Nurses Compass
Drug Guide
Terbinafine Hydrochloride
Classification
Therapeutic: Antifungal
Pharmacological: Allylamine antifungal
FDA Approved Indications
- Onychomycosis (nail fungus)
- Tinea corporis (ringworm), Tinea cruris (jock itch), Tinea pedis (athlete's foot)
Mechanism of Action
Inhibits fungal squalene epoxidase, leading to accumulation of squalene and inhibition of fungal ergosterol synthesis, disrupting cell membrane formation.
Dosage and Administration
Adult: 250 mg once daily for 6 weeks (onychomycosis fingernails) or 12 weeks (toenails).
Pediatric: Not generally recommended; consult guidelines.
Geriatric: Adjust based on renal and hepatic function, start at lower doses if needed.
Renal Impairment: Use with caution, adjust dose as needed.
Hepatic Impairment: Contraindicated in active liver disease; monitor liver function.
Pharmacokinetics
Absorption: Well absorbed orally, with increased absorption when taken with food.
Distribution: Extensively distributed in body tissues, especially keratin-containing tissues.
Metabolism: Hepatically metabolized via CYP enzymes, notably CYP2C9 and CYP1A2.
Excretion: Primarily via the urine (metabolites), small amount as unchanged drug in feces.
Half Life: approximately 200-400 hours (due to tissue accumulation).
Contraindications
- Active liver disease
- Hypersensitivity to terbinafine
Precautions
- Monitor liver function during therapy.
- Use with caution in hepatic impairment, and in patients taking other hepatotoxic drugs.
Adverse Reactions - Common
- Gastrointestinal upset (dyspepsia, diarrhea) (Common)
- Headache (Common)
- Dizziness (Common)
Adverse Reactions - Serious
- Hepatotoxicity (liver failure) (Rare, but potentially serious)
- Stevens-Johnson Syndrome or Toxic Epidermal Necrolysis (Rare)
Drug-Drug Interactions
- CYP2C9 inhibitors or inducers may alter levels of terbinafine.
Drug-Food Interactions
N/ADrug-Herb Interactions
N/ANursing Implications
Assessment: Baseline liver function tests, renal function, and skin assessment.
Diagnoses:
- Risk for hepatotoxicity
- Impaired skin integrity
Implementation: Monitor liver enzymes periodically during therapy.
Evaluation: Assess for resolution of fungal infection and monitor for adverse effects.
Patient/Family Teaching
- Take medication with food to reduce gastrointestinal upset.
- Report signs of liver problems (jaundice, dark urine, severe fatigue).
- Complete full course of therapy even if symptoms resolve.
- Avoid alcohol and hepatotoxic substances.
Special Considerations
Black Box Warnings:
- Hepatotoxicity is rare but serious; monitor liver function.
Genetic Factors: Genetic polymorphisms may affect metabolism, but not routinely tested.
Lab Test Interference: May slightly affect liver function tests.
Overdose Management
Signs/Symptoms: Nausea, vomiting, headache, dizziness, abdominal pain.
Treatment: Supportive care; no specific antidote. Hemodialysis not effective due to extensive tissue binding.
Storage and Handling
Storage: Store at room temperature, 20-25°C (68-77°F).
Stability: Stable under recommended storage conditions for the shelf life indicated.