Retrobulbar administration route

Periocular steroids can be administered by subconjimcti-val, sub-Tenon s capsule, or retrobulbar injection. A topical anesthetic often is instilled before the steroid is injected. This route of administration can be effective during surgical procedures, as a supplement to topical and systemic steroids in cases of severe inflammation, and in patients not compliant with the prescribed regimen. 

Classical pharmacokinetic models of systemicaUy administered drugs (see Chapter 1) do not fuUy apply to many ophthalmic drugs. Most ophthalmic medications are formulated to be apphed topically or may be injected by subconjunctival, sub-Tenon s, and retrobulbar routes (Figure 63-1 and Table 63-1). Although similar principles of absorption, distribution, metabolism, and excretion determine drug disposition in the eye, these alternative routes of drug administration introduce other variables in compartmental analysis. 

Parenteral and topical routes of administration maximum single dose for an average 70 kg adult is 175 mg. Local infiltration 0.25-0.75%, peripheral nerve block 0.25% and 0.5%, retrobulbar block 0.75% (15-30 mg), and sympathetic block 0.25% (50-125 mg). 

Among the novel routes, subconjimctival injection allows circumvention of the barriers imposed by cornea and conjunctiva, resulting in higher levels in vitreous. The sub-tenon route is a good alternative to retrobulbar and peribulbar ones for administration of anesthesia due to less complications and avoidance of sharp needles. 

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