Comparison of Tear Sampling Techniques for Pharmacokinetic Analysis: Ofloxacin Concentrations in Rabbit Tears after Sampling with Schirmer Tear Strips, Capillary Tubes, or Surgical Sponges

Abstract

This study compared the precision and accuracy of 4 tear sampling methods. In vivo, albino rabbits were treated with single bilateral eye drops ofofloxacin 0.3% solution, 3 hr after which tear samples were collected using capillary tubes (CT), surgical sponges (SS), or tear strips for 15 sec (15sTS) or 60 sec (60sTS). In vitro, CT, SS, and tear strips were spiked with known volumes of ofloxacin solution in order to assess the bioanalytical accuracy of each technique. Ofloxacin levels were quantified by HPLC in all samples. Results showed that tear volumes and ofloxacin masses sampled in vivo depended on sampling method. Tear volume followed the rank order 60sTS > 15sTS > SS > CT. The volume collected by 60sTS exceeded precorneal tear volume. Ofloxacin mass followed the order 60sTS approximately 15sTS > SS > CT. Tear concentrations (mean +/- SD; N = 12) were 3.28 +/- 3.76 microg/g for 60sTS, 10.3 +/- 10.0 microg/g for 15sTS, 9.75 +/- 8.04 microg/g for SS, and 5.83 +/- 3.35 microg/g for CT. In vitro, SS, 15sTS, and 60sTS yielded accuracies of 103-107% and coefficients of variation (CV) < 9%. CT was only 85% accurate with a CV of 31%, indicating incomplete extraction during analysis. We concluded from this study that: 1) rabbit tear sampling by SS was rapid, easy, accurate, precise, and easily analyzable; 2) sampling by CT or 15sTS was accurate, but may require aggressive extraction (for CT) or be affected by tear flow rate (for 15sTS); and 3) tear sampling by 60sTS underestimated actual tear concentrations.

Dual-Drug Delivery System Based on In Situ Gel-Forming Nanosuspension of Forskolin to Enhance Antiglaucoma Efficacy

“…Noninvasive method based on tears sampling (29) followed by HPLC analysis was used for the study. Tear samples equivalent to 1 µl were collected from the right eye after application of test delivery system at 0, 0.017, 0.083, 0.5, 1, 2, 3, 4, 5, and 6 h postdosing.…”

Lachrymal Determinations: Methods and Updates on Biopharmaceutical and Clinical Applications

“…(a) chemical stimuli: gas like bromacetone [6,34], fumes (or vapor) of liquid agents like ethanol, formalin or ammonium [3,35,36] or cigarette fumes [37]; (b) physical stimuli: intensive light [38], mechanical stimuli by means of gentle aggression on the cornea (puff of air, fine brush, little sponge placed against the lower fornix) [15,37,39,40,41] and (c) physiological stimuli: the tearing reflex can be induced by a sneezing or yawning stimulation, which presents the great advantage of not altering ocular structures [14,42,43].…”

“…This solvent (the liquid receiver) can be frozen before analytical determination. Besides Schirmer strips, other absorbing supports have been proposed: (a) filter paper discs that are applied to perform MIC determination (antibiogram) [38,54], (b) sponges that present the great asset to significantly increase absorption capacity compared to classic strips (up to 5/6 times); release is easily obtained after agitation [25,40] and, like with cellulose strips after sonic agitation, occurs without degradation and (c) swabs recommended for virus detection (e.g. herpes virus simplex), which are directly placed in cellular cultures [55].…”

“…Yield coefficients have been calculated to ensure the absence of retention (irreversible or strong absorption or adsorption). This verification has been carried out only by a few authors, with endogenous components like IgE [25] or pharmacological agents (an analgesic agent [58] or ofloxacin [40]). …”

“…Direct Sampling Glass microcapillary tubes are directly used to sample tear fluid by capillarity [5,6,23,25,26,29,30,31,33,34,40,43,50,51,52,54,61,63]. The sampling procedure has been very precisely described (specifying position and corresponding gestures of the operator) and must respect strict supervisions in order to avoid any direct contact with ocular tissue or accidental puncture [62].…”