Clarithromycin → 4-oxo-4-[[(2R)-2,5,7,8-tetramethyl-2-(4,8,10-trimethylundecyl)-3,4-dihydrochromen-6-yl]oxy]butanoic acid

Participants

Reaction Steps

Clarithromycin was obtained as the free base from Wockhardt (Delhi, India). Vitamin E Succinate (VESA) was obtained from Eastman (Freeport Tenn.). Capmul® MCM was obtained from Abitec (Janesville Wis.); Poloxamer® 407 (Pluronic® F-127) from BASF (Parsippany N.J.); PEG-400 from Spectrum Chemicals (Gardenia Calif.), and d-δ-tocopherol from Sigma Chemicals (St Louis MO). An oil phase consisting of d-δ-tocopherol and Capmul MCM was prepared using 2 parts of δ-tocopherol. Surfactant and clarithromycin were then added as shown in the table below. Dry ethanol was used to dissolve the components at 70° C. and the ethanol was then removed under vacuum. A clear amber oil resulted, but upon cooling, oblong, “casket-lid” crystals of clarithromycin were observed. A tocol-soluble ion pair of this compound was then produced by addition of a stoichiometric equivalent of Vitamin E succinate (VESA) as the free acid. On re-dissolution in ethanol and cooling no crystals formed. The clarithromycin was now sufficiently soluble in the tocopherol oil to allow subsequent preparation of the emulsion. The oil was then re-heated to 45° C. and degassed immediately prior to emulsification as described below.

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