binding capacity of carmellose helps to retain moisture in tissues, which can be beneficial in treating dryness.

Pharmacodynamics

The pharmacodynamic properties of carmellose are primarily related to its ability to modify the physical properties of solutions and suspensions. It does not exert specific pharmacological effects but rather enhances the bioavailability and stability of active ingredients in pharmaceutical formulations. Its hydrophilic nature allows it to hold water and improve the consistency of products, thus facilitating drug delivery and absorption.

Pharmacokinetics

Carmellose is not absorbed systemically when administered orally, as it is primarily used as an excipient. It passes through the gastrointestinal tract without significant metabolism. The elimination half-life is not applicable, as it does not enter systemic circulation. Its effects are localized to the site of application or ingestion, where it acts as a bulking agent or thickener.

Adverse effects

• Gastrointestinal discomfort
• Bloating
• Diarrhea

Precautions

• Use with caution in patients with gastrointestinal disorders
• Monitor for hypersensitivity reactions

Pregnancy

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

Breast-feeding

Carmellose is considered safe for use during breastfeeding, but it is recommended to seek advice from a healthcare professional.

Storage

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

Formulations

• Powder
• Tablet
• Capsule
• Suspension

Indications

• Constipation
• Dietary fiber supplementation
• Irritable bowel syndrome
• Diverticular disease
• Weight management

Dosage

Children: Refer to appropriate guidelines for specific dosage; generally taken with adequate fluid intake.

Adults: Refer to appropriate guidelines for specific dosage; generally taken with adequate fluid intake.

Mechanism of action

Cellulose acts primarily as a bulk-forming laxative. It absorbs water in the intestines, which increases stool bulk and stimulates peristalsis, thus facilitating bowel movements. Additionally, cellulose is not digestible by human enzymes, leading to fermentation by gut bacteria, which may enhance gut health and alter gut microbiota composition.

Pharmacodynamics

Cellulose increases stool weight and frequency of bowel movements. It works by retaining water in the intestines, leading to softer stools and improved passage through the gastrointestinal tract. The bulking effect of cellulose can help alleviate constipation and promote overall digestive health. It may also play a role in cholesterol reduction and glycemic control through its effects on digestion and absorption of nutrients.

Pharmacokinetics

Cellulose is not absorbed into the bloodstream due to its indigestible nature. Instead, it passes through the gastrointestinal tract, where it adds bulk to the stool. Its fermentation by colonic bacteria produces short-chain fatty acids, which may have beneficial effects on colon health. The onset of action for cellulose as a laxative can vary but is generally within 24 to 72 hours after ingestion.

Adverse effects

• Bloating
• Flatulence
• Diarrhea
• Abdominal discomfort

Precautions

• Use with caution in patients with a history of gastrointestinal disorders.
• Monitor for potential allergic reactions in sensitive individuals.

Pregnancy

Cellulose is generally considered safe during pregnancy as it is a non-toxic, indigestible fiber.

Breast-feeding

Cellulose is also considered safe during breastfeeding; it is excreted in breast milk in negligible amounts.

Storage

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

Formulations

• Powder
• Capsules
• Tablets
• Granules

Indications

• Hypovolemic shock
• Severe burns
• Postoperative fluid replacement
• Sepsis
• Trauma management

Dosage

Children: Refer to established guidelines for specific dosing, as it varies based on the type of colloidal solution used and the clinical condition being treated.

Adults: Refer to established guidelines for specific dosing, as it varies based on the type of colloidal solution used and the clinical condition being treated.

Mechanism of action

Colloidal solutions work by maintaining oncotic pressure in the blood, thus helping to retain fluid within the vascular system. This is primarily due to the large molecular weight of the colloidal particles, which cannot easily pass through capillary walls. The presence of colloids in the blood helps to draw water into the circulation, increasing blood volume and improving tissue perfusion.

