普遍认为眼药水的生物利用度(Bioavailability)是相当低的,对绝大多数药物来讲,滴入眼内的剂量只有少于1%的量通过角膜到达前房。眼结膜囊的容纳液体量是有限的,我国人结膜囊药容量一般在20微升以下。滴量在12微升时,约有半数人会溢出,滴量为16微升时71.4%会溢出,滴量为20微升时90.9%会溢出,滴量达24微升时基本上全部人都会溢出。一滴眼药液约50～60微升,因此,滴眼后大部份流失,滴入的部份经泪液稀释后又有部份经鼻泪管流入鼻腔,因而只有极小量的药物才起到真正的治疗作用。从制剂的角度考虑,眼内药物的吸收,其关键在于作用部位或吸收部位药液贮藏的多少及药物与吸收部位接触时间的长短。由于结膜囊的容量是一定值,滴入过量的药液会造成浪费,故有人提出,眼药水的用量从目前50～60微升减少到5～10或10～20微升,可得到最合适的利用度。但这样小的微滴,给药时易使药液落在眼帘外或眼睫毛上,所以这种方法在临床应用上意义并不很大。 It is generally accepted that the bioavailability of eye drops is rather low, and for most drugs, less than 1% of the dose dropped into the eye reaches the anterior chamber through the cornea. Ocular conjunctival sac to accommodate liquid volume is limited, the Chinese people conjunctival sac capacity is generally below 20 microliters. Approximately half of the spills will spill at 12 μl, 71.4% at 16 μl, 90.9% at 20 μl, and essentially all at 24 μl Will overflow. A drop of liquid about 50 to 60 microliters, therefore, after most of the loss of the eye drops, the part of the drop by the tear after dilution and part of the nasolacrimal duct into the nasal cavity, and thus only a very small amount of drug only To the real therapeutic effect. From the preparation point of view, the absorption of intraocular drugs, the key lies in the role of the site or part of the absorption of liquid storage and drug absorption and absorption of the site the length of time. As the capacity of the conjunctival sac is a certain value, dropping excess liquid will cause waste, it was suggested that the amount of eye drops from the current 50 to 60 microliters reduced to 5 to 10 or 10 to 20 microliters, the most suitable The degree of utilization. But such a small droplet, when administered easy to make the liquid fall on the eye or eyelashes, so this method in clinical significance is not significant.