Nitrofurantoin

Indications

• Urinary tract infections (uncomplicated)
• Urinary tract infection prophylaxis
• Recurrent urinary tract infections

Dosage

Children: Child 3 months–11 years: 750 micrograms/kg 4 times a day for 3 days. Child 12–15 years: 50 mg 4 times a day for 3 days (7 days in pregnant women). Child 16–17 years: 50 mg 4 times a day for 3 days (7 days in males and pregnant women).

Adults: Adult: 50 mg 4 times a day for 3 days (7 days in males and pregnant women).

Mechanism of action

Nitrofurantoin is converted by bacterial nitroreductases to electrophilic intermediates that inhibit the citric acid cycle, as well as the synthesis of DNA, RNA, and proteins in bacteria. This mechanism disrupts vital processes necessary for bacterial survival and reproduction, leading to their death.

Pharmacodynamics

Nitrofurantoin exerts its antibacterial effects by interfering with multiple biological pathways in bacteria, ultimately leading to bacterial cell death. It achieves therapeutic concentrations quickly in the urine, which is essential for its efficacy in treating urinary infections. However, its rapid clearance from the body requires frequent dosing to maintain effective levels.

Pharmacokinetics

Nitrofurantoin is rapidly absorbed from the gastrointestinal tract and reaches peak plasma concentrations within 1 to 3 hours after oral administration. It is primarily excreted through the kidneys, with a significant portion being eliminated unchanged in the urine. The drug has a short half-life, which necessitates multiple doses throughout the day to maintain adequate therapeutic levels.

Contra-indications

• Gout
• Metabolic acidosis
• Severe dehydration
• Hepatic impairment
• Renal impairment (eGFR less than 10 mL/minute/1.73 m2)

Adverse effects

• Epigastric discomfort
• Skin reactions
• Agranulocytosis
• Alopecia
• Anaemia
• Angioedema
• Aplastic anaemia
• Appetite decreased
• Arthralgia
• Asthenia
• Chest pain
• Chills
• Circulatory collapse
• Confusion
• Cough
• Cyanosis
• Depression
• Diarrhoea
• Dizziness
• Drowsiness
• Dyspnoea
• Eosinophilia
• Euphoric mood
• Fever
• Granulocytopenia
• Haemolytic anaemia
• Headache
• Hepatic disorders
• Intracranial hypertension
• Increased risk of infection
• Leukopenia
• Lupus-like syndrome
• Nausea
• Nystagmus
• Pancreatitis
• Psychotic disorder
• Pulmonary reactions
• Respiratory disorders
• Skin reactions

Interactions

• Moderate interaction with topical prilocaine (increases risk of methaemoglobinaemia)
• Moderate interaction with topical anaesthetics (increases risk of methaemoglobinaemia)
• Moderate interaction with prilocaine (increases risk of methaemoglobinaemia)
• Unknown interaction with dapsone (increases risk of methaemoglobinaemia)

Precautions

• Avoid in patients with hepatic impairment
• Avoid in patients with renal impairment (eGFR less than 10 mL/minute/1.73 m2)
• Consider potential for false laboratory test results for urinary sepsis

Pregnancy

There is inadequate evidence of safety, but it has been in wide use for many years without apparent ill consequence, however, the

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

• Calcium deficiency
• Osteoporosis prevention
• Osteomalacia
• Rickets
• Dietary supplementation in individuals with increased calcium and phosphorus requirements

Dosage

Children: Refer to established guidelines for specific dosing based on clinical indications and individual patient needs.

Adults: Refer to established guidelines for specific dosing based on clinical indications and individual patient needs.

Mechanism of action

Dicalcium phosphate dissociates in the gastrointestinal tract to release calcium and phosphate ions. Calcium plays a vital role in various physiological processes, including muscle contraction, neurotransmitter release, and blood coagulation. The phosphate ions are essential for energy metabolism and are integral to the formation of ATP (adenosine triphosphate), nucleic acids, and cellular membranes. The availability of these ions supports bone mineralization and overall skeletal integrity.

Pharmacodynamics

The pharmacodynamics of dicalcium phosphate involves its role in maintaining calcium and phosphate homeostasis in the body. Adequate levels of calcium are critical for normal bone metabolism, while phosphate is necessary for the formation of hydroxyapatite in bone tissue. The balance of these minerals is regulated by hormones such as parathyroid hormone and calcitriol, which modulate their absorption in the intestines and reabsorption in the kidneys. Supplementation with dicalcium phosphate can help alleviate deficiencies and support bone health.