Pharmacodynamics

The pharmacodynamics of colloidal solutions are centered on their ability to exert osmotic pressure, which helps maintain blood volume and pressure. This effect is particularly important in conditions such as hypovolemia and shock, where fluid replacement is necessary to restore hemodynamic stability. The efficacy of colloidal solutions can vary depending on the type of colloid used, as well as the underlying clinical condition being treated.

Pharmacokinetics

Colloidal solutions are typically administered intravenously and their pharmacokinetics can vary based on the specific formulation. Generally, colloids are distributed throughout the vascular compartment and have a longer duration of action compared to crystalloids, as they remain in circulation longer. The elimination of colloids is primarily through the reticuloendothelial system, where they are metabolized or eliminated by the liver and spleen. Factors such as particle size and composition can influence their distribution and clearance.

Adverse effects

• Allergic reactions
• Injection site reactions
• Nausea
• Vomiting
• Headache
• Fever

Precautions

• Use with caution in patients with known allergies to any component of the formulation
• Monitor for signs of hypersensitivity during administration
• Consider volume overload in patients with cardiac or renal impairment

Pregnancy

The safety of colloidal solutions during pregnancy has not been established. Use only if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

It is not known whether colloidal solutions are excreted in human milk. Caution should be exercised when administering to breastfeeding mothers.

Storage

Store at room temperature, protect from light, and do not freeze. Keep out of reach of children.

Formulations

• Colloidal silver
• Colloidal gold
• Colloidal iron
• Other metal colloids

Indications

• Allergic rhinitis
• Common cold
• Sinusitis
• Seasonal allergies
• Nasal congestion

Dosage

Children: Refer to specific product formulations and BNF for Children for appropriate dosing in children, as it varies based on age and weight.

Adults: Refer to specific product formulations for dosing instructions, as they can vary by manufacturer and formulation.

Mechanism of action

The antihistamine component works by blocking histamine H1 receptors, which helps alleviate allergy symptoms such as sneezing, itching, and runny nose. The decongestant acts on adrenergic receptors in the nasal mucosa, causing vasoconstriction and reducing nasal congestion. Analgesic components help relieve pain by inhibiting the synthesis of prostaglandins in the central nervous system.

Pharmacodynamics

The combination of antihistamine and decongestant provides a synergistic effect, offering relief from multiple symptoms associated with colds and allergies. The antihistamine reduces allergic reactions and their symptoms, while the decongestant improves airflow through the nasal passages. The analgesic component alleviates discomfort, enhancing the overall therapeutic effect of the drug.

Pharmacokinetics

Absorption rates can vary based on the specific formulations of the drug. Typically, antihistamines are well absorbed from the gastrointestinal tract, with peak plasma concentrations occurring within 1 to 3 hours. Decongestants may have variable bioavailability depending on the route of administration. Metabolism mainly occurs in the liver, and elimination half-lives can range from a few hours to several hours depending on the specific agents included. Renal excretion plays a significant role in the clearance of these drugs.

Pregnancy

Safety in pregnancy has not been established. Use only if clearly needed and the benefits outweigh the risks.

Breast-feeding

Data is limited; use caution and consider the potential risks versus benefits.

Storage

Store at room temperature, away from moisture and heat. Keep out of reach of children.

Indications

• Monitoring respiratory function
• Assessment of metabolic status
• Management of respiratory acidosis
• Management of respiratory alkalosis

Dosage

Children: Dosing for interventions related to carbon dioxide levels in pediatric patients should be guided by clinical protocols and the BNF for Children.

Adults: Dosing for interventions related to carbon dioxide levels is typically based on clinical assessment and individual patient needs. Refer to clinical guidelines for specific scenarios.

Mechanism of action

Carbon dioxide acts primarily as a signaling molecule in the body, influencing respiratory drive and blood pH. It is produced during cellular respiration and is a critical component of the bicarbonate buffering system, which helps maintain acid-base homeostasis. Elevated levels of CO2 in the blood stimulate ventilation in the lungs, increasing the rate of gas exchange and facilitating the removal of excess CO2.

