Triamcinolone Acetonide
Triamcinolone acetonide is a synthetic, intermediate-acting **glucocorticoid** that is approximately 4 to 10 times (and up to 40 times in some models) more potent than hydrocortisone. **Clinical Pearls & Key Features:** * **Zero Mineralocorticoid Activity:** Unlike hydrocortisone or prednisone, triamcinolone lacks appreciable mineralocorticoid effects, meaning it does not cause significant sodium or water retention. * **Versatile Administration:** It is utilized systemically (oral, injectable), topically, intra-articularly (especially in equine sports medicine), and intralesionally (e.g., for esophageal strictures or lick granulomas). * **Duration of Action:** When given orally, its metabolic activity lasts 24-48 hours. However, intramuscular (IM) or subcutaneous (SC) depot injections can persist for 4 to 6 weeks (sometimes up to 8 weeks), making it useful for chronic inflammatory or allergic conditions where daily pilling is difficult, though this increases the risk of prolonged adrenal suppression. * **Equine Use:** Frequently used for intra-articular injections in high-motion joints to reduce synovitis and improve lameness. It is an ARCI Class 4 drug in racing.
Mechanism: Triamcinolone exerts its effects via classic genomic and non-genomic glucocorticoid pathways: 1. **Genomic Pathway:** Free triamcinolone crosses the cell membrane and binds to the cytosolic **glucocorticoid receptor (GR)**. 2. The receptor-ligand complex translocates to the nucleus and binds to **Glucocorticoid Response Elements (GREs)** on DNA. 3. **Anti-inflammatory Protein Induction:** It upregulates the expression of **lipocortin-1 (annexin A1)**. Lipocortin-1 inhibits **phospholipase A2**, thereby blocking the release of arachidonic acid from membrane phospholipids. 4. **Eicosanoid Suppression:** This โ halts the synthesis of pro-inflammatory prostaglandins and leukotrienes (via COX and LOX pathways). 5. **Cytokine Inhibition:** It suppresses the transcription of major inflammatory cytokines (e.g., IL-1, IL-6, TNF-ฮฑ) and reduces inflammatory cell migration and capillary permeability.
Dosing by species
- Glucocorticoid effects ยท 0.25-0.5 mg PO once daily for 7 days ยท PO ยท q24h ยท 7 days
- Pododermatitis, feline plasmacytic pharyngitis ยท 2-4 mg (total dose) PO once a day or every other day 0.4-0.6 mg/kg PO once daily, then taper. ยท PO ยท q24h or q48h ยท Tapered
- Pemphigus complex ยท 0.4-0.8 mg/kg/day PO ยท PO ยท q24h
- General therapy (Tablets) ยท 0.11 mg/kg PO initially once a day, may increase to 0.22 mg/kg PO once daily if initial response is unsatisfactory. As soon as possible, but not later than 2 weeks, reduce dose gradually to 0.028-0.055 mg/kg/day ยท PO ยท q24h ยท Taper within 2 weeks
- Inflammatory, allergic, or dermatological disorders (Injectable) ยท 0.11-0.22 mg/kg for inflammatory or allergic disorders, and 0.22 mg/kg for dermatological disorders. ยท IM/SC ยท As needed ยท Effects generally persist for 7-15 days ยท If symptoms recur, may repeat or institute oral therapy.
- Intralesional injection ยท Usual dose is 1.2-1.8 mg; inject around lesion at 0.5-2.5 cm intervals. Do not exceed 0.6 mg at any one site or 6 mg total dose. ยท Intralesional ยท As needed ยท May repeat as necessary.
- To prevent re-stricture after esophageal dilation ยท Using an endoscopically directed needle, inject 0.5-1 mL of Vetalog (2 mg/mL) submucosally at time of dilation procedure. Infiltration is done circumferentially at four points around the site. ยท Submucosal ยท Once at time of procedure
- Adjunctive treatment of miliary dermatitis ยท 0.2-0.6 mg/kg PO once daily for 10-14 days, then tapered. ยท PO ยท q24h ยท 10-14 days, then taper
Routes of administration
Contraindications
- Systemic fungal infections
- Viral infections
- Active tuberculosis
- Peptic ulcers
- Corneal ulcers
- Acute psychoses
- Cushingoid syndrome
- Idiopathic thrombocytopenia (IM administration)
- Hypersensitivity to the drug
Adverse effects
- Polyuria (PU)
- Polydipsia (PD)
- Polyphagia (PP)
- Weight gain
- Panting (dogs)
- Dull, dry haircoat
- Vomiting and diarrhea
- Elevated liver enzymes (e.g., ALP)
- Pancreatitis
- Gastrointestinal ulceration
- Lipidemias
- Insulin resistance / Activation of diabetes mellitus
- Muscle wasting
- Behavioral changes (depression, lethargy, viciousness)
- Iatrogenic hyperadrenocorticism (Cushing's syndrome) with chronic use
- Laminitis (horses)
Drug interactions
- Amphotericin B ยท May cause hypokalemia when administered concomitantly
- Opiate Analgesics / Local Anesthetics (Epidural) ยท Combination in epidurals has caused serious CNS injuries and death; restrict volume to very small intrathecal test doses
- Anticholinesterase Agents (e.g., pyridostigmine) ยท May lead to profound muscle weakness in myasthenia gravis patients; discontinue 24h prior if possible
- Aspirin ยท Glucocorticoids may reduce salicylate blood levels
- Barbiturates ยท May increase the metabolism of glucocorticoids and decrease blood levels
- Cyclophosphamide ยท Glucocorticoids may inhibit hepatic metabolism of cyclophosphamide; dosage adjustments may be required
- Cyclosporine ยท May mutually inhibit hepatic metabolism, increasing blood levels of both drugs
- Potassium-depleting Diuretics (e.g., spironolactone) ยท May cause hypokalemia
- Erythromycin, Clarithromycin ยท May increase triamcinolone levels
- Estrogens ยท May potentiate the effects of triamcinolone
- Insulin ยท Insulin requirements may increase due to glucocorticoid-induced insulin resistance
- Isoniazid ยท Triamcinolone may decrease isoniazid levels
Monitoring
- Weight, appetite, signs of edema
- Serum and/or urine electrolytes
- Total plasma proteins, albumin
- Blood glucose
- Growth and development in young animals
- ACTH stimulation test if necessary
Overdose
Short-term administration of massive doses is unlikely to cause harmful effects, though one case of acute CNS effects in a dog after accidental ingestion has been reported. If acute clinical signs occur, provide supportive treatment. **Chronic Toxicity:** Chronic overdosage or prolonged use leads to serious adverse effects, primarily manifesting as iatrogenic hyperadrenocorticism (Cushing's syndrome), immunosuppression, and adrenal axis suppression.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerโs current label.