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Ocular pharmacokinetics of calcium, chloride and sulphate ions after instillation in the rabbit
Author(s) -
Hariton C.,
Mandel P.
Publication year - 1991
Publication title -
biopharmaceutics and drug disposition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.419
H-Index - 58
eISSN - 1099-081X
pISSN - 0142-2782
DOI - 10.1002/bdd.2510120602
Subject(s) - cornea , chloride , calcium , chemistry , benzalkonium chloride , pharmacokinetics , penetration (warfare) , lens (geology) , chromatography , ophthalmology , pharmacology , medicine , biology , paleontology , organic chemistry , operations research , engineering
The ionic environment of the eye is involved in major biochemical processes which are essential for preserving the integrity of cornea and lens. The purpose of the present study was to determine the intra ‐ocular penetration and the pharmacokinetic parameters of calcium, chloride and sulphate ions in the cornea, iris‐ciliary body (ICB) and lens, after administration by instillation in the rabbit eye. In order to extrapolate our results to the processes occurring in man, we followed a precise instillation protocol using a low volume (5 μl) of 45 Calcium, 36 Chloride and 35 Sulphate, which is less than the lacrimal volume determined during the palpebral closing and performing manual blinking at a frequency of 2 min −1 The results indicate an immediate trans ‐corneal permeability and a rapid ocular distribution of these ions. We observe that, relative to dose, an important percentage of calcium (67·20 per cent) was entrapped in the cornea; this parameter was less important for chloride (10·19 per cent) and for sulphate ions (3·25 per cent). These values are in agreement with those predicted theoretically for trans ‐corneal penetration by such compounds. On the other hand, the total degrees of penetration by chloride and sulphate ions in ICB (1·40 per cent and 0·90 per cent, respectively) and lens (0·35 per cent and 0·41 per cent, respectively) are quite similar. Calcium retention is much higher in these tissues (25·39 per cent in ICB and 16·03 per cent in lens). It seems likely that the higher degree of lens entrapment of calcium may be explained by the trans ‐capsular electrical potential difference and the negative charge inside the lens and the presence of proteins possessing high affinity and binding capacity for calcium.