Systemic Nail Fungus Treatment Explained

Nail fungus, medically known as onychomycosis, is a common and often persistent infection that affects the nails of the fingers and toes. While topical treatments can be effective for mild cases, more severe or widespread infections often require a more robust approach. Systemic treatment, involving oral antifungal medications, is frequently the most effective method for eradicating this stubborn condition. This article will delve into the world of systemic nail fungus treatment, focusing primarily on the widely used and highly effective antifungal drug, terbinafine.

Understanding Systemic Antifungal Therapy

Systemic antifungal therapy involves taking medication orally, which is then absorbed into the bloodstream and distributed throughout the body, including the nail bed and nail matrix. This allows the medication to reach the fungal infection at its source, directly targeting the pathogens responsible for the onychomycosis. Unlike topical treatments that struggle to penetrate the dense nail plate, oral medications can achieve therapeutic concentrations within the nail, leading to a higher rate of fungal eradication.

Terbinafine: The Gold Standard for Nail Fungus

Terbinafine, marketed under brand names such as Lamisil, stands out as the most common and effective systemic treatment for nail fungus, particularly for infections caused by dermatophytes, which are the most prevalent culprits. Terbinafine belongs to a class of drugs called allylamines and works by having a fungicidal effect on dermatophytes and moulds, meaning it actively kills these fungi. It also exhibits a fungistatic effect on yeasts, inhibiting their growth and reproduction.

The pharmacokinetic profile of terbinafine is particularly well-suited for treating nail infections. After oral administration, terbinafine is rapidly absorbed and detected in the skin's stratum corneum, hair, and nails. This occurs partly through secretion in sebum (oil) and partly through diffusion. A standard daily dose of 250 mg of terbinafine typically achieves sufficient therapeutic concentrations in the nail plate.

Treatment Duration and Efficacy

The duration of terbinafine treatment is crucial for achieving a successful outcome. For fungal infections affecting the fingernails, a course of 250 mg daily for six weeks is generally recommended. However, toenail infections, which are more common and tend to grow more slowly, require a longer treatment period of 12 weeks at the same daily dosage. It's important for patients to understand that even after completing the course of medication, the infected nail will not immediately appear normal. The body needs time to grow out the new, healthy nail, a process that can take 6-8 months for fingernails and 12-18 months for toenails. This extended timeline should be clearly communicated to patients to manage expectations and ensure adherence to the treatment plan.

Clinical studies have demonstrated the high efficacy of terbinafine. Between 75% and 85% of patients experience mycological and clinical cure of dermatophyte infections one to two years after completing the treatment. While terbinafine can also be used for yeast and mould infections, its effectiveness is generally lower in these cases compared to dermatophyte infections.

Side Effects and Precautions

Terbinafine is generally well-tolerated, with a low incidence of side effects. The most commonly reported side effect is taste disturbance, affecting about 1% of patients. Fortunately, this usually resolves after the medication is stopped, and persistent taste loss has not been reported. More serious side effects, such as haematological (blood-related) or dermatological (skin-related) reactions, are rare, occurring in fewer than 0.01% of patients. For otherwise healthy individuals, routine laboratory monitoring of blood tests during terbinafine treatment is not typically necessary.

Drug Interactions

Terbinafine is metabolised in the liver, primarily through oxidation and to a lesser extent via the cytochrome P-450 system. This metabolic pathway results in relatively few interactions with other medications. However, there is some evidence to suggest that terbinafine may induce the metabolic breakdown of cyclosporine, an immunosuppressant drug. Patients taking cyclosporine should have their cyclosporine levels monitored while undergoing terbinafine treatment. Terbinafine can also inhibit the metabolism of drugs broken down by the liver enzyme cytochrome P-2D6. This includes certain antiarrhythmics, beta-blockers, and antidepressants. The clinical significance of these potential interactions is still considered uncertain, but it is always advisable for patients to inform their doctor about all medications they are currently taking.

Other Systemic Antifungal Options

Ketoconazole

Ketoconazole (e.g., Fungoral) is another oral antifungal that has activity against both dermatophytes and yeasts. For nail infections, treatment courses typically range from 6 to 12 months. However, due to its potential for liver toxicity, liver enzyme levels in the blood must be measured before and during treatment. Ketoconazole also inhibits cytochrome P-3A4, a liver enzyme that metabolises many drugs, leading to potential serious interactions with medications such as cyclosporine, cisapride, terfenadine, and certain statins. Consequently, ketoconazole tablets are considered a specialist preparation and are rarely used as a first-line treatment for nail fungus.

Itraconazole and Fluconazole

Itraconazole (e.g., Sporanox) and fluconazole (e.g., Diflucan) are generally considered more effective against Candida infections (yeast infections) than terbinafine. However, they are not currently registered for the treatment of nail fungus in many regions. Similar to ketoconazole, itraconazole also inhibits cytochrome P-3A4, posing a risk of drug interactions.

Griseofulvin

In the past, griseofulvin was the only available systemic antifungal for use. For toenail infections, a treatment course of 9 to 12 months with griseofulvin yielded a cure rate of only 20% to 40%. Due to this modest efficacy, griseofulvin is no longer recommended for the treatment of nail fungus.

Surgical Intervention and Nail Removal

It is worth noting that surgical removal of a fungal-infected nail, whether with or without concurrent systemic antifungal treatment, has not demonstrated significant efficacy. Therefore, this approach is generally not recommended for treating onychomycosis.

Frequently Asked Questions

Q1: How long does it take for my nails to look normal after taking terbinafine?

A1: It typically takes 6-8 months for fingernails and 12-18 months for toenails to grow out completely healthy after completing a course of terbinafine, as the new nail needs to replace the infected nail tissue.

Q2: Can terbinafine cause liver damage?

A2: While serious liver-related side effects are rare (affecting less than 0.01% of patients), it's important to be aware of the possibility. If you have pre-existing liver conditions or experience symptoms like jaundice, dark urine, or persistent nausea, consult your doctor immediately. For most healthy individuals, monitoring is not required.

Q3: Are there any natural remedies that work as well as terbinafine?

A3: While some natural remedies are explored, scientific evidence supporting their efficacy for treating nail fungus to the same extent as terbinafine is limited. Systemic treatments like terbinafine are considered the most effective option for moderate to severe infections.

Q4: Can I drink alcohol while taking terbinafine?

A4: It is advisable to limit alcohol consumption while taking terbinafine, as both are metabolised by the liver. Excessive alcohol intake could potentially increase the risk of liver-related side effects. Discuss this with your doctor for personalised advice.

Q5: What happens if I miss a dose of terbinafine?

A5: If you miss a dose, take it as soon as you remember, unless it is almost time for your next dose. In that case, skip the missed dose and continue with your regular schedule. Do not take a double dose to make up for a missed one.

Conclusion

Systemic treatment, particularly with terbinafine, remains the cornerstone of effective management for most cases of nail fungus. Its ability to reach the infected nail bed, combined with a favourable safety profile and high cure rates, makes it the preferred choice for healthcare professionals. Understanding the treatment duration, potential side effects, and the importance of completing the full course of medication is vital for patients seeking to overcome this persistent fungal infection and achieve healthy, clear nails.