Griseofulvin Micr 500mg Tablets
It is used to treat fungal infections.
Drug Class
Antifungal
Pharmacologic Class
Antifungal, Mitotic Inhibitor
Pregnancy Category
X
FDA Approved
Jan 1959
DEA Schedule
Not Controlled
Overview
What is this medicine?
Griseofulvin is an antifungal medication used to treat fungal infections of the skin, hair, and nails. It works by stopping the growth of the fungus. It's important to take this medicine for the full prescribed time, even if your symptoms improve, to ensure the infection is completely cleared.
How to Use This Medicine
Taking Your Medication
To use this medication correctly, follow your doctor's instructions and read all the information provided. Discuss with your doctor or pharmacist whether to take this medication with food or on an empty stomach. Continue taking the medication as directed, even if your symptoms improve.
Storing and Disposing of Your Medication
Store this medication at room temperature in a dry location, avoiding bathrooms. Keep all medications in a secure place, out of reach of children and pets. Dispose of unused or expired medications properly. Do not flush them down the toilet or pour them down the drain unless instructed to do so. If you have questions about disposal, consult your pharmacist. You may also have access to local drug take-back programs.
Missing a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Avoid taking two doses at once or taking extra doses.
To use this medication correctly, follow your doctor's instructions and read all the information provided. Discuss with your doctor or pharmacist whether to take this medication with food or on an empty stomach. Continue taking the medication as directed, even if your symptoms improve.
Storing and Disposing of Your Medication
Store this medication at room temperature in a dry location, avoiding bathrooms. Keep all medications in a secure place, out of reach of children and pets. Dispose of unused or expired medications properly. Do not flush them down the toilet or pour them down the drain unless instructed to do so. If you have questions about disposal, consult your pharmacist. You may also have access to local drug take-back programs.
Missing a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Avoid taking two doses at once or taking extra doses.
Lifestyle & Tips
- Take with a fatty meal (e.g., milk, ice cream, peanut butter) to improve absorption and effectiveness.
- Avoid alcohol during treatment and for several days after stopping, as it can cause a disulfiram-like reaction (flushing, nausea, vomiting, rapid heartbeat).
- Avoid prolonged exposure to natural or artificial sunlight (tanning beds) as this medication can make your skin more sensitive to light, leading to severe sunburn. Use sunscreen and wear protective clothing.
- If you are taking oral contraceptives, use an alternative or additional method of birth control during treatment and for one month after stopping, as griseofulvin can reduce their effectiveness.
- Do not become pregnant while taking this medication or for at least one month after stopping it, as it can cause birth defects.
Available Forms & Alternatives
Dosing & Administration
Adult Dosing
Standard Dose:
500 mg daily in a single dose or divided doses for tinea corporis, tinea cruris, tinea pedis; 750 mg to 1000 mg daily in divided doses for tinea capitis, tinea unguium (onychomycosis)
Dose Range:
500 - 1000 mg
Condition-Specific Dosing:
tinea_corporis_cruris_pedis:
500 mg daily
tinea_capitis_unguium:
750-1000 mg daily
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established
Child:
10-15 mg/kg/day (microsize) in a single dose or divided doses
Adolescent:
10-15 mg/kg/day (microsize) up to adult dose
Dose Adjustments
Renal Impairment:
Mild:
No specific adjustment recommended
Moderate:
No specific adjustment recommended
Severe:
No specific adjustment recommended, use with caution
Dialysis:
Not significantly removed by dialysis; no specific adjustment, use with caution
Hepatic Impairment:
Mild:
Use with caution
Moderate:
Use with caution, monitor liver function closely
Severe:
Contraindicated in severe liver disease
Confidence:
Medium
Pharmacology
Mechanism of Action
Griseofulvin is a fungistatic agent that inhibits fungal cell division by disrupting the mitotic spindle structure. It binds to keratin in newly forming skin, hair, and nails, making them resistant to fungal invasion. It is deposited in keratin precursor cells, and as these cells mature, they become highly resistant to fungal infections.
Pharmacokinetics
Absorption:
Bioavailability:
Variable (25-70%), significantly enhanced by high-fat meals
Tmax:
Approximately 4 hours (range 2-8 hours)
FoodEffect:
Absorption is significantly increased (up to 2-fold) when taken with a high-fat meal.
