Source: FDA, National Drug Code (US) Revision Year: 2020
Atropine acts as a competitive antagonist of the parasympathetic (and sympathetic) acetylcholine muscarinic receptors. Topical atropine on the eye induces mydriasis by inhibiting contraction of the circular pupillary sphincter muscle normally stimulated by acetylcholine. This inhibition allows the countering radial pupillary dilator muscle to contract which results in dilation of the pupil. Additionally, atropine induces cycloplegia by paralysis of the ciliary muscle which controls accommodation while viewing objects.
The onset of action after administration of ISOPTO Atropine 1% generally occurs in minutes with maximal effect seen in hours and the effect can last multiple days [see Clinical Studies (14)].
In a study of healthy subjects, after topical ocular administration of 30 µL of atropine sulfate ophthalmic solution, 1%, the mean (± SD) systemic bioavailability of l-hyoscyamine was reported to be approximately 64 ± 29% (range 19% to 95%) as compared to intravenous administration of atropine sulfate. The mean (± SD) time to maximum plasma concentration (Tmax) was approximately 28 ± 27 minutes (range 3 to 60 minutes), and the mean (±SD) peak plasma concentration (Cmax) of l-hyoscyamine was 288 ± 73 pg/mL. The mean (±SD) plasma half-life was reported to be approximately 2.5 ± 0.8 hours.
In a separate study of patients undergoing ocular surgery, after topical ocular administration of 40 µL of atropine sulfate ophthalmic solution, 1%, the mean (± SD) plasma Cmax of l‑hyoscyamine was 860 ± 402 pg/mL.
Atropine sulfate was negative in the Salmonella/microsome mutagenicity test. Studies to evaluate carcinogenicity and impairment of fertility have not been conducted.
Topical administration of ISOPTO Atropine 1% results in mydriasis and/or cycloplegia, with efficacy demonstrated in both adults and children. The maximum effect for mydriasis is achieved in about 30–40 minutes after administration, with recovery after approximately 7–10 days. The maximum effect for cycloplegia is achieved within 60–180 minutes after administration, with recovery after approximately 7–12 days.
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