Usage
Miconazole is prescribed for the treatment of fungal infections, including:
- Cutaneous candidiasis: Yeast infections affecting the skin, such as groin, abdominal folds, intergluteal fold, under the breasts, and between toes or fingers.
- Candidal balanitis: Yeast infection of the penis.
- Dermatophyte infections: Fungal infections of the skin like ringworm (tinea corporis), jock itch (tinea cruris), and athlete’s foot (tinea pedis).
- Oropharyngeal candidiasis (Oral Thrush): Yeast infection of the mouth and throat.
- Vaginal candidiasis (Yeast Infection): Yeast infection of the vagina.
Pharmacological Classification: Antifungal (Imidazole class)
Mechanism of Action: Miconazole inhibits the synthesis of ergosterol, a crucial component of fungal cell membranes. This disruption leads to increased permeability of the fungal cell membrane, ultimately causing cell death.
Alternate Names
Miconazole Nitrate
Brand Names: Monistat, Micatin, Daktarin, Oravig, Lotrimin AF, and numerous others.
How It Works
Pharmacodynamics: Miconazole exerts its fungicidal effect (killing fungi) by inhibiting ergosterol biosynthesis. This disrupts the integrity of the fungal cell membrane, leading to cellular leakage and death. It also inhibits the biosynthesis of triglycerides and phospholipids by fungi and may inhibit oxidative and peroxidative enzyme activity, further contributing to its antifungal action.
Pharmacokinetics:
- Absorption: Topical miconazole is minimally absorbed through intact skin. Systemic absorption is slightly higher after intravaginal administration (1-2% bioavailability). Oral (buccal) absorption is low.
- Metabolism: Primarily hepatic, via CYP2C9 and CYP3A4 enzymes.
- Elimination: Mainly through feces with minimal renal excretion.
Mode of Action: Inhibits the fungal cytochrome P450 enzyme lanosterol 14α-demethylase, a key enzyme in ergosterol biosynthesis.
Receptor Binding/Enzyme Inhibition/Neurotransmitter Modulation: Miconazole primarily acts through the inhibition of the lanosterol 14α-demethylase enzyme. It is also a known inhibitor of CYP2C9 and 3A4 enzymes, which can lead to drug interactions.
Dosage
Standard Dosage
Adults:
- Topical: Apply to affected area twice daily.
- Vaginal: Varies depending on product and formulation (100 mg - 1200 mg suppository/cream). See specific product instructions.
- Buccal (Oravig): One 50 mg tablet placed on the upper gum once daily for 14 days.
Children:
- Topical: Apply to affected area twice daily.
- Oral Gel: Infants (4-24 months): 1.25 mL four times daily after meals. Children (2 years and older): 2.5 mL four times daily after meals.
- Buccal: Use and dose must be determined by a doctor for children under 16 years old.
Special Cases:
- Elderly Patients: No specific dose adjustments are generally recommended, but monitoring for side effects is crucial.
- Patients with Renal Impairment: No specific dose adjustments are typically needed for topical or vaginal formulations.
- Patients with Hepatic Dysfunction: Use with caution in patients with hepatic impairment, as miconazole is primarily metabolized by the liver. Dosage adjustments may be necessary.
- Patients with Comorbid Conditions: Patients with diabetes should use vaginal miconazole under the supervision of a doctor, especially during pregnancy.
Clinical Use Cases
Miconazole is not typically used for intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations. Its primary use is in the treatment of fungal infections as described above.
Dosage Adjustments
Consider reducing dosage or increasing monitoring in patients with hepatic impairment. Dosage adjustments might be required based on drug interaction profiles, especially with drugs metabolized by CYP2C9 and CYP3A4.
Side Effects
Common Side Effects
- Topical: Burning, itching, irritation, redness at the application site.
- Vaginal: Vulvovaginal burning, itching, or irritation.
- Oral Gel: Nausea, vomiting, diarrhea, abdominal pain, changes in taste, headache, dry mouth.
Rare but Serious Side Effects
- Allergic reactions: Hives, rash, difficulty breathing, swelling of face, lips, tongue, or throat.
Long-Term Effects
No specific long-term adverse effects have been consistently reported.
