Clindamycin phosphate topical solution, for external use, contains clindamycin phosphate at a concentration equivalent to 10 mg clindamycin per milliliter in a hydroalcoholic solution. Clindamycin phosphate is a water soluble ester of the semi-synthetic antibiotic produced by a 7(S)-chloro-substitution of the 7(R)-hydroxyl group of the parent antibiotic lincomycin.

http://www.accessdata.fda.gov/spl/data/df3fdd8e-0c49-47f6-a8...

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Note added at 50 mins (2016-12-30 17:26:18 GMT)
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Dihydrostreptomycin is a derivative and is used as an alternative to the parent antibiotic.

http://medical-dictionary.thefreedictionary.com/streptomycin

For most antibiotics, a defined exposure– toxicity relationship does not always exist. In these scenarios, one must make an empirical decision about how much accumulation (AUC24SS), and thus the theoretical amount of toxicity, is acceptable. Accumulation should be assessed at the CLCR level immediately prior to the dose adjustment threshold, because this is the point of maximum accumulation for the parent antibiotic regimen.

http://jac.oxfordjournals.org/content/65/11/2285.full.pdf


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Note added at 53 mins (2016-12-30 17:28:53 GMT)
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This approach allows the preparatively useful generation of a series of antibiotics with increased lipophilicity over that of the parent antibiotic.

http://pubs.rsc.org/en/content/articlehtml/2015/sc/c5sc02919...

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Note added at 1 day23 hrs (2017-01-01 15:45:34 GMT) Post-grading
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It's my pleasure. Happy New Year to you, too!