Distribution:
Vd:
Not readily available, but distributes widely into keratinized tissues
ProteinBinding:
Approximately 80%
CnssPenetration:
Limited
Elimination:
HalfLife:
Approximately 9-24 hours
Clearance:
Not readily available
ExcretionRoute:
Renal (less than 1% as unchanged drug), fecal (major route for metabolites)
Unchanged:
Less than 1%
Pharmacodynamics
OnsetOfAction:
Weeks to months, depending on the site of infection (e.g., 4-8 weeks for skin, 4-6 months for fingernails, 6-12 months for toenails)
PeakEffect:
Not applicable in terms of acute effect; peak therapeutic effect is observed after prolonged treatment as new keratinized tissue grows
DurationOfAction:
Persists in keratinized tissues as long as the drug is administered and for some time after discontinuation, depending on the turnover rate of the infected tissue.
Confidence:
Medium
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Help Right Away
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor or seek medical attention immediately:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of lupus, including:
+ Rash on the cheeks or other body parts
+ Easy sunburn
+ Muscle or joint pain
+ Chest pain or shortness of breath
+ Swelling in the arms or legs
Signs of liver problems, such as:
+ Dark urine
+ Tiredness
+ Decreased appetite
+ Upset stomach or stomach pain
+ Light-colored stools
+ Vomiting
+ Yellow skin or eyes
Feeling confused
Abnormal burning, numbness, or tingling sensations
Redness or white patches in the mouth or throat
Severe skin reaction (Stevens-Johnson syndrome/toxic epidermal necrolysis), characterized by:
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ Red or irritated eyes
+ Sores in the mouth, throat, nose, or eyes
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people experience no side effects or only mild ones, others may have more bothersome symptoms. If you experience any of the following side effects or any other unusual symptoms, contact your doctor or seek medical attention:
Headache
Dizziness, tiredness, or weakness
Diarrhea
Stomach pain
Upset stomach
Vomiting
Trouble sleeping
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects not mentioned here. If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor or seek medical attention immediately:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of lupus, including:
+ Rash on the cheeks or other body parts
+ Easy sunburn
+ Muscle or joint pain
+ Chest pain or shortness of breath
+ Swelling in the arms or legs
Signs of liver problems, such as:
+ Dark urine
+ Tiredness
+ Decreased appetite
+ Upset stomach or stomach pain
+ Light-colored stools
+ Vomiting
+ Yellow skin or eyes
Feeling confused
Abnormal burning, numbness, or tingling sensations
Redness or white patches in the mouth or throat
Severe skin reaction (Stevens-Johnson syndrome/toxic epidermal necrolysis), characterized by:
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ Red or irritated eyes
+ Sores in the mouth, throat, nose, or eyes
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people experience no side effects or only mild ones, others may have more bothersome symptoms. If you experience any of the following side effects or any other unusual symptoms, contact your doctor or seek medical attention:
Headache
Dizziness, tiredness, or weakness
Diarrhea
Stomach pain
Upset stomach
Vomiting
Trouble sleeping
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects not mentioned here. If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Seek Immediate Medical Attention If You Experience:
- Yellowing of skin or eyes (jaundice)
- Dark urine or pale stools
- Unusual tiredness or weakness
- Persistent nausea, vomiting, or loss of appetite
- Fever, chills, sore throat, or unusual bleeding/bruising (signs of blood problems)
- Severe skin rash, blistering, or peeling
- Severe headache or confusion
- Numbness or tingling in hands or feet
- Signs of an allergic reaction (hives, swelling of face/lips/tongue/throat, difficulty breathing)
Before Using This Medicine
Before Taking This Medication: Important Information to Share with Your Doctor
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced.
Certain health conditions, including liver disease or porphyria.
If you are pregnant or think you may be pregnant. Note that this medication should not be taken during pregnancy.
If you plan to become pregnant within one month after your last dose of this medication.
* If you are breast-feeding or plan to breast-feed.