Pharmacodynamics

The pharmacodynamic effects of dioxides, particularly carbon dioxide, are closely related to its concentration in the blood. As CO2 levels increase, it leads to respiratory acidosis, which can stimulate the respiratory centers in the brain to increase ventilation. Conversely, low levels of CO2 can cause respiratory alkalosis, potentially leading to decreased respiratory drive. CO2 also plays a role in vasodilation and can affect blood flow and pressure through its influence on smooth muscle tone.

Pharmacokinetics

Carbon dioxide is produced endogenously during metabolic processes and is transported in the bloodstream primarily in three forms: dissolved in plasma, as bicarbonate ions (HCO3-), and bound to hemoglobin. The half-life of CO2 in the bloodstream is very short due to its rapid exchange with alveolar gas in the lungs. The elimination of CO2 occurs through exhalation, making it a dynamic component of respiratory physiology.

Pregnancy

Data on the effects of dioxide during pregnancy are limited. Caution is advised due to potential risks associated with exposure.

Breast-feeding

Limited data are available regarding the excretion of dioxide in human milk. Caution is recommended.

Storage

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

Dosage

Children: Refer to specific clinical guidelines for dosing in children, as no standard paediatric dosage is specified in the provided resources.

Adults: Refer to specific clinical guidelines for dosing, as no standard adult dosage is specified in the provided resources.

Mechanism of action

Ethylene glycol toxicity results from its metabolism to glycolic acid and other toxic metabolites. Glycolate accumulates in the body and is eliminated more slowly than ethylene glycol itself. The renal excretion of both compounds plays a crucial role in their elimination, accounting for a significant portion of the administered dose.

Pharmacodynamics

The pharmacodynamics of glycolate are closely tied to its role as a metabolite of ethylene glycol. Its accumulation can lead to metabolic acidosis, although minimal clinical effects have been observed at low doses. The relationship between glycolate and ethylene glycol indicates that glycolate may contribute to the overall toxic effects of ethylene glycol ingestion.

Pharmacokinetics

The pharmacokinetics of glycolate indicate that it reaches peak plasma levels between 4-6 hours after the administration of ethylene glycol. The elimination half-life of ethylene glycol is approximately 1.7 hours in rats and 3.4 hours in dogs. Glycolate is predominantly eliminated through renal excretion, with about 5% of the dose being excreted unchanged.

Pregnancy

There is limited data on the safety of glycolate in pregnancy. Caution is advised.

Breast-feeding

Data on the excretion of glycolate in human milk is not available. Caution is advised.

Storage

Store at room temperature, away from light and moisture.

Indications

• Cleansing agent in topical formulations
• Emulsifying agent in cosmetic products
• Foaming agent in shampoos and body washes

Dosage

Children: Refer to specific product formulations for appropriate concentrations and application methods.

Adults: Refer to specific product formulations for appropriate concentrations and application methods.

Mechanism of action

Lauryl sulfate functions as an anionic surfactant. It reduces the surface tension between different substances, allowing for better spreading and wetting. In the context of cleansing, it facilitates the removal of dirt and oils from the skin and hair by emulsifying these substances, thus making them easier to rinse away with water.

Pharmacodynamics

As a surfactant, lauryl sulfate displays properties that can disrupt cellular membranes and alter permeability. This mechanism is beneficial in enhancing the penetration of other therapeutic agents in topical formulations. However, its irritant potential on skin and mucous membranes should be noted, as it can lead to dryness and irritation with prolonged exposure.

Pharmacokinetics

Lauryl sulfate is primarily applied topically and is not intended for systemic absorption. When used in formulations, it acts locally at the site of application. Its absorption through the skin is minimal, and any systemic exposure is limited. Metabolism and excretion pathways are not well-defined for topical applications, as it is largely washed away after use.

Pregnancy

Safety during pregnancy has not been established. Use only if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

Unknown whether lauryl is excreted in human milk. Caution should be exercised when administering to nursing mothers.

