pH of different syrup

What pH range for Multivitamin syrup, Herbal Antacid syrup, White Antacid syrup, Iron syrup, Calcium Syrup and IVY cough syrup

A calcium carbonate aqueous antacid suspension for oral use having a pH of about 7.5 to about 8.7

The bases used as antacids range in pH from 8.5 to 10.5

The mean pH of the syrups ranges from 3.06 to 8.4. However, it depends on the stability of the medicament / active ingredients added to it.

Generally, plain syrup (like Sugar syrup IP is 66.7% sugar solution in water) does not require pH adjustment. Only medicated syrups require pH adjustment in the range of 3 to 6. This is because general medicaments (drugs) are stable in acidic pH. Hence, the pH of medicated syrups is adjusted to ensure the stability of drugs in syrup until the defined shelf life (expiry period).

For antacids like Aluminum hydroxide, Magnesium hydroxide the inherent pH of these drugs (salts) is alkaline, and hence medicated syrups containing these antacid drugs have a pH at the alkaline side (more than 8 to 10) to ensure the stability of formulations up to shelf life.

The pH range of multivitamin syrups can vary, but is usually maintained between 4 and 5 or 4 and 6.5.
A stable aqueous multivitamin composition comprising vitamin A, Vitamin D3, Thiamine (Vit. B1), Riboflavin (Vit. B2), Niacinamide, Pyridoxine HCl (Vit. B6), Ascorbic acid (Vit. C), Cyanocobalamin (vIT B12), and Pantothenamide.

However, in all the above examples, the pH must be decided based on the stability studies to ensure that all active ingredients / APIs added in syrup remain stable until its shelf life / expiry.