Biomedical subjects

S A Birss

Publications and source records attributed to S A Birss.

3 recordsLinked to original sources

PubMed1978

Ocular hypotensive efficacy of topical epinephrine in normotensive and hypertensive rabbits: continuous drug delivery vs eyedrops.

The ocular hypotensive efficacy of continuously delivered epinephrine is compared to that of pulsed doses provided by eyedrops in both normotensive and hypertensive rabbit eyes. In normotensive eyes, 2 microgram/hr and 4 microgram/hr epinephrine delivered into the tear film continuously for 12 hours reduces intraocular pressure as well as eyedrop pulses of 0.5% epinephrine hydrochloride or 2% epinephrine bitartrate (doses of 500 and 1100 microgram, respectively). Ocular hypertension induced by an intragastric water load in rabbits is significantly inhibited by continuous delivery of epinephrine at the rates of 3 or 6 microgram/hr, or by 2% epinephrine bitartrate (1% free base) eyedrops. Epinephrine delivered continuously at rates of 2-6 microgram/hr for 6 to 12 hours (12-72 microgram total) has hypotensive efficacy equivalent to 15 to 40 times as much epinephrine applied once in eyedrops. Epinephrine bitartrate eyedrops reduce tear film pH well below normal. Continuous delivery of epinephrine bitartrate does not reduce tear film pH below normal levels.

Administration, Topical↗

PubMed1976

Intermittent vs continuous steroid administration. Efficacy in experimental conjunctivitis.

The development of techniques for the continuous administration of drugs to the eye raises the question of whether a conjunctivitis can be controlled by continuous low rates of steroid release, or whether large, intermittent doses of steroid, as provided by eyedrops, are necessary. Efficacy of the two modes of drug administration was evaluated in a conjunctivitis model produced in immunized rabbits by daily topical ocular challenge with antigen. The acetates of hydrocortisone and prednisolone were released from a drug delivery system inserted in the cul-de-sac of the eye or were provided in eyedrops. The model was sufficiently sensitive to differentiate between the effectiveness of hydrocortisone and prednisolone. The continuous delivery of either steroid from the drug delivery system was as efficacious, or more so, than the corresponding steroid dose given as eyedrops.

Administration, Topical↗

PubMed1976

The relationship between hydrocortisone acetate distribution and efficacy in inflamed eyes: continuous vs intermittent delivery.

Hydrocortisone acetate was administered to rabbit eyes intermittently in 250mug doses (given twice daily or once hourly) or continuously at 10mug/hr from an experimental ocular therapeutic system. Tissue drug distribution was measured over a 1 to 4 day period in experimental conjunctivitis. Anti-inflammatory efficacy was evaluated over a 4 day period in the same model. Statistically significant improvement in inflammation was observed 48 hours after initiation of continuous delivery treatment and after 4 days of the twice daily eyedrop regimen. Drug uptake by ocular tissues correlated with drug efficacy. Continuous delivery at 10mug/hr produced conjunctival steriod concentrations exceeding 1mug/g during 8 through 24 hours of treatment, and average levels of 1mug/g from days 2 through 4. Conjunctival steroid concentations generally did not exceed 1mug/g in eyedrop treated eyes until the fourth treatment day, when their clinical improvement matched that observed in the continuously treated eyes.

Administration, Topical↗