Betamethasone
**Betamethasone** is a potent, long-acting glucocorticoid used in veterinary medicine primarily for its profound anti-inflammatory and immunosuppressive effects. In ophthalmic applications, it was formerly available as a veterinary-approved antimicrobial-steroid combination (Gentocin Durafilm®). While commercial veterinary ophthalmic products containing betamethasone are currently discontinued, compounding pharmacists can still provide preparations combining gentamicin and betamethasone for specific clinical needs.
Mechanism: Betamethasone diffuses across cell membranes and binds to specific cytosolic **glucocorticoid receptors**. The receptor-ligand complex translocates to the nucleus, where it alters gene expression (transactivation and transrepression). → **Inhibits phospholipase A2** (via lipocortin induction), blocking the release of arachidonic acid. → **Decreases production of inflammatory mediators** (prostaglandins, leukotrienes, cytokines). → **Suppresses immune system response** by reducing leukocyte migration and capillary permeability.
Routes of administration
Contraindications
- Suspected corneal abrasion
- Corneal ulceration
- Feline herpes keratitis (FHV-1)
Adverse effects
- Delayed corneal healing
- Increased intraocular pressure (IOP)
- Potentiation of ocular infections
- Systemic absorption leading to adrenal suppression (rare with topical use but possible in small patients)
Drug interactions
- NSAIDs · Increased risk of GI ulceration · major
- Insulin · Glucocorticoids antagonize the effect of insulin · major
- Phenobarbital · May accelerate the metabolism of corticosteroids · moderate
- Itraconazole · May decrease the metabolism of corticosteroids · moderate
- Acetazolamide · Increased risk of hypokalaemia · moderate
- Amphotericin · Increased risk of hypokalaemia · moderate
- Furosemide · Increased risk of hypokalaemia · moderate
- Thiazide diuretics · Increased risk of hypokalaemia · moderate
Monitoring
- Fluorescein staining (to ensure intact cornea prior to and during use)
- Intraocular pressure (IOP)
- Resolution of clinical signs of inflammation
Overdose
Overdose via topical ophthalmic administration is unlikely to cause acute life-threatening signs, but chronic overuse can lead to iatrogenic hyperadrenocorticism (Cushing's syndrome) and local ocular complications (glaucoma, corneal degeneration).
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.