Are there any incompatibilities in next preparation? Hydroxypropylmethylcellulose 6000 3g Glycerin 6g Diphenhydramine HCl 250mg Lidocaine HCl 2g Susp Mg trisilicate et

The suspension Mg Trisilicate and CaCO3 has the cellulose dispersion as a viscosities increase (also contains a small amount of NaCMC) and the mucus solution with NaCMC. An incompatibility with diphenhydramine HCl and lidocaineHCl can be expected, although the presence of nacitrate will reduce the interaction to some extent by the conversion of both salts into their base form. There are two possible solutions. The first consists in increasing the amount of citrate. Here is a bit of calculating work because the amount required for 2 G lidocaineHCl should be calculated; 250 mg Diphenhydraminehcl may be neglected. The second solution consists in the preparation of the suspension from NF VI without the two thickening agents mentioned. I suspect that 3 G HPMC 6000 will give a sufficient viscosity.

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In the reactions + load with-load makes lidocaine apparently an exception (see question about "combination of Chlorhexidinedigluc. and Nystatin suspension) but this does not apply to Diphenhydramineh +. If there is a negatively charged polymer in the suspension mgtrisilicate and calcium carbonate NF VI, then clumping may occur. The added nacitrate (750 mg/300 ml) may prevent this. But both diphenhydramine and lidocaine will react with nacitate and given the large amount of Lidocasein HCL the 750 mg will be insufficient. I would therefore suggest both the cellulose dispersion and the CMC-mucus solution to be omitted from the composition and to prepare the suspension with the prescribed HPMC.