DREZ OINTMENT

Indications

• Amebiasis
• Trichomoniasis
• Giardiasis
• Anaerobic bacterial infections
• Bacterial vaginosis
• Clostridium difficile infection

Dosage

Children: For children aged 1 month to 11 years, 7.5 mg/kg every 8 hours for 7 days (maximum dose 400 mg). For children aged 12-17 years, 400 mg every 8 hours for 7 days.

Adults: 1 g three times a day for 3 days, then 1 g twice daily for a total treatment duration of 7 days. In cases of Clostridium difficile infection, treatment may extend to 10 days.

Mechanism of action

The exact mechanism of action of metronidazole is not fully established. However, it is believed that anaerobic bacteria and protozoa reduce metronidazole to reactive intermediates that bind to DNA and inhibit nucleic acid synthesis, leading to cell death. Metronidazole is selectively activated in anaerobic conditions, making it effective against obligate anaerobes.

Pharmacodynamics

Metronidazole exhibits both antibacterial and antiprotozoal activities, effectively treating infections caused by anaerobic bacteria. It demonstrates significant antibacterial activity against most obligate anaerobes but is less effective against facultative anaerobes and obligate aerobes. The drug's cytotoxic effects result from DNA strand damage in susceptible microorganisms, which can lead to cell death. Caution is advised due to the potential for peripheral neuropathy and convulsions, especially at higher doses.

Pharmacokinetics

Metronidazole is well absorbed following oral administration and is distributed widely throughout the body, including the central nervous system. It undergoes hepatic metabolism, primarily through oxidation and conjugation, and is excreted mainly in urine. The pharmacokinetic profile may vary in patients with hepatic impairment, and dosage adjustments may be necessary.

Adverse effects

• Peripheral neuropathy
• Convulsions
• Nausea
• Vomiting
• Diarrhea
• Headache
• Dizziness
• Abdominal cramps
• Metallic taste
• Skin rash

Interactions

• Metronidazole + Coumarins: Increases anticoagulant effect
• Metronidazole + Lithium: Increases concentration
• Metronidazole + Busulfan: Increases risk of toxicity (unknown)
• Metronidazole + Capecitabine: Increases risk of capecitabine toxicity (unknown)
• Metronidazole + Fluorouracil: Increases risk of toxicity (unknown)
• Metronidazole + Alkylating agents: Increases risk of toxicity (unknown)

Precautions

• Caution in patients with history of neurological disorders
• Monitor for signs of peripheral neuropathy
• Use with caution in patients with hepatic impairment
• Avoid excessive alcohol consumption during treatment

Pregnancy

No information available; manufacturer advises avoidance unless essential.

Breast-feeding

Amount in milk probably too small to be harmful.

Storage

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

Formulations

• Metronidazole 0.75% gel
• Metronidazole 0.75% cream
• Metronidazole powder and solvent for nebuliser solution
• Metronidazole injection
• Metronidazole oral tablets (various strengths)

Indications

• Computed tomography (CT) imaging
• Angiography
• Fluoroscopy
• Intravenous urograms
• Cholangiography

Dosage

Children: Paediatric dosing depends on the child's age, weight, and the specific procedure being performed. Consult the BNF for Children for appropriate dosing recommendations.

Adults: Dosage varies based on the specific iodinated contrast agent used and the type of procedure. Refer to specific product guidelines for detailed dosing information.

Mechanism of action

Iodinated contrast agents work by increasing the absorption of X-rays, due to the high atomic number of iodine, which is significantly greater than that of soft tissues. When introduced into the body, these agents help to delineate vascular structures and organs, allowing for improved visualization in imaging studies.

Pharmacodynamics

The pharmacodynamics of iodinated contrast agents are characterized by their ability to alter the radiographic density of tissues. They enhance the contrast between different tissues, especially in vascular structures, by providing a stark difference in X-ray attenuation. The pharmacological effects are largely dose-dependent, influencing the quality of imaging results and the safety profile in patients.

Pharmacokinetics

Iodinated contrast agents are typically administered intravenously. Their distribution in the body is rapid, with peak plasma concentrations occurring soon after administration. The agents are primarily eliminated through renal excretion, with a significant portion excreted unchanged in urine within 24 hours. The half-life can vary depending on the specific agent used and the patient's renal function.

Adverse effects

• Hypersensitivity reactions
• Nausea
• Vomiting
• Thyroid dysfunction
• Nephrotoxicity
• Extravasation injury

Interactions

• May interact with anticoagulants, increasing the risk of bleeding
• May affect thyroid function tests
• Concurrent use with nephrotoxic agents may increase risk of renal impairment

Precautions

• Use with caution in patients with a history of thyroid disease
• Monitor renal function prior to administration, especially in patients with pre-existing renal impairment
• Ensure adequate hydration to reduce the risk of nephrotoxicity

Pregnancy

Iodinated contrast agents should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. They should be avoided in the first trimester if possible.

Breast-feeding

Iodinated contrast agents are generally considered safe for use during breastfeeding, but mothers should be advised to monitor their infants for any signs of adverse reactions.

Storage

Store at room temperature, protect from light, and keep away from moisture. Check expiry date before use.

Formulations

• Iodinated contrast medium for intravenous use
• Iodinated contrast medium for intra-arterial use
• Iodinated contrast medium for oral administration

Indications

• Topical antiseptic for skin disinfection
• Preparation of skin prior to surgery
• Infection prevention in wound care
• Treatment of minor cuts and abrasions
• Oral rinse for dental antisepsis

Dosage

Children: Refer to specific product monographs or guidelines for paediatric dosing, as this can vary based on formulation and indication. Typically used topically; follow manufacturer's instructions.

