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Sanja Dragovic, Paul Bryar; Evaluation of Number and Volume of Individual Eye Drops In 2.5ml Travoprost 0.004% Bottle and Variation Between Five Subjects. Invest. Ophthalmol. Vis. Sci. 2011;52(14):241.
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To evaluate the mean number of drops per bottle and mean individual eye drop volume in a 2.5ml bottle of travoprost 0.004% and to compare the variability of these values between five different subjects.
Ten bottles of 2.5 ml travoprost 0.004% were evaluated in the hands of five healthy subjects. Using their dominant hand, subjects were instructed to expel one drop onto a weighing plate calibrated to 0.1 µg. The angle of the elbow and bottle were similar to self-administration of eye drops. The amount of each drop was measured, and the process repeated until the bottle was empty. The total number of drops per bottle was recorded. Bottle was recapped after every even numbered drop to simulate patient use of medication bilaterally. When the bottle was empty, the subject repeated the procedure with the non-dominant hand. Subjects were masked to all measurements.
Mean number of drops expelled per bottle ranged from 84 to 105 and the difference between subjects was found to be statistically significant (p<0.0024). Mean number of drops per bottle expelled by all subjects with dominant hand was 92.8 and with non-dominant hand was 93.2; the difference was not statistically significant (p=0.89). Overall mean volume of individual drops expelled per subject ranged from 24.5 µl to 28.9 µl; this difference was found to be statistically significant between the subjects (p<0.0001). Mean volume of individual drops per bottle expelled by all subjects with dominant hand was 27.7 µl and with non-dominant hand was 27.6 µl; this difference was not statistically significant (p=0.74). In four out of five subjects, there was no significant difference in number or volume of individual drops when they used their dominant or non-dominant hand.
Prostaglandin analogues such as travoprost are frequently the initial choice in glaucoma treatment. How long the bottle of medication lasts varies between patients, with some running out of medication within 2-3 weeks, others lasting more than a month. Currently there is little published data on the number of drops or mean individual eye drop volume in prostaglandin analogues. We found a statistically significant difference between number of drops per bottle and a statistically significant variability in the volume of drops expelled by each of the five subjects using 2.5ml bottle of travoprost 0.004%. Based on these results, the dose of medication administered and length of time a bottle lasts will vary between patients.
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