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Editors Selection IGR 11-4

Medical Therapy: Microneedle drug delivery

Comment by George Lambrou on:

19607 Coated microneedles for drug delivery to the eye, Jiang J; Gill HS; Ghate D et al., Investigative Ophthalmology and Visual Science, 2007; 48: 4038-4043

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This is a pilot study on the feasibility of delivering low-molecular-weight drugs or biopharmaceuticals (proteins and genetic material) into the eye via microneedles. Jiang et al. (1092) inserted (for 20-120 sec) non-penetrating steel needles, 500-750 m long and 50x200 m in cross-section, that pierce but not fully traverse the ocular tunics and that were previously dipped into the active compound to be delivered. Their data suggest that the compound diffuses quickly from the microneedle into the surrounding ocular tunic (they used human cadaver scleras and rabbit corneas in vivo) where it forms a depot, from which it is then delivered into the intraocular tissues and fluids over several hours. Having observed traces of abrasions lasting no more than three hours at the delivery site, and at no time any signs of ocular inflammation, nor any other adverse effects, the authors suggest that microneedle insertion is well-tolerated, although they acknowledge that further studies are required to fully assess safety of the procedure.

Avoiding intravitreal injections for drug delivery to the posterior segment may reduce significantly the risk of serious complications; drug delivery via micro needles may be carried out by non-retinal specialists

The benefits of this approach are different for the intracorneal and intrascleral routes. Following intracorneal delivery, the data point to a 50- to 70-fold increase of drug bioavailability in the anterior chamber, while diffusion of the drug into the tear film and the ensuing systemic exposure are minimized. Following intrascleral delivery of drugs targeting posterior segment tissues, improvements in bioavailability over intravitreal injections are unlikely, but avoiding the latter may reduce significantly the risk of serious complications and may permit the procedure to be carried out by non-retinal specialists. What is the relevance of this to glaucoma? It is highly unlikely that the daily topical administration of small-molecule eyedrops for POAG will be replaced any day soon by an invasive approach, however minimal the invasion. On the other hand, the development of biopharmaceuticals, such as siRNA, or certain specific forms of glaucoma (like neovascular glaucoma) may well benefit from new delivery technologies - of which the microneedles are an example - if they prove to be efficacious in terms of drug bioavailability and safe for routine use.

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