Pharmacokinetics

Dicalcium phosphate is absorbed in the gastrointestinal tract, with varying absorption rates depending on the presence of other dietary components. Calcium absorption occurs primarily in the small intestine, while phosphate absorption can occur throughout the gastrointestinal tract. After absorption, calcium is distributed to bones, teeth, and soft tissues, while excess calcium is excreted through urine. The pharmacokinetics may be influenced by factors such as age, dietary habits, and the presence of gastrointestinal disorders.

Adverse effects

• Gastrointestinal disturbances (nausea, constipation)
• Hypercalcemia
• Kidney stones
• Fatigue
• Muscle weakness

Interactions

• May interact with calcium channel blockers
• Increased risk of hypercalcemia with thiazide diuretics
• May affect the absorption of certain antibiotics (e.g., tetracyclines)

Precautions

• Use with caution in patients with renal impairment
• Monitor calcium levels in patients receiving high doses
• Consider potential interactions with other medications

Pregnancy

Dicalcium is generally considered safe in pregnancy when used as directed, but high doses should be avoided.

Breast-feeding

Calcium is an essential nutrient during breastfeeding, but excessive supplementation should be approached with caution.

Storage

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

Formulations

• Tablets
• Powders
• Chewable tablets

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.

Indications

• Lactose intolerance
• As a filler or excipient in pharmaceutical formulations

Dosage

Children: Refer to the BNF for Children for specific dosing information based on age and clinical context.

Adults: Refer to the BNF for specific dosing information based on clinical context.

Mechanism of action

Lactose is metabolized in the intestine by the enzyme lactase into its constituent monosaccharides, glucose and galactose. In individuals with lactase deficiency, unabsorbed lactose passes into the colon, where it is fermented by bacteria, leading to gas production and osmotic effects that contribute to diarrhea.

Pharmacodynamics

The pharmacodynamics of lactose are primarily related to its effects on gastrointestinal function. In healthy individuals, lactose is effectively broken down into glucose and galactose, which are absorbed and utilized for energy. In individuals with lactose intolerance, the unabsorbed lactose can cause osmotic diarrhea and colonic fermentation, leading to discomfort and symptoms associated with lactose intolerance.

Pharmacokinetics

Lactose is not absorbed in the gastrointestinal tract until it is hydrolyzed into glucose and galactose by lactase. The absorption of glucose and galactose occurs in the small intestine. The half-life is not applicable as lactose is not typically administered as a medication but is rather ingested as a natural component of food. Its metabolism primarily occurs in the intestine.

Adverse effects

• Bloating
• Diarrhea
• Abdominal pain
• Flatulence

Precautions

• Use with caution in patients with lactose intolerance.
• Consider potential for gastrointestinal upset in sensitive individuals.

Pregnancy

Lactose is generally considered safe for use during pregnancy. However, consult a healthcare professional for individual advice.

Breast-feeding

Lactose is safe to use while breastfeeding, as it is a natural sugar present in breast milk.

Storage

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

Formulations

• Powder
• Granules
• Tablets
• Syrup

Indications

• Nutritional support
• Source of carbohydrates
• Dietary fiber source
• Animal feed

Dosage

Children: As with adults, there are no specific dosing recommendations for maize for children. It can be introduced into the diet in age-appropriate forms and quantities, keeping in mind the overall dietary balance.

Adults: There are no specific dosing recommendations for maize as it is typically consumed as part of a balanced diet. It can be included in daily meals in various forms such as whole kernels, flour, or as part of dishes.

Mechanism of action

Maize primarily acts as a source of energy due to its high carbohydrate content. The complex carbohydrates in maize are broken down into glucose, which is then utilized by the body for energy production. It also contributes to dietary fiber intake, which can aid in digestive health and regulation of blood sugar levels.

Pharmacodynamics

The consumption of maize influences blood glucose and insulin levels due to its carbohydrate content. It has a relatively low glycemic index when consumed in whole form, which can help in managing blood sugar levels. The dietary fiber present in maize can also promote satiety and aid in weight management.

Pharmacokinetics

The digestion of maize begins in the mouth with salivary amylase breaking down starches into simpler sugars. In the stomach and small intestine, enzymes further break down these carbohydrates. The resultant glucose is absorbed into the bloodstream, where it is transported to cells for energy production. The absorption rate can vary based on the form of maize consumed (e.g., whole kernels versus processed forms).

Pregnancy

Maize is generally considered safe for consumption during pregnancy as it is a staple food and provides essential nutrients.

