Controlled drug delivery devices for experimental ocular studies with timolol 2. Ocular and systemic absorption in rabbits

Efficacy of Antibody Delivery to the Retina and Optic Nerve by Topical Administration

“…Similar reductions were reported following topical application of antibodies in the rabbit. 38 Thus, high concentrations would have to be applied to get potentially therapeutic levels into the retina; interestingly, our bioassay results suggest this can be achieved, since the concentrations of antibody that we applied to the surface of rat eyes were similar to the concentrations of stock solutions of Avastin and Lucentis used for the treatment in humans. 7 Another potential advantage of topical administration of anti-VEGF is its decreased accumulation in the systemic circulation.…”

Thiolated poly(aspartic acid) as potential in situ gelling, ocular mucoadhesive drug delivery system

“…The conjunctiva is the major site of systemic absorption which also plays an important role in drug elimination from the ocular surface thanks to its rich blood flow, large surface area and more permeable membrane compared to the corneal membrane. There is therefore a need for the frequent instillation of eye drops, which is accompanied by discomfort and a decrease in patient compliance, especially in long-term therapy (Urtti et al, 1990;Urtti and Salminen, 1993;Ludwig, 2005;Junginger et al, 2002;Pepić et al, 2013).…”

Undefined role of mucus as a barrier in ocular drug delivery

“…The rate of drug elim- 55 ination from the tear fluid is in the range of 0.5-1.0 min À1 , and it 56 has been shown that the drug absorption takes place during the 57 first 2-3 min after instillation [5][6][7]. However, the ocular bioavail- 58 ability is low; usually in the range of 0.1-5% [8,9]. This is due to the 59 ocular permeation barriers and short contact time that limits the 60 period that is available for drug absorption [8].…”

“…Systemic 63 absorption from the conjunctival sac is an order of magnitude 64 faster than ocular absorption [11]. For example, timolol has 65 bioavailability of 4% in rabbit eyes, whereas the systemic 66 bioavailability from eye drops is about 80% with peak concentra- 67 tion in plasma already at 3 min [9,13]. Role of mucins located on 68 the ocular surface and in the tear fluid should be evaluated in this 69 context.…”