(fye'' soe stig' meen sul' fate).
Pyrrolo[2,3-b]indol-5-ol, 1,2,3,3a,8,8a-hexahydro-1,3a,8-trimethyl-, methylcarbamate (ester), (3aS-cis)-, sulfate (2:1).
Physostigmine sulfate (2:1) [64-47-1].
» Physostigmine Sulfate contains not less than 97.0 percent and not more than 102.0 percent of (C15H21N3O2)2·H2SO4, calculated on the dried basis.
Packaging and storage Preserve in tight, light-resistant containers.
USP Reference standards 11
B: A solution (1 in 100) responds to the tests for Sulfate 191.
Specific rotation 781S: between 116 and 120.
Test solution: 10 mg per mL, in water.
Loss on drying 731 Dry it at 105 to constant weight: it loses not more than 1.0% of its weight.
Residue on ignition 281: negligible, from 100 mg.
Readily carbonizable substances 271 Dissolve 100 mg in 5 mL of sulfuric acid: at the end of 5 minutes the solution has no more color than Matching Fluid I.
Assay Dissolve about 200 mg of Physostigmine Sulfate, accurately weighed, in 25 mL of water. Render the solution alkaline by the addition of about 1 g of sodium bicarbonate, and extract with one 25-mL and five 10-mL portions of chloroform, each time shaking vigorously for 1 minute. Filter each extract through glass wool. Add 15 mL of glacial acetic acid and 10 mL of acetic acid anhydride to the combined chloroform extracts, and titrate with 0.02 N perchloric acid VS, determining the endpoint potentiometrically. Perform a blank determination, and make any necessary correction. Each mL of 0.02 N perchloric acid is equivalent to 6.488 mg of (C15H21N3O2)2·H2SO4.
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USP35NF30 Page 4317Pharmacopeial Forum: Volume No. 34(5) Page 1179