Terbinafine DMSO (1.6%, 10%)

Route: Topical transungual (nail) application.

• Clean and dry affected nail(s) thoroughly before application.
• File the nail surface with an emery board before the first application each week to thin the nail plate and reduce barrier thickness.
• Apply a thin layer of the solution to the entire nail surface, under the free edge (hyponychium), and adjacent skin once daily or as directed.
• Allow to dry completely (approximately 5–10 minutes) before covering.
• Do not wash treated nails for at least 1 hour after application.
• Wear gloves when applying if the treatment area is not the prescriber's hand; DMSO is rapidly absorbed through skin and may carry terbinafine systemically in the applicator.
• Avoid contact with mucous membranes and eyes.

Applied once daily to affected nail(s) as directed by the prescriber. The 1.6% concentration provides a lower-dose option for patients with mild-to-moderate onychomycosis or as adjunct to systemic therapy; the 10% concentration is for moderate-to-severe cases or as primary topical monotherapy. Treatment duration for onychomycosis is typically 48 weeks or longer (toenails); fingernail onychomycosis may respond within 24 weeks. The prescriber determines concentration, frequency, and duration.

• Terbinafine: Selectively inhibits fungal squalene epoxidase (an enzyme in the ergosterol biosynthesis pathway), with selectivity approximately 10,000-fold greater for fungal vs. human squalene epoxidase. Inhibition causes two lethal effects: (1) depletion of ergosterol, which is essential for fungal membrane integrity, fluidity, and function; and (2) accumulation of squalene to toxic intracellular concentrations, which disrupts membrane permeability and lysosomal function. The net result is fungicidal activity (cell death, not merely growth arrest) against T. rubrum and T. mentagrophytes, the primary dermatophytes causing onychomycosis.
• DMSO (penetration enhancement): DMSO is a small, amphiphilic molecule (MW 78 g/mol) that interacts with keratin's hydrogen-bonding network, disrupting protein conformational stability and swelling the nail plate; this increases the effective diffusion coefficient of terbinafine through nail keratin by orders of magnitude relative to aqueous or conventional solvent vehicles. DMSO also enhances the thermodynamic activity of terbinafine in the formulation, increasing the drug's tendency to partition into nail tissue.

Indication context: Terbinafine DMSO is prescribed for onychomycosis confirmed or suspected on clinical examination (and ideally confirmed by KOH preparation, PAS staining, or fungal culture) in patients who prefer or require topical therapy (e.g., contraindication to oral terbinafine due to hepatic disease, drug interactions, or patient preference). Topical therapy has lower systemic exposure than oral terbinafine and avoids hepatotoxicity risk; however, nail penetration remains the limiting factor. DMSO formulations are designed to overcome this pharmacokinetic barrier.

Monitoring:

• Clinical assessment of nail appearance (proximal clearing, reduction in discoloration/thickening/onycholysis) at 3–6-month intervals.
• KOH preparation or fungal culture can confirm mycological cure (absence of viable organisms).
• Hepatic function monitoring is not routinely required for topical application due to low systemic absorption; however, if impaired skin surrounds the nail, monitor for signs of systemic terbinafine exposure.
• Assess for contact irritation or sensitization to DMSO.

Contraindications:

• Known hypersensitivity to terbinafine or DMSO.
• Avoid use on open wounds or severely compromised periungual skin; excessive systemic DMSO/terbinafine absorption may occur.
• Pregnancy: terbinafine is not recommended during pregnancy (limited data); DMSO penetrates systemically; use only if benefit clearly outweighs risk per prescriber judgment.

Warnings & Precautions:

• DMSO characteristic odor: DMSO is excreted via lungs and skin, producing a garlic- or oyster-like odor that patients will notice on breath and skin after application; this is harmless but should be discussed with patients before prescribing.
• Systemic DMSO absorption: DMSO crosses all biological membranes; concurrent application of other medications to treated areas may result in inadvertent systemic absorption of those medications via DMSO enhancement—avoid other topicals in same area.
• Do not use DMSO on contaminated skin or with contaminated gloves; DMSO will carry contaminants transdermally.
• DMSO contact sensitivity: rare but possible; discontinue if erythema or urticaria develops.

Drug Interactions:

• DMSO may enhance dermal absorption of any concurrently applied topical agent; avoid concurrent topical application of other medications to the same site.
• Oral terbinafine (if used concurrently): additive antifungal activity but monitor for hepatotoxicity risk of systemic terbinafine component.

Common Side Effects: Garlic/oyster-like breath and body odor (DMSO-related, expected); local erythema, burning, or pruritus at application site; skin dryness or scaling around treated nail; rarely, contact dermatitis.

Store at room temperature (15–25°C). Keep in a tightly sealed, chemically resistant container (glass preferred; some plastics are incompatible with DMSO). Protect from light and heat. DMSO has a melting point of 18.5°C—the solution may solidify in cool environments; this is harmless; allow to come to room temperature before use. Do not freeze intentionally. Use within the beyond-use date assigned by Genesis Compounding per USP <795> standards. Keep out of reach of children.

Why is DMSO used as the vehicle instead of a regular cream?

The nail plate is one of the most challenging drug barriers in the body—it is a dense, cross-linked keratin matrix through which most conventional topical formulations cannot penetrate adequately. DMSO disrupts the keratin structure, swells the nail plate, and physically carries terbinafine through to the subungual space where the fungus lives. Without this enhanced penetration, most topical antifungals achieve insufficient nail concentrations to be fungicidal.

What is the garlic-like smell?

DMSO is metabolized to dimethylsulfide, which is excreted through the lungs and skin, producing a characteristic garlic or oyster-like odor. This is harmless and expected; it is not a sign of a problem. The odor diminishes as DMSO clears from the body.

How long will I need to use this?

Toenail onychomycosis typically requires 48 weeks (about 12 months) of treatment because the nail grows slowly. Fingernail infections may clear in 24 weeks. Clinical improvement is visible as the healthy new nail grows in from the proximal end. Do not stop treatment prematurely even if the nail looks better.

Is this FDA-approved?

Oral terbinafine tablets (Lamisil) are FDA-approved for onychomycosis. Ciclopirox lacquer (Penlac) and efinaconazole solution (Jublia) are FDA-approved topical options. Terbinafine in a DMSO vehicle is not FDA-approved as a finished dosage form; this is a patient-specific 503A compounded preparation from Genesis Compounding requiring a valid prescriber order.