Storage

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

Indications

• Used as an excipient in tablet formulations
• Used as a bulking agent in capsule formulations
• Used in food products as a thickener or stabilizer

Dosage

Children: Refer to specific product guidelines as dosage will depend on the formulation and the active ingredients.

Adults: Refer to specific product guidelines as dosage will depend on the formulation and the active ingredients.

Mechanism of action

Microcrystalline cellulose acts as a non-digestible filler that enhances the flow properties of powders during the manufacturing of tablets and capsules. It does not have a direct pharmacological action on the body but ensures that the active ingredients are effectively delivered to the patient.

Pharmacodynamics

As a non-active ingredient, microcrystalline cellulose does not exert pharmacodynamic effects typical of active pharmaceutical ingredients. Its primary role is to provide a stable and consistent matrix for the drug, facilitating the release of the active compound once ingested.

Pharmacokinetics

Microcrystalline cellulose is not absorbed in the gastrointestinal tract; it passes through the digestive system largely unchanged. It adds bulk to the stool, which may aid in promoting regular bowel movements. The substance is excreted in feces, where it contributes to dietary fiber intake.

Pregnancy

Data regarding the use of microcrystalline cellulose during pregnancy is limited. It is advisable to consult with healthcare professionals before use.

Breast-feeding

Microcrystalline cellulose is considered safe during breastfeeding, as it is not absorbed systemically.

Storage

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

Indications

• Used as a binder in tablet formulations
• Serves as a disintegrant to enhance drug release
• Utilized in the formulation of granules and powders

Dosage

Children: Refer to specific formulation guidelines as doses vary based on the formulation and active ingredients.

Adults: Refer to specific formulation guidelines as doses vary based on the formulation and active ingredients.

Mechanism of action

Pregelatinized starch acts primarily as a binder and disintegrant in tablet formulations. When exposed to moisture, it swells and rapidly absorbs water, leading to the disintegration of the tablet and facilitating the release of the active pharmaceutical ingredients.

Pharmacodynamics

The pharmacodynamic properties of pregelatinized starch are closely related to its physicochemical characteristics. It enhances the dissolution rate of poorly soluble drugs and helps in achieving a uniform distribution of the active ingredients within a formulation. Its ability to form a gel-like consistency in the presence of water aids in the controlled release of the drug.

Pharmacokinetics

As an excipient, pregelatinized starch is not intended to exert pharmacological effects on its own. It is generally regarded as safe and is not absorbed systemically. Its role is primarily mechanical, aiding in the formulation process of pharmaceutical products. The pharmacokinetics of any drug formulated with pregelatinized starch will depend on the active ingredients present in the formulation.

Pregnancy

Pregelatinized starch is generally considered safe for use during pregnancy as it is a food grade ingredient, but it is advisable to consult with a healthcare professional.

Breast-feeding

Pregelatinized starch is also considered safe during breastfeeding as it is unlikely to affect milk production or quality.

Storage

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

Formulations

• Powder
• Granules

Indications

• Potential role in bone health
• Support for connective tissue formation
• May aid in mineral metabolism

Dosage

Children: There is no established clinical dosage for silicon in paediatric populations, as it is not classified as an essential nutrient.

Adults: There is no established clinical dosage for silicon in adults, as it is not classified as an essential nutrient.

Mechanism of action

Silicon is believed to enhance the synthesis of glycosaminoglycans and collagen, which are important for the structural integrity of connective tissues. It may also influence the activity of certain enzymes involved in bone mineralization, thus playing a role in maintaining bone density and health.

Pharmacodynamics

The pharmacodynamics of silicon is not fully elucidated; however, it is thought to involve the modulation of bone metabolism and the promotion of connective tissue health. Silicon may have a synergistic effect with other minerals, such as calcium and magnesium, aiding in their utilization and metabolism in the body.

Pharmacokinetics

The pharmacokinetics of silicon is complex, as it is not absorbed through typical gastrointestinal pathways. Instead, silicon is thought to be taken up in the form of silicates and then distributed throughout the body, particularly in connective tissues. The elimination of silicon occurs primarily through renal excretion, with some variations depending on dietary intake and individual metabolism.

