Tavaborole (Monograph)

Brand name: Kerydin
Drug class: Oxaboroles
Chemical name: 5-Fluoro-1,3-dihydro-1-hydroxy-2,1-benzoxaborole
Molecular formula: C₇H₆BFO₂
CAS number: 174671-46-6

Introduction

Antifungal; oxaborole (boron-containing compound).^{1 4}

Uses for Tavaborole

Onychomycosis

Topical treatment of onychomycosis of the toenails (tinea unguium, ringworm of the nail) caused by Trichophyton rubrum or T. mentagrophytes.¹

Tavaborole Dosage and Administration

Administration

Topical Administration

Apply 5% solution topically to affected toenails using dropper supplied by the manufacturer.¹

Do not administer orally or intravaginally;¹ do not apply topically to eyes.¹

Clean and dry toenails prior to application.¹

Using dropper supplied by the manufacturer, place solution on each affected toenail; use dropper tip to spread solution over entire toenail surface and under toenail tip.¹ More than a single drop of the solution may be necessary.¹

Avoid applying to skin that is not surrounding toenails being treated;¹ wipe excess solution from surrounding skin.¹

Allow solution to dry on the toenails (this may take a couple of minutes).¹

Wash hands with soap and water after applying the drug.¹

Dosage

Adults

Onychomycosis

Topical

Apply 5% solution to affected toenails once daily for 48 weeks.¹ Use amount sufficient to cover entire toenail surface and under toenail tip.¹ (See Topical Administration under Dosage and Administration.)

Special Populations

No special population dosage recommendations.¹

Cautions for Tavaborole

Contraindications

• Manufacturer states none.¹

Warnings/Precautions

Sensitivity Reactions

May cause skin irritation;^{1 13} no evidence that the drug causes contact sensitization.¹

Administration Precautions

For topical use only.¹ Do not use orally or intravaginally;¹ do not apply to eyes.¹

Selection and Use of Antifungals

Prior to treatment of onychomycosis, confirm diagnosis by direct microscopic examination of scrapings from infected toenails mounted in potassium hydroxide (KOH) or by culture.^{8 9 10 11 12}

Specific Populations

Pregnancy

Category C.¹

Lactation

Not known whether distributed into human milk following topical application.¹ Use with caution in nursing women.¹

Pediatric Use

Safety and efficacy not established in pediatric patients.¹

Geriatric Use

No overall differences in safety and efficacy in older adults relative to younger adults observed in clinical trials, but greater sensitivity of some older individuals cannot be ruled out.¹

Common Adverse Effects

Application site exfoliation,¹ ingrown toenail,¹ application site erythema,¹ application site dermatitis.¹

Drug Interactions

Does not inhibit CYP2A6, 2D6, or 2E1 and does not induce CYP1A2, 2B6, 2C8, 2C9, 2C19, or 3A4/5 in vitro at therapeutic concentrations.^{1 13 15}

No formal drug interaction studies to date.¹³

Tavaborole Pharmacokinetics

Absorption

Bioavailability

Following topical application of 5% tavaborole solution to toenails, the drug penetrates the nail plate and low concentrations are absorbed systemically.^{5 15}

Mean peak plasma concentration was 3.54 ng/mL (range 0.618–10.2 ng/mL) after a single dose and 5.17 ng/mL (range 1.51–12.8 ng/mL) after 14 consecutive days of once-daily topical administration of the 5% solution.¹

Median time to peak plasma concentration was 8.03 hours (range 0.47–24 hours) following 14 consecutive days of once-daily topical administration.⁵

Steady-state concentrations achieved after 14 days of once-daily topical application.¹

Elimination

Metabolism

Following systemic absorption, tavaborole undergoes extensive systemic metabolism.^{1 15}

Elimination Route

Systemically absorbed drug is principally eliminated by the kidneys.^{1 15}

Half-life

Mean terminal plasma half-life was 28.5 hours following 14 consecutive days of once-daily topical application to toenails.^{5 15}

Stability

Storage

Topical

Solution

20–25°C (may be exposed to 15–30°C).¹

The 5% solution contains alcohol and is flammable;¹ do not store or use near heat or open flame.¹

Keep bottle tightly closed;¹ discard bottle within 3 months after insertion of dropper.¹

Actions and Spectrum

• Boron-containing oxaborole antifungal.^{1 4 6}

• Integration of boron into the cyclic structure of a molecule allows for greater stability, greater physiologic availability at required site of action, and effective target binding capacity and selectivity.⁴

• Exerts antifungal activity by inhibiting an aminoacyl-transfer ribonucleic acid (tRNA) synthetase (AARS), resulting in fungal protein synthesis inhibition.¹ Inhibits editing domain of leucyl-tRNA synthetase;⁴ exhibits good relative selectivity for this fungal enzyme.⁴

• Has antifungal activity against some dermatophytes, including T. mentagrophytes and T. rubrum.^{1 4 14} Also has in vitro activity against Candida albicans.^{4 14}

• Antifungal activity not affected by presence of keratin.⁵

• No evidence to date that T. mentagrophytes or T. rubrum develops resistance to tavaborole following long-term topical treatment of onychomycosis caused by these dermatophytes.¹

Importance of using tavaborole topical solution only for the condition prescribed.¹

Advise patients that tavaborole topical solution is for external use only and to avoid contact with eyes, mouth, or vagina.¹

Advise patients to avoid applying the solution to skin other than skin immediately surrounding treated toenails, and to wipe away excess solution from surrounding skin using a tissue.¹

Importance of applying tavaborole topical solution with the dropper provided by the manufacturer and importance of not using the dropper for any other purpose.¹

Advise patients to ensure toenails are clean and dry prior to application of the drug.¹

Advise patients to wash hands with soap and water following application of the drug.¹

Advise patients that tavaborole topical solution is flammable and should not be stored or used near heat or open flame.¹

Importance of informing clinician if area of application shows signs of persistent irritation (e.g., redness, itching, swelling).¹

Importance of informing clinician of existing or contemplated concomitant therapy, including prescription and OTC drugs and dietary or herbal supplements, as well as any concomitant illnesses.¹

Importance of women informing their clinician if they are or plan to become pregnant or plan to breast-feed. ¹

Importance of informing patients of other important precautionary information.¹ (See Cautions.)

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

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