Kenalog-40
Kenalog‑40
Generic Name
Kenalog‑40
Mechanism
- Glucocorticoid receptor (GR) binding: Triamcinolone acetonide enters cells, translocates to the nucleus, and binds the GR.
- Transrepression: GR complexes inhibit NF‑κB, AP‑1, and other transcription factors → ↓ cytokine, chemokine, phospholipase A2.
- Transactivation: Up‑regulation of anti‑inflammatory proteins such as lipocortin‑1 (annexin‑1) → ↓ leukotriene synthesis.
- Result: Rapid suppression of local inflammation, edema, and pain in joints or soft‑tissue structures.
---
Pharmacokinetics
| Parameter | Detail |
| Absorption | IM and intra‑articular injections exhibit a *slow, depot‑based release*; peak plasma concentrations reach 2–4 weeks post‑injection. |
| Distribution | Large volume of distribution (≈ 1 L/kg) due to high lipophilicity; extensive tissue binding. |
| Metabolism | Hepatic glucuronidation and oxidation; minimal urinary excretion of unchanged drug. |
| Half‑life | Apparent elimination half‑life ≈ 12–24 h; clinical effect persists for weeks because of depot action. |
| Protein binding | > 90 % bound to albumin. |
| Drug interactions | CYP3A4 inducers (e.g., rifampin) may accelerate clearance; avoid co‑administration with potent CYP3A4 inhibitors if systemic exposure is a concern. |
--
•
Indications
- Osteoarthritis of knee, shoulder, hip, and hand joints
- Rheumatoid arthritis flares
- Gout and pseudogout intra‑articular control
- Temporomandibular joint (TMJ) dysfunction
- Bursitis (supraspinatus/biceps, olecranon, patellar)
- Inflammatory arthropathies (ankylosing spondylitis, psoriatic arthritis)
- Soft‑tissue lesions (intra‑lesional injection for nodules, cysts)
---
Contraindications
| Contraindication | Warning |
| Active systemic infection | Diabetes mellitus – monitor glucose; may worsen hyperglycemia. |
| Known hypersensitivity to triamcinolone or excipients | Hypertension – careful blood‑pressure monitoring. |
| Uncontrolled glaucoma (if intra‑ocular use) | Post‑treatment adrenal suppression – monitor for signs of Cushingoid features. |
| Severe osteoporosis & fracture risk | Pregnancy – category C; avoid during 1st trimester unless benefits outweigh risks. |
| Untreated systemic fungal infections | Elderly/immune‑suppressed patients – heightened infection risk. |
--
•
Dosing
- Joint injections
- *Knee*: 40 mg (1 mL)
- *Shoulder*: 20 mg (0.5 mL)
- *Wrist/hand*: 10 mg (0.25 mL)
- *TMJ*: 10 mg (0.25 mL) in the joint space
- Intramuscular (rarely used for systemic inflammation): 40 mg IM in gluteus medius/semitendinosus, respecting sterile technique.
- Maximum: 80 mg per joint per 1‑month interval; never exceed cumulative joint dose of 80 mg per month to reduce cartilage degeneration risk.
- Technique:
- Aspirate intra‑articular space to avoid intra‑vascular injection.
- Use a 23–25 G needle for small joints; 22 G for larger joints.
- Add 0.2 mL of lidocaine (1–2%) only for painful injections—helps mitigate injection pain without diluting steroid dose.
---
Adverse Effects
| Category | Typical Examples |
| Local | Injection‑site pain, bruising, arthralgia, transient swelling, aseptic pseudoparalysis (rare). |
| Systemic (rare) | Hyperglycemia, hypertension, mood swings, adrenal suppression, Cushingoid features. |
| Serious | Osteonecrosis of the femoral head (high cumulative doses), severe hypotension (intra‑vascular administration), ocular hypertension (if intra‑ocular). |
--
•
Monitoring
| Test | Frequency | Rationale |
| Blood glucose & HbA1c | Baseline, 1 mo, 3 mo | Detect steroid‑induced hyperglycemia. |
| Blood pressure | Every visit | Corticosteroid‑mediated hypertension. |
| Bone densitometry | Baseline, 6 mo (for long‑term users) | Assess risk of systemic bone loss. |
| Joint assessment | Before each injection | Document baseline pain, ROM for efficacy comparison. |
| Serology (if patient on immunosuppressants) | As clinically indicated | Monitor for opportunistic infections. |
--
•
Clinical Pearls
1. Depot Advantage: The slow release of Kenalog‑40 from synovial cartilage gives 4–6 week symptomatic relief – ideal for patients on oral NSAIDs or those needing intermittent injections.
2. Limit Joint Frequency: Re‑injecting the same joint more than once every 6–8 weeks significantly increases cartilage damage risk. Use the 80 mg/month rule strictly.
3. Avoid Intravascular Injections: Always aspirate before injection; if blood is aspirated, relocate the needle. Intravenous exposure can lead to systemic hypertension.
4. Use With NSAIDs or COX‑2 Inhibitors? Peri‑injection NSAIDs provide added analgesia, but avoid concurrent systemic steroids to reduce adrenal suppression.
5. Pregnancy Caution: While Kenalog‑40 is Category C, short‑term, single‑joint injections can be considered under specialist guidance if anti‑inflammatory benefit outweighs fetal risk.
6. Cartilage Toxicity Evidence: In vitro studies reveal that high steroid concentrations (> 200 µg/mL) can decrease chondrocyte viability; hence, careful dosing and minimal cumulative exposure are key.
7. Injectable Formulation Clarification: Kenalog‑40 *is not fluticasone*—it’s triamcinolone acetonide. Confusing with fluticasone nebulizer solutions can result in dosage errors; always double‑check vial labels.
8. Post‑Injection Rehab: Gentle ROM exercises after 1–2 days prevent stiffness and improve joint function without compromising steroid efficacy.
9. Adrenal Suppression Screening: In patients with longstanding steroid use, perform a short Synacthen test if they exhibit fatigue or hypotension.
10. Patient Education: Explain the *delayed peak effect* (up to a month) and advise rest for 48–72 h post‑injection to allow depot formation.
--
• *References:*
• Goodman & Gilman’s *The Pharmacological Basis of Therapeutics*.
• FDA prescribing information, Kenalog‑40.
• American College of Rheumatology guidelines on intra‑articular steroid injections.