Pregnancy

Silicon is generally considered safe during pregnancy, as it is a naturally occurring element in the human body. However, specific recommendations regarding supplementation should be followed based on the advice of a healthcare provider.

Breast-feeding

Silicon is present in breast milk in small amounts. Its safety during breastfeeding is generally regarded as acceptable, although supplementation should be approached with caution and under medical advice.

Storage

Silicon should be stored in a cool, dry place, protected from light and moisture. Follow specific storage recommendations provided by the manufacturer if available.

Indications

• Nutritional supplementation
• Energy source in enteral nutrition
• Excipient in pharmaceutical formulations

Dosage

Children: Refer to specific guidelines or product inserts for dosing information, as it can vary based on the context of use.

Adults: Refer to specific guidelines or product inserts for dosing information, as it can vary based on the context of use.

Mechanism of action

Starch is broken down into glucose units by enzymes such as amylase during digestion. The glucose is then absorbed in the intestines and utilized for energy production in the body's cells. This pathway involves hydrolysis of the glycosidic bonds, converting starch into simpler sugars.

Pharmacodynamics

Starch primarily serves as an energy source. Its digestion and absorption lead to an increase in blood glucose levels, which provides energy for metabolic processes. In this context, it plays a crucial role in maintaining energy homeostasis in the body.

Pharmacokinetics

Starch is not absorbed in its polymeric form; it must first be enzymatically hydrolyzed into simpler sugars such as maltose and glucose. The digestion and absorption of starch occur predominantly in the small intestine, with glucose being readily absorbed into the bloodstream. The rate of absorption can vary depending on the type of starch and its physical form.

Adverse effects

• Allergic reactions
• Gastrointestinal discomfort
• Diarrhea
• Constipation

Precautions

• Use with caution in individuals with known allergies to starch or starch derivatives
• Monitor for gastrointestinal symptoms in patients with a history of digestive disorders

Pregnancy

Starch is generally considered safe for use during pregnancy. However, it should be consumed in moderation as part of a balanced diet.

Breast-feeding

Starch is deemed safe for nursing mothers when used in moderation as part of a balanced diet.