This list is not exhaustive, and it is crucial to discuss all your medications (including prescription, over-the-counter, natural products, and vitamins) and health problems with your doctor and pharmacist. They will help determine if it is safe to take this medication with your other medications and health conditions. Never start, stop, or change the dose of any medication without first consulting your doctor.
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced.
Certain health conditions, including liver disease or porphyria.
If you are pregnant or think you may be pregnant. Note that this medication should not be taken during pregnancy.
If you plan to become pregnant within one month after your last dose of this medication.
* If you are breast-feeding or plan to breast-feed.
This list is not exhaustive, and it is crucial to discuss all your medications (including prescription, over-the-counter, natural products, and vitamins) and health problems with your doctor and pharmacist. They will help determine if it is safe to take this medication with your other medications and health conditions. Never start, stop, or change the dose of any medication without first consulting your doctor.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication. If you are taking this drug for an extended period, your doctor may recommend regular blood tests to monitor your condition.
Before consuming alcohol, discuss the potential risks with your doctor. Additionally, be aware that this medication can increase your sensitivity to the sun, making it easier to get sunburned. To minimize this risk, avoid exposure to direct sunlight, sunlamps, and tanning beds, and use protective measures such as sunscreen, clothing, and eyewear that provide adequate sun protection.
Do not take this medication for longer than prescribed, as this can increase the risk of a second infection. If you have a history of lupus, this drug may cause your condition to become active or worsen. Immediately report any new or worsening symptoms to your doctor.
When taking this medication, be aware that birth control pills and other hormone-based birth control methods may be less effective in preventing pregnancy. To minimize the risk of unintended pregnancy, use an additional form of birth control, such as a condom, while taking this drug.
This medication can potentially harm an unborn baby if taken during pregnancy. If you are pregnant or planning to become pregnant, discuss the risks with your doctor. If your partner may become pregnant, use birth control while taking this medication and for 6 months after your last dose. If your partner becomes pregnant, notify your doctor immediately.
Before consuming alcohol, discuss the potential risks with your doctor. Additionally, be aware that this medication can increase your sensitivity to the sun, making it easier to get sunburned. To minimize this risk, avoid exposure to direct sunlight, sunlamps, and tanning beds, and use protective measures such as sunscreen, clothing, and eyewear that provide adequate sun protection.
Do not take this medication for longer than prescribed, as this can increase the risk of a second infection. If you have a history of lupus, this drug may cause your condition to become active or worsen. Immediately report any new or worsening symptoms to your doctor.
When taking this medication, be aware that birth control pills and other hormone-based birth control methods may be less effective in preventing pregnancy. To minimize the risk of unintended pregnancy, use an additional form of birth control, such as a condom, while taking this drug.
This medication can potentially harm an unborn baby if taken during pregnancy. If you are pregnant or planning to become pregnant, discuss the risks with your doctor. If your partner may become pregnant, use birth control while taking this medication and for 6 months after your last dose. If your partner becomes pregnant, notify your doctor immediately.
Overdose Information
Overdose Symptoms:
- Nausea
- Vomiting
- Diarrhea
- Headache
- Confusion
What to Do:
Seek immediate medical attention or call a Poison Control Center (1-800-222-1222). Treatment is generally supportive.
Drug Interactions
Major Interactions
Moderate Interactions
- Cyclosporine (decreased cyclosporine levels)
- Salicylates (decreased salicylate levels)
- Theophylline (decreased theophylline levels)
Confidence Interactions
Monitoring
Baseline Monitoring
Liver Function Tests (ALT, AST, bilirubin)
Rationale: To assess baseline hepatic function, as griseofulvin is metabolized by the liver and can cause hepatotoxicity.
Timing: Prior to initiation of therapy
Complete Blood Count (CBC) with differential
Rationale: To assess baseline hematologic status, as griseofulvin can cause leukopenia or neutropenia.
Timing: Prior to initiation of therapy
Renal Function Tests (BUN, creatinine)
Rationale: To assess baseline renal function, though renal excretion is minor, caution is advised in severe impairment.
Timing: Prior to initiation of therapy
Routine Monitoring
Liver Function Tests (ALT, AST, bilirubin)
Frequency: Periodically, especially during prolonged therapy (e.g., every 4-8 weeks for first few months, then every 3-6 months)
Target: Within normal limits
Action Threshold: Discontinue if significant elevation (e.g., >3x ULN) or clinical signs of liver injury occur.
