Hi Sundar Khadka , you may try 5% DMSO. Start adding the antibiotics in DMSO first, then make it with DI water. You can also use a higher concentration of DMSO if you are preparing a stock solution. Good luck.

A 4 mg/ml solution looks like a paste?

Seems more likely to me that you have done something wrong in your calculations.

Magnus Bertelsen :Let me correct and explain in details :

1. Oral gavage: 10 mg (=0.01g) of each antibiotic in 200 µL tap water/mouse

10 mg Ampicillin + 10 mg Metronidazole + 10 mg Neomycin sulfate + 10 mg Vancomycin in 200 µL tap water/mouse (10 mg /200 µL )

2. Antibiotics cocktail in tap water: 0.1% Ampicillin (1g/L=1mg/ml) + 0.1% Metronidazole (1g/L) + 0.1% Neomycin sulfate (1g/L) + 0.05% Vancomycin (0.5g/L)

In oral gavage, total amount is 40mg/200 µL and looks sediment/deposit.

Satwik Majumder : Thank you sir.

Some of the solvents are : 10mg/ml in water, 5% DMSO , ethanol, propylene glycol. I will try with those solvents.

Hi Sundar Khadka , water may not work. DMSO or ethanol should work. Make sure to vortex well and even sonication for few minutes help. Good luck.

Sundar Khadka

So if I am understanding you correctly for the oral gavage you are trying to do:

10mg of each antibiotic in 200 µl water = 10mg/200µl = 50mg/ml = 5% (x4)

From what I have found Metronidazole alone is only soluble at 10mg/ml in water or 34mg/ml in DMSO so already there you will start to run into problems.

If the 5% DMSO does not work you might want to play around with the pH as well, but in any case I think it will be difficult to fully dissolve that amount of drugs in such a small volume.

I agree with Dr Bertelsen, the concentrations (especially additive) are too high to provide a true solution. As it is for gavage, does it matter is it is "paste" so long as it passes down the gastric tube?