Griseofulvin FP Tablet

Introduction

Griseofulvin (Microsize) is an antifungal medication used to treat various dermatophyte infections, including those affecting the skin, hair, and nails. It works by inhibiting the growth of fungi, making it particularly useful for treating conditions like ringworm, athlete's foot, jock itch, and fungal infections of the scalp and nails. The "microsize" formulation refers to the particle size of the drug, which enhances absorption and bioavailability.

Uses

Griseofulvin (Microsize) is used for the treatment of:

Tinea corporis (ringworm)
Tinea pedis (athlete's foot)
Tinea cruris (jock itch)
Tinea barbae (fungal infection of the beard area)
Tinea capitis (scalp ringworm)
Tinea unguium (onychomycosis or nail infections)

It is typically prescribed when topical treatments are ineffective or in cases of widespread infection.

Brand Name	Griseofulvin FP
Type	Tablet
Weight	500 mg
Generic	Griseofulvin [Microsize]
Manufacturer	Bristol Pharmaceuticals Ltd.
Available in	English বাংলা

Mechanism of Action

Griseofulvin works by binding to the keratin in newly formed skin, hair, and nails, making them resistant to fungal invasion. It interferes with the mitotic spindle in fungal cells, inhibiting fungal cell division. Over time, the infected tissues are replaced by healthy, fungus-free cells as the drug accumulates in keratin-rich tissues.

How Long Does It Take to Work?

The onset of action varies depending on the site of infection. Improvement in skin infections (e.g., tinea corporis) may be seen within 2-4 weeks. Nail infections (tinea unguium) may take several months (6-12 months) to fully clear due to the slow growth rate of nails. Consistent use of the medication is essential for full efficacy.

Absorption

Griseofulvin (Microsize) is absorbed in the gastrointestinal tract, with enhanced absorption when taken with a high-fat meal. Microsize particles improve absorption compared to larger particle formulations, but absorption is still variable. The bioavailability of the drug is around 25-70%.

Route of Elimination

Griseofulvin is metabolized in the liver and primarily excreted through the urine. Small amounts may also be excreted via feces and sweat. The drug’s metabolites are mostly inactive.

Dosage

Accurate diagnosis of the infecting organism is essential. Identification should be made either by direct microscopic examination of a mounting of infected tissue in a solution of potassium hydroxide or by culture on an appropriate medium.

Medication must be continued until the infecting organism is completely eradicated as indicated by appropriate clinical or laboratory examination. Representative treatment periods are tinea capitis, 4 to 6 weeks; tinea corporis, 2 to 4 weeks; tinea pedis, 4 to 8 weeks; tinea unguium- depending on rate of growth- fingernails, at least 4 months; toenails, at least 6months.

General measures in regard to hygiene should be observed to control sources of infection or reinfection. Concomitant use of appropriate topical agents is usually required, particularly in treatment of tinea pedis since in some forms of athlete's foot, yeasts and bacteria may be involved. Griseofulvin will not eradicate the bacterial or monilial infection.

Adults: A daily dose of 500 mg will give a satisfactory response in most patients with tinea corporis, tinea cruris, and tinea capitis. For those fungus infections more difficult to eradicate such as tinea pedis and tinea unguium, a daily dose of 1.0 gm is recommended.

Children: Approximately 5 mg per pound of body weight per day is an effective dose for most children. On this basis the following dosage schedule for children is suggested:

Children weighing 30 to 50 pounds: 125 mg to 250 mg daily.
Children weighing over 50 pounds: 250 mg to 500 mg daily.

The dosage of griseofulvin (Microsize) depends on the type and severity of the infection:

Tinea corporis, tinea cruris, and tinea pedis: 500 mg to 1 g daily in single or divided doses for 2-4 weeks.
Tinea capitis: 500 mg to 1 g daily for 4-6 weeks or longer.
Tinea unguium: 500 mg to 1 g daily for 6 months (finger) or up to 12 months (toes).

For pediatric patients, the dosage is typically 10 mg/kg/day, but adjustments should be made based on the child’s weight and the severity of the infection.

Administration

Griseofulvin (Microsize) is administered orally and should be taken with a high-fat meal to enhance absorption. It is available in tablet or suspension forms. Treatment should be continued for the full prescribed duration, even if symptoms improve early, to ensure complete eradication of the infection.