Storage

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

Formulations

• Powder
• Granules
• Tablets
• Suspensions

Mechanism of action

Allopurinol is a structural analog of the natural purine base, hypoxanthine. After ingestion, allopurinol is metabolized to its active metabolite, oxypurinol (_alloxanthine_) in the liver, which acts as an inhibitor of xanthine oxidase enzyme. Allopurinol and its active metabolite inhibit xanthine oxidase, the enzyme that converts hypoxanthine to xanthine and xanthine to uric acid. Inhibition of this enzyme is responsible for the effects of allopurinol. This drug increases the reutilization of hypoxanthine and xanthine for nucleotide and nucleic acid synthesis by a process that involves the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRTase). This process results in an increased nucleotide concentration, which causes feedback inhibition of de novo purine synthesis. The end result is decreased urine and serum uric acid concentrations, which decreases the incidence of gout symptoms. Accompanying the reduction of serum uric acid by allopurinol is an increase in the serum and urine concentrations of hypoxanthine and xanthine (due to inhibition of xanthine oxidase). In the absence of allopurinol, regular urinary excretion of oxypurines almost entirely occurs in the form of uric acid. After the ingestion of allopurinol, the contents of excreted urine are hypoxanthine, xanthine, and uric acid. Because each substance has its own individual solubility, the concentration of uric acid in plasma is decreased without exposing the renal tissues to a high load of uric acid, thereby decreasing the risk of crystalluria. By lowering the uric acid concentration in the plasma below its limits of solubility, allopurinol encourages the dissolution of gout tophi. Although the levels of hypoxanthine and xanthine are found to be increased after allopurinol ingestion, the risk of deposition in renal tissues is less than that of uric acid, as they become more soluble and are rapidly excreted by the kidney. Allopurinol inhibits xanthine oxidase, the enzyme that catalyzes the conversion of hypoxanthine to xanthine and of xanthine to uric acid. Oxypurinol, a metabolite of allopurinol, also inhibits xanthine oxidase. By inhibiting xanthine oxidase, allopurinol and its metabolite block conversion of the oxypurines (hypoxanthine and xanthine) to uric acid, thus decreasing serum and urine concentrations of uric acid. The drug differs, therefore, from uricosuric agents which lower serum urate concentrations by promoting urinary excretion of uric acid. Xanthine oxidase concentrations are not altered by long-term administration of the drug. Allopurinol does not directly interfere with purine nucleotide or nucleic acid synthesis. The drug, however, indirectly increases oxypurine and allopurinol ribonucleotide concentrations and decreases phosphoribosylpyrophosphate concentrations, thus decreasing de novo purine biosynthesis by pseudofeedback inhibition. In addition, allopurinol increases the incorporation of hypoxanthine and xanthine into DNA and RNA, thereby further decreasing serum urate concentrations. Allopurinol may produce a deficit of total purines (uric acid and oxypurines) amounting to several hundred mg daily. Accompanying the decrease in uric acid produced by allopurinol is an increase in serum and urine concentrations of hypoxanthine and xanthine. Plasma concentrations of these oxypurines do not, however, rise commensurately with the fall in serum urate concentrations and are often 20-30% less than would be expected in view of urate concentrations prior to allopurinol therapy. This discrepancy occurs because renal clearance of the oxypurines is at least 10 times greater than that of uric acid. In addition, normal urinary purine output is almost exclusively uric acid, but after treatment with allopurinol, it is composed of uric acid, xanthine, and hypoxanthine, each having independent solubility. Thus, the risk of crystalluria is reduced. Alkalinization of the urine increases the solubility of the purines, further minimizing the risk

Pharmacodynamics

Allopurinol decreases the production of uric acid by stopping the biochemical reactions that precede its formation. This process decreases urate and relieves the symptoms of gout, which may include painful tophi, joint pain, inflammation, redness, decreased range of motion, and swelling.

Mechanism of action

Ethylene glycol toxicity results from its metabolism to glycolic acid and other toxic metabolites. The accumulation of glycolate and the elimination kinetics of ethylene glycol and its metabolites are not well understood, so studies with male Sprague-Dawley rats and mixed breed dogs have been carried out. Ethylene glycol was administered by gavage to rats and dogs which were placed in metabolic cages for urine and blood sample collection at timed intervals. The peak plasma level of ethylene glycol occurred at 2 hr after dosing and that of glycolate between 4-6 hr. The rate of ethylene glycol elimination was somewhat faster in rats with a half-life of 1.7 hr compared to 3.4 hr in dogs. The maximum plasma level of glycolate was greater in rats although the pattern of accumulation was similar to that in dogs. Glycolate disappeared from the plasma at the same time as ethylene glycol, suggesting a slower rate of elimination of the metabolite than that of ethylene glycol. Renal excretion of ethylene glycol was an important route for its elimination accounting for 20-30% of the dose. Renal excretion of glycolate represented about 5% of the dose. Ethylene glycol induced an immediate, but short lived diuresis compared to that in control rats. Minimal clinical effects (mild acidosis with no sedation) were noted at these doses of ethylene glycol (1-2 g/kg) in both rats and dogs. The results indicate that the toxicokinetics of ethylene glycol and glycolate were similar in both species. The effect of 0.35 to 0.8 mmol/kg glycolic acid and 1.0 to 4.4 mmol/kg sodium glycolate on cyclopropane-epinephrine induced cardiac arrhythmias was examined using dogs. Doses of 0.35 to 0.5 mmol/kg glycolic acid increased the duration of arrhythmias in the 13 dogs tested, whereas doses >0.5 mmol/kg decreased or totally eliminated the arrhythmias in each of 11 dogs. Depression was observed for many of the dogs at higher doses. Sodium glycolate was much less effective in decreasing the arrhythmias, with 3 mmol/kg being required and its action being transient.