Adverse Drug Reactions (ADR)
Severe allergic reactions, including anaphylaxis (rare).
Contraindications
- Hypersensitivity to miconazole or any component of the formulation.
- Concomitant use with certain medications metabolized by CYP3A4, such as cisapride, pimozide, astemizole, and terfenadine.
- Oral gel: Contraindicated in infants less than 4 months old or those with impaired swallowing reflex.
Drug Interactions
Miconazole can interact with several medications, particularly those metabolized by CYP2C9 and CYP3A4 enzymes. Clinically significant interactions include:
- Warfarin: Increased risk of bleeding.
- Sulfonylureas (e.g., chlorpropamide, glipizide): Increased risk of hypoglycemia.
- Certain antihistamines (e.g., astemizole, terfenadine): Increased risk of QT prolongation.
- Ergot alkaloids: Enhanced vasoconstriction.
- Statins: Increased risk of myopathy/rhabdomyolysis.
Pregnancy and Breastfeeding
- Pregnancy: Topical and vaginal miconazole are generally considered safe during pregnancy. Oral miconazole should be used with caution and only if the potential benefit outweighs the risk to the fetus.
- Breastfeeding: Topical and vaginal miconazole are considered compatible with breastfeeding. If applying to nipples, clean the area before breastfeeding.
Drug Profile Summary
- Mechanism of Action: Inhibits ergosterol biosynthesis, disrupting fungal cell membranes.
- Side Effects: Common: Local irritation (topical/vaginal), nausea, vomiting, diarrhea, abdominal pain, taste changes, headache (oral). Serious: Allergic reactions.
- Contraindications: Hypersensitivity, concomitant use with certain medications, oral gel in infants <4 months.
- Drug Interactions: Warfarin, sulfonylureas, certain antihistamines, ergot alkaloids, statins.
- Pregnancy & Breastfeeding: Topical/vaginal: generally safe. Oral: use with caution.
- Dosage: Varies based on formulation and indication (see Dosage section).
- Monitoring Parameters: INR (if co-administered with warfarin), blood glucose (if co-administered with sulfonylureas), signs of allergic reactions.
Popular Combinations
Miconazole is often used as a single agent. Some combination products include miconazole with other antifungals or corticosteroids for enhanced efficacy.
Precautions
- Assess for hypersensitivity before initiating therapy.
- Monitor for hepatic dysfunction and drug interactions, especially with drugs metabolized through CYP450 system.
- Avoid contact with eyes.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Miconazole?
A: Dosage varies greatly depending on the formulation and indication. See the Dosage section for specifics. Always consult product labeling and individualize therapy.
Q2: Can Miconazole be used during pregnancy?
A: Topical and vaginal formulations are generally considered safe during pregnancy. Consult a physician before using oral miconazole.
Q3: What are the common side effects of Miconazole?
A: Common side effects depend on the route of administration and include local irritation (topical/vaginal), nausea, vomiting, diarrhea, taste disturbance, headache, and dry mouth (oral).
Q4: How does Miconazole work?
A: It inhibits the synthesis of ergosterol, a vital component of fungal cell membranes, leading to fungal cell death.
Q5: What are the contraindications for Miconazole use?
A: Contraindications include known hypersensitivity to miconazole, concomitant use of certain medications metabolized by CYP3A4 (e.g., cisapride, pimozide), and use of the oral gel in infants less than 4 months old.
Q6: Does Miconazole interact with other medications?
A: Yes, significant drug interactions can occur, especially with warfarin, sulfonylureas, and certain antihistamines. Consult a drug interaction database before co-prescribing.
Q7: Can Miconazole be used in patients with liver disease?
A: Use with caution in patients with hepatic impairment. Monitor for adverse effects and consider dose adjustment.
Q8: Can Miconazole be used to treat all types of fungal infections?
A: Miconazole is effective against a range of fungal infections, but not all. It is crucial to correctly identify the causative organism to ensure appropriate treatment.
Q9: What should patients do if they experience side effects while using Miconazole?
A: Patients should report any adverse effects to their healthcare provider. Some side effects are mild and transient, but others may indicate a serious reaction requiring discontinuation of the medication.