Side Effects

Common side effects of griseofulvin include:

Headache
Nausea and vomiting
Diarrhea
Fatigue
Dizziness

Less common but more serious side effects may include:

Photosensitivity (increased sensitivity to sunlight)
Rash or hives
Hepatotoxicity (liver damage)
Proteinuria (protein in the urine)
Leukopenia (low white blood cell count)

Toxicity

Griseofulvin toxicity is rare but may occur at high doses or with prolonged use. Symptoms of overdose include nausea, vomiting, diarrhea, dizziness, and headache. Hepatotoxicity and hematologic changes, such as leukopenia, are potential complications. In cases of overdose, supportive care and symptomatic treatment are recommended.

Precautions

Griseofulvin should be used with caution in patients with:

Liver disease
Systemic lupus erythematosus
A history of photosensitivity reactions
Blood dyscrasias (abnormalities in blood cell formation)

Patients should avoid prolonged exposure to sunlight or tanning beds, as griseofulvin may increase sensitivity to ultraviolet (UV) light.

Interaction

Griseofulvin may interact with several medications:

Oral contraceptives: Griseofulvin may reduce the efficacy of birth control pills, increasing the risk of pregnancy.
Warfarin: Griseofulvin may reduce the anticoagulant effects of warfarin, requiring dose adjustments.
Barbiturates: Concomitant use with barbiturates may reduce the effectiveness of griseofulvin.
Alcohol: May increase the risk of a disulfiram-like reaction (nausea, vomiting, flushing).

Disease Interaction

Griseofulvin should be used cautiously in patients with:

Liver disease: Griseofulvin is metabolized in the liver, so patients with hepatic impairment are at increased risk for toxicity.
Systemic lupus erythematosus: Griseofulvin may exacerbate the condition.
Porphyria: It may worsen symptoms in patients with porphyria due to its effect on hepatic enzymes.

Drug Interaction

Griseofulvin may interact with the following drugs:

Barbiturates: May decrease the efficacy of griseofulvin.
Oral contraceptives: May reduce contraceptive efficacy, increasing the risk of pregnancy.
Warfarin: May reduce the anticoagulant effects of warfarin.
Ciclosporin: May decrease the plasma concentration of ciclosporin.

Food Interactions

Griseofulvin should be taken with a high-fat meal to improve absorption. Fat enhances the bioavailability of the medication and helps it reach therapeutic levels in the bloodstream more effectively.

Pregnancy Use

Griseofulvin is contraindicated during pregnancy, especially during the first trimester, as it may cause fetal harm, including teratogenic effects. Women of childbearing potential should use effective contraception during treatment and for at least one month after discontinuation of the medication.

Lactation Use

It is not known whether griseofulvin is excreted in breast milk. Caution is advised when administering the drug to breastfeeding mothers, as potential adverse effects on the nursing infant are unknown. Consulting a healthcare provider is recommended.

Acute Overdose

In cases of acute overdose, symptoms may include nausea, vomiting, diarrhea, dizziness, and confusion. Hepatotoxicity and central nervous system effects are possible. Treatment should be supportive, with close monitoring of liver function and fluid-electrolyte balance.

Contraindication

Griseofulvin (Microsize) is contraindicated in patients with:

Hypersensitivity to griseofulvin or any of its components
Liver failure or severe hepatic dysfunction
Porphyria
Pregnancy, due to the risk of teratogenic effects

Use Direction

Griseofulvin should be taken exactly as prescribed by a healthcare provider. It is important to complete the full course of therapy, even if symptoms improve earlier. The medication should be taken with a high-fat meal to enhance absorption, and missed doses should be taken as soon as remembered, unless it is close to the time for the next dose.

Storage Conditions

Griseofulvin (Microsize) should be stored at room temperature (15°C to 30°C) in a tightly sealed container, away from moisture and light. It should be kept out of reach of children.

Volume of Distribution

The volume of distribution of griseofulvin is moderate, as it is distributed mainly into keratin-rich tissues such as skin, hair, and nails. It also accumulates in adipose tissues, which is enhanced when taken with a high-fat meal.

Half-Life

Griseofulvin has a half-life of approximately 9-24 hours. The elimination half-life may be prolonged in patients with hepatic impairment or in cases of chronic use.

Clearance

Griseofulvin is metabolized primarily by the liver and is eliminated through urine as inactive metabolites. Clearance may be reduced in patients with liver dysfunction, requiring dosage adjustments.

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