Breast-feeding

Maize is safe to consume while breastfeeding and can provide important nutrients to both the mother and the infant.

Storage

Store in a cool, dry place, away from moisture and pests. Properly sealed containers can help prolong shelf life.

Formulations

• Whole maize grains
• Maize flour (cornmeal)
• Maize starch
• Maize oil

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

• Topical antiseptic for skin disinfection
• Surgical scrubs and hand sanitizers
• Wound care management
• Pharmaceutical excipient in solid and liquid formulations

Dosage

Children: Refer to specific product guidelines for pediatric dosing recommendations, as doses can vary based on formulation and intended use.

Adults: Refer to specific product guidelines for dosing recommendations, as doses can vary based on the formulation and intended use.

Mechanism of action

Povidone acts by forming a complex with iodine when used as an antiseptic, which releases iodine slowly to exert its antimicrobial effect. The iodine disrupts microbial cell walls and interferes with protein synthesis, leading to cell death. Additionally, as a polymer, povidone can enhance drug solubility and stability by forming a hydrophilic matrix.

Pharmacodynamics

Povidone has a broad spectrum of antimicrobial activity against bacteria, viruses, and fungi. Its antiseptic properties are primarily due to the release of iodine, which is effective in reducing microbial load and preventing infection. The polymer's ability to bind to various substances allows it to be utilized in formulations that require improved stability and solubility.

Pharmacokinetics

Povidone is not absorbed systemically when applied topically, as it remains localized at the site of application. Its pharmacokinetics are largely dependent on the formulation and route of administration, with the polymer being metabolized by hydrolysis and excreted in urine as low-molecular-weight compounds. The release and activity of iodine are influenced by the concentration of povidone and the presence of organic matter.

Adverse effects

• Local irritation
• Allergic reactions
• Skin rashes
• Hypersensitivity reactions

Precautions

• Use with caution in patients with known allergies to iodine or povidone-iodine
• Avoid use in deep puncture wounds or serious burns

Pregnancy

Povidone is generally considered safe for use during pregnancy, but it is advisable to consult a healthcare professional before use.

Breast-feeding

Povidone is considered safe during breastfeeding, but it is recommended to consult a healthcare professional.

Storage

Store at room temperature, away from moisture and heat. Keep the container tightly closed.

Formulations

• Topical solution
• Ointment
• Surgical scrub
• Gauze impregnated with povidone-iodine

Indications

• Bone health
• Skin health
• Hair and nail strength
• Connective tissue support

Dosage

Children: Refer to specific product guidelines, as doses may vary based on formulation and intended use.

Adults: Refer to specific product guidelines, as doses may vary based on formulation and intended use.

Mechanism of action

Silicon is thought to influence collagen synthesis and stabilization, enhancing the structural integrity of connective tissues. It may also modulate the activity of enzymes related to the synthesis of glycosaminoglycans, which are vital for maintaining the structural framework of tissues.

Pharmacodynamics

Silicon compounds may exhibit antioxidant properties and are involved in the metabolism of calcium and other minerals, potentially aiding in bone mineralization. Additionally, silicon may enhance the mechanical properties of connective tissues, contributing to their resilience and flexibility.

Pharmacokinetics

Silicon is primarily absorbed in the gastrointestinal tract, with its bioavailability dependent on the form in which it is consumed. It is distributed throughout the body, particularly in connective tissues, and is excreted via the kidneys. The exact half-life of silicon in the body is not well established, but it is generally considered to be rapidly eliminated.

Pregnancy

Safety in pregnancy has not been established.

Breast-feeding

Safety during breastfeeding has not been established.

Storage

Store in a cool, dry place, away from light.

Indications

• Preservation of food products
• Preservation of pharmaceutical formulations
• Antimicrobial agent in cosmetic products

Dosage

Children: Refer to specific product guidelines for dosage as it varies by formulation and intended use.

Adults: Refer to specific product guidelines for dosage as it varies by formulation and intended use.

Mechanism of action

Sorbate acts primarily by inhibiting the growth of fungi and some bacteria. It interferes with the microbial cell membrane, disrupting its integrity and function, which leads to cell death. The presence of sorbate alters the pH and osmotic balance within the microbial cell, inhibiting key metabolic processes necessary for reproduction and survival.

Pharmacodynamics

Sorbate exhibits its antimicrobial effects at relatively low concentrations. It is most effective in acidic environments, typically at a pH of 4.5 or lower. The compound is more effective against yeasts and molds compared to bacteria. Its mode of action is primarily through the inhibition of fatty acid synthesis and alteration of membrane permeability in target microorganisms.

