Dexamethasone, Prednisolone, Fluorometholone, Loteprednol

Ocular Immune Response Modulators

Topical glucocorticoids potently inhibit the ocular inflammatory cascade by binding to specific intracellular receptors, modulating the protein synthesis of dural mediators of inflammation. However, they are associated with severe risks of ocular hypertension and cataracts.

Mechanism

💊 Commercial Names

Maxidex, Pred Forte, FML Forte, Lotemax, Tobradex (coformulación dexametasona + tobramicina).

🔬 Pharmacological Group

Glucocorticoides sintéticos tópicos oftálmicos. Loteprednol (derivado de carbonato de éster blando).

🧪 Standard Presentations

Dexametasona fosfato sódico 0.1%, Prednisolona acetato 1.0% (suspensión), Fluorometolona alcohol 0.1%, Loteprednol etabonato 0.5%.

Mechanism of Action

Los corticoides tópicos atraviesan por difusión pasiva la membrana de las células inflamatorias oculares (macrófagos, neutrófilos, linfocitos) y se unen a su receptor citoplasmático específico (GR):

Transactivación de la Lipocortina-1 (Anexina-1): El complejo glucocorticoide-receptor activado se transloca al núcleo celular y se une a elementos de respuesta a glucocorticoides (GRE). Esto incrementa la transcripción de la Lipocortina-1, proteína que inhibe directamente a la enzima Fosfolipasa A₂ (PLA₂). Al bloquearse la PLA₂, se impide la liberación de ácido araquidónico desde los fosfolípidos de la membrana dural celular, deteniendo la síntesis de prostaglandinas (vía COX) y de leucotrienos (vía LOX) de forma simultánea.
Transrepresión del Factor de Transcripción NF-κB: El complejo GR activado bloquea la actividad celular del NF-κB y del AP-1, impidiendo la síntesis de citocinas inflamatorias (IL-1, IL-2, IL-6, TNF-α), de moléculas de adhesión endotelial (ICAM-1, VCAM-1) y la quimiotaxis leucocitaria local.
Corticoides "Blandos" o de Sitio Específico (Loteprednol, Fluorometolona): El etabonato de loteprednol se metaboliza enzimáticamente a nivel ocular de forma ultrarrápida a metabolitos inactivos derivados del ácido carboxílico tras unirse al GR. Esto reduce su penetración y persistencia en la malla trabecular y el cristalino, disminuyendo drásticamente la tasa de efectos adversos de PIO elevada y formación de cataratas en comparación con dexametasona o prednisolona.

Pharmacokinetics

Quantitative Ocular and Systemic Pharmacokinetics

Parameter	Prednisolone Acetate 1.0%	Dexamethasone Phosphate 0.1%	Loteprednol Etabonate 0.5%
Formulation and Solubility	Insoluble lipophilic suspension; requires vigorous prior stirring.	Aqueous neutral acidic water-soluble solution with easy penetration.	Soft lipophilic suspension to optimize surface retention.
Corneal Penetration	High stromal penetration thanks to the lipophilic acetate salt.	Intermediate stromal penetration; requires an intact epithelium.	Good epithelial penetration, rapid subsequent metabolism.
T_max in Aqueous Humor	30 - 45 minutes	30 - 60 minutes	30 - 45 minutes
Clearance and Half-Life	Eliminated by filtration of the aqueous. t_1/2 ≈ 30 min.	t_1/2 in aqueous ≈ 45 min. Biliary and urinary excretion.	Metabolism by tissue esterases to inactive metabolite. t_1/2 ≈ 15 min.

Glaucoma due to Corticosteroids and Cataracts: The Danger of Chronic Treatment

The uninterrupted use of powerful topical corticosteroids (especially dexamethasone and prednisolone) for more than 2 to 4 weeks can induce two serious ocular complications of silent course: 1) Corticonic (Steroridean) Glaucoma: Corticosteroids suppress the cellular enzymatic clearance in the trabecular meshwork of glycoproteins and polymeric glycosaminoglycans, and induce the myocilin protein expression. This promotes the accumulation of hydrophilic dural extracellular matrix that occludes the mesh, raising aqueous humor resistance and IOP in up to 30% of sensitive patients. 2) Posterior Subcapsular Cataracts: Alteration of sodium-potassium transport in the epithelial cells of the lens and collagen crystalline cells, inducing bilateral whitish opacities that are difficult to resolve non-surgically.

Security

Contraindications

Absolute: Keratitis due to Herpes Simplex Virus of active epithelial type (typical dendritic lesions - corticosteroids suppress the local immune cellular response, promoting uncontrolled replication of the virus and causing a giant corneal geographic lesion with a necrotic course or corneal dural perforation); active ocular bacterial, fungal or mycobacterial infections not adequately treated with microbial coverage.
Relative: Pre-existing primary open-angle glaucoma; unstable diabetes.

Adverse Effects (ADR)

Local Ocular: Elevation of IOP (steroid-induced ocular hypertension, dose-dependent); formation of posterior subcapsular cataracts; significant delay in corneal epithelial healing (inhibition of collagen synthesis and keratocyte mitosis); scleral perforation in eyes with pathological thinning (due to metalloproteinase induction); transient eyelid ptosis; Mild pupillary mydriasis.
Systemic: Rare with topical ocular use at correct doses. In low weight children or with extremely frequent doses, it can induce suppression of the hypothalamic-pituitary-adrenal axis of exogenous origin.

Drug Interactions

Anti-VEGF or Antiglaucomatous Agents: Topical corticosteroids can moderately attenuate some peripheral cellular repair effects of these agents or annul their ocular hypotensive efficacy by direct trabecular elevation.

Epistemis is educational review material. It is not a medical device, does not diagnose or prescribe treatment, and does not replace formal medical training, current clinical guidelines, or professional clinical judgment.

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System: Ophthalmology
Cluster: Ocular Immune Response Modulators

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