Adults: Refer to specific product monographs or guidelines for adult dosing, as this can vary based on formulation and indication. Typically used topically; follow manufacturer's instructions.

Mechanism of action

Povidone's mechanism of action as an antiseptic primarily involves the release of iodine, which penetrates microbial cell walls and disrupts nucleic acid and protein synthesis. This leads to cell death and inhibition of microbial growth. The polymer itself also adsorbs to surfaces, providing a sustained antimicrobial effect.

Pharmacodynamics

Povidone exhibits broad-spectrum antimicrobial activity due to its ability to release iodine. The effectiveness of povidone-iodine is influenced by factors such as concentration, contact time, and the presence of organic matter. Its action is rapid, and it remains effective in the presence of blood and other body fluids, making it suitable for surgical and wound care applications.

Pharmacokinetics

Povidone is primarily administered topically, and its absorption through intact skin is minimal. When used as an antiseptic, it acts locally at the site of application. In cases where high concentrations are used, systemic absorption may occur, but it is generally considered low. The elimination half-life of iodine from the body is approximately 1-2 days, with renal excretion playing a significant role in the elimination of iodine.

Adverse effects

• Skin irritation
• Allergic reactions
• Staining of skin or mucous membranes
• Hypersensitivity reactions

Precautions

• Use with caution in patients with known allergies to iodine or iodine-containing products
• Avoid contact with eyes
• Not for use in deep puncture wounds or serious burns

Pregnancy

Considered safe for topical use during pregnancy, but consult with a healthcare provider before use.

Breast-feeding

Topical use is generally considered safe during breastfeeding; however, consult a healthcare provider.

Storage

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

Formulations

• Topical solution
• Ointment
• Swab sticks

Mechanism of action

The exact mechanism of action of metronidazole has not been fully established, however, it is possible that an intermediate in the reduction of metronidazole which is only made by anaerobic bacteria and protozoa, binds deoxyribonucleic acid and electron-transport proteins of organisms, blocking nucleic acid synthesis. After administration, metronidazole enters cells by passive diffusion. Following this, ferredoxin or flavodoxin reduce its nitro group to nitro radicals. The redox potential of the electron transport portions of anaerobic or microaerophilic microorganisms renders metronidazole selective to these organisms, which cause nitro group reduction, leading to the production of toxic metabolites. These include N-(2-hydroxyethyl) oxamic acid and acetamide, which may damage DNA of replicating organisms. Microbicidal; active against most obligate anaerobic bacteria and protozoa by undergoing intracellular chemical reduction via mechanisms unique to anaerobic metabolism. Reduced metronidazole, which is cytotoxic but short-lived, interacts with DNA to cause loss of helical structure, strand breakage, and resultant inhibition of nucleic acid synthesis and cell death. Metronidazole is bactericidal, amebicidal, and trichomonacidal in action. The exact mechanism of action of the drug has not been fully elucidated. Metronidazole is un-ionized at physiologic pH and is readily taken up by anaerobic organisms or cells. In susceptible organisms or cells, metronidazole is reduced by low-redox-potential electron transport proteins (e.g., nitroreductases such as ferredoxin) to unidentified polar product(s) which lack the nitro group. The reduction product(s) appears to be responsible for the cytotoxic and antimicrobial effects of the drug which include disruption of DNA and inhibition of nucleic acid synthesis. Metronidazole is equally effective against dividing and nondividing cells. In in vivo studies in rats given metronidazole in dosages of 2-4 mg/100 g of body weight, the drug reportedly inhibited the development of formalin-induced edema in the rat paw. In vitro in neutrophils, metronidazole has a dose-dependent inhibitory effect on generation of hydrogen peroxide and hydroxyl radicals, oxidants that may cause tissue injury at the site of inflammation. This antioxidant effect appears to be caused by a direct effect on neutrophil function and may contribute to the drug's anti-inflammatory effect in vivo. Results of in vitro studies using leukocytes obtained from patients with Crohn's disease indicate that exposing the cells to metronidazole concentrations of 10 or 50 mcg/mL improved both spontaneous and induced leukocyte migration in cells that previously exhibited reduced migration; the drug had no effect on leukocytes obtained from healthy adults or patients with Crohn's disease when the cells exhibited normal migration prior to exposure to the drug. This effect on leukocyte migration also was observed in vivo in adults with Crohn's disease who received a single 400-mg dose of metronidazole. It has been suggested that metronidazole may increase leukocyte migration by a direct effect on the leukocytes, possibly by causing the release of surface-bound immune complexes from the cell surface.

Pharmacodynamics

Metronidazole treats amebiasis, trichomoniasis, and giardiasis, exerting both antibacterial and antiprotozoal activities. Metronidazole is an effective treatment for some anaerobic bacterial infections. Metronidazole has shown antibacterial activity against the majority of obligate anaerobes, however, during in vitro studies, it does not demonstrate significant action against facultative anaerobes or obligate aerobes. The nitro group reduction of metronidazole by anaerobic organisms is likely responsible for the drug's antimicrobial cytotoxic effects, causing DNA strand damage to microbes. A note on convulsions and neuropathy and carcinogenesis It is important to be aware of the risk of peripheral neuropathy and convulsions associated with metronidazole, especially at higher doses. If convulsions or numbness of an extremity occur, discontinue the drug immediately. Metronidazole has been found to be carcinogenic in mice and rats. The relevance to this effect in humans is unknown. It is advisable to only administer metronidazole when clinically necessary and only for its approved indications.