Pharmacokinetics

Sorbate is generally regarded as having low toxicity and is rapidly metabolized in the human body. It is absorbed in the gastrointestinal tract when ingested and is then distributed throughout the body. The compound undergoes conversion to various metabolites and is primarily excreted via the urine. Its half-life and specific metabolic pathways can vary depending on the form of administration and individual patient factors.

Pregnancy

There is limited data on the safety of sorbate in pregnancy. Use only if clearly needed and potential benefits justify the risks.

Breast-feeding

There is insufficient information regarding the excretion of sorbate in human milk. Caution is advised when administering to nursing mothers.

Storage

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

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

Indications

• Used as an excipient in drug formulations
• Pleurodesis for the management of recurrent pleural effusions

Dosage

Children: Refer to specific guidelines for paediatric use, as dosing may differ based on age and clinical condition.

Adults: Refer to specific guidelines for the appropriate dosage in pleurodesis and other applications, as it may vary based on clinical context.

Mechanism of action

Talc exhibits very good absorptive properties, allowing it to absorb moisture and other substances effectively. This characteristic is particularly useful in pharmaceutical formulations, where it may enhance the stability and texture of the drug product.

Pharmacodynamics

Talc's primary pharmacodynamic effect is its ability to act as an inert filler and bulking agent in pharmaceutical preparations. It does not have any intrinsic pharmacological activity but serves to improve the physical properties of formulations, such as flowability and compressibility.

Pharmacokinetics

Talc is not absorbed systemically when used as an excipient or in medical procedures. Its effects are local, and it remains in the site of application, where it functions primarily as a mechanical agent. The pharmacokinetics of talc in the context of its use in pleurodesis involves its ability to promote adhesion of the pleural surfaces, thereby preventing fluid accumulation.

Pregnancy

Talc is classified as a substance with minimal systemic absorption, but safety during pregnancy has not been well established. Consult relevant guidelines.

Breast-feeding

Talc is not expected to be absorbed in significant amounts; however, caution is advised and consult guidelines.

Storage

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

Mechanism of action

Nitrofurantoin is converted by bacterial nitroreductases to electrophilic intermediates which inhibit the citric acid cycle as well as synthesis of DNA, RNA, and protein. MICROSOMAL AND SOLUBLE FRACTIONS FROM BOTH RAT LIVER AND LUNG MEDIATED THE COVALENT BINDING OF (14)C-LABELED NITROFURANTOIN (I) TO TISSUE MACROMOLECULES IN VITRO. OXYGEN STRONGLY INHIBITED THE BINDING IN BOTH FRACTIONS, AND CARBON MONOXIDE FAILED TO INHIBIT THE BINDING IN MICROSOMAL PREPARATIONS, INDICATING ACTIVATION OF I IN BOTH SYSTEMS BY NITROREDUCTION RATHER THAN OXIDATION OF THE FURAN RING. MICROSOMAL NITROREDUCTION AND COVALENT BINDING OF I WERE INHIBITED BY AN ANTIBODY AGAINST NADPH-CYTOCHROME C REDUCTASE AND COVALENT BINDING WAS ENHANCED BY THE ADDITION OF FAD. IN SOLUBLE FRACTIONS, MAXIMUM RATES OF COVALENT BINDING WERE OBTAINED IN THE PRESENCE OF NADH AND HYPOXANTHINE, AND IT WAS INHIBITED BY ALLOPURINOL, A XANTHINE OXIDASE INHIBITOR. REDUCED GLUTATHIONE DECREASED COVALENT BINDING OF I IN BOTH MICROSOMAL AND SOLUBLE FRACTIONS OF LIVER AND LUNG, BUT THE RATE OF NITROREDUCTION WAS UNAFFECTED. THE HYPOTHESIS IS PRESENTED THAT THE TOXICITY OF NITROFURANS SUCH AS NITROFURANTOIN (I), WHICH ARE USED IN COMMERCIAL POULTRY PRODUCTION, IS DUE TO OXIDATIVE METABOLIC STRESS CAUSED BY THE O2- FREE RADICAL FORMED DURING METABOLISM OF THE COMPOUNDS.

Pharmacodynamics

Nitrofurantoin interferes with vital processes in bacteria, which leads to their death. Nitrofurantoin rapidly reaches therapeutic concentrations in the urine and is also cleared rapidly.

Mechanism of action

It has very good absorptive properties.