Complete Blood Count (CBC) with differential
Frequency: Periodically, especially during prolonged therapy (e.g., every 4-8 weeks for first few months, then every 3-6 months)
Target: Within normal limits
Action Threshold: Discontinue if significant leukopenia, neutropenia, or other blood dyscrasias develop.
Symptom Monitoring
- Signs of liver injury (e.g., persistent nausea, anorexia, dark urine, jaundice, clay-colored stools)
- Signs of blood dyscrasias (e.g., fever, sore throat, unusual bleeding or bruising, fatigue)
- Severe skin reactions (e.g., rash, blistering, peeling, Stevens-Johnson syndrome, toxic epidermal necrolysis)
- Photosensitivity (severe sunburn-like reaction)
- Gastrointestinal upset (nausea, vomiting, diarrhea)
- Central nervous system effects (headache, dizziness, confusion, insomnia)
- Allergic reactions (hives, swelling, difficulty breathing)
Special Patient Groups
Pregnancy
Contraindicated in pregnancy (Pregnancy Category X) due to significant teratogenic risk, including conjoined twins and other severe fetal abnormalities. Women of childbearing potential should use effective contraception during treatment and for at least one month after stopping griseofulvin. Men whose partners are of childbearing potential should also be advised to use contraception during treatment and for 6 months after stopping.
Trimester-Specific Risks:
First Trimester:
High risk of severe birth defects, including conjoined twins, due to teratogenic effects.
Second Trimester:
Risk of fetal harm remains, though specific defects may vary.
Third Trimester:
Risk of fetal harm remains.
Lactation
Griseofulvin is excreted into breast milk. Due to potential for serious adverse effects in the nursing infant (e.g., carcinogenicity, hepatotoxicity, allergic reactions), breastfeeding is generally not recommended during treatment. A decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.
Infant Risk:
L4 (Potentially Hazardous) - Potential for serious adverse effects in the infant; avoid use.
Pediatric Use
Griseofulvin microsize is approved for use in children. Dosing is weight-based (10-15 mg/kg/day). Long-term safety data in children are limited, and monitoring for adverse effects (especially liver and blood counts) is important.
Geriatric Use
No specific dose adjustments are generally required based on age alone. However, elderly patients may have age-related decreases in hepatic or renal function, or may be on multiple medications, increasing the risk of adverse effects or drug interactions. Monitor liver function and CBC closely.
Clinical Information
Clinical Pearls
- Griseofulvin is fungistatic, not fungicidal, meaning it inhibits fungal growth rather than killing it directly. This contributes to the long treatment durations required.
- Absorption is highly variable and significantly improved by taking the medication with a high-fat meal. This is a critical patient education point for efficacy.
- Treatment durations are prolonged, often several months for nail infections (6-12 months for toenails) and weeks to months for skin/hair infections, requiring high patient adherence.
- Photosensitivity is a common side effect; advise patients to use sunscreen and protective clothing.
- Due to its teratogenicity, strict contraception is essential for both male and female patients of reproductive potential during and after treatment.
- Griseofulvin can induce hepatic enzymes, leading to interactions with drugs like warfarin and oral contraceptives. Monitor INR for warfarin users and advise alternative contraception.
Alternative Therapies
- Terbinafine (oral)
- Itraconazole (oral)
- Fluconazole (oral)
- Ketoconazole (oral - less common due to hepatotoxicity concerns)
- Topical antifungals (for superficial infections, e.g., azoles, allylamines)
Cost & Coverage
Average Cost:
Varies widely, typically $20-$100 per 30 tablets
Generic Available:
Yes
Insurance Coverage:
Tier 1 or Tier 2 (Generic)
General Drug Facts
If your symptoms or health issues persist or worsen, it is essential to contact your doctor promptly. To ensure safe and effective treatment, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so it's a good idea to check with your pharmacist for more information. If you have any questions or concerns about this medication, don't hesitate to discuss them with your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek emergency medical attention. When seeking help, be prepared to provide details about the overdose, including the medication taken, the amount, and the time it occurred.