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Question

Posted on: March 6 2013

An ophthalmologist wants to prescribe a variant on the specialty bacicoline masterly polymyxin B 100,000 e bacitracin 50,000 e hydrocortisone (or acetate) 1 g (sic!) After

Borate 0.5% (intends borate buffer)
Physiological Water AD 10 (TEN) ml < BR/> This can remain stable for a month at a certain pH value (Which?); -The droplets should be ISO to light Hypertone (previous preparations were found to be pricked in the eye, according to the physician); -To what extent would the use of a soluble salt of hydrocortisone the operation be ï Nvloeden.
of Bacitracin is said to be not stable in aqueous solutions, even with propylene glycol. For polymyxin You can install a neutral pH with the borate buffer. The hydrocortisone will Wsch. Can be replaced by a soluble salt of a more potent cortico, whose concentration can therefore be reduced. However, Martindale indicates that polymyxin B is not compatible with BVB. Prednisolone Sodium phosphate!
The example in the Question box with dexamethasone, Neo and polymyxin is analogous but has a limited antibacterial spectrum (VNL. Against Gram-).
Frankly, I don't see it sitting down to make that with the standard pharmacy equipment Deftig, even if we would find a good formulation...

Answer

I can give you the following example of droplets that will appear in the second part of the TMF. While you are concerned about the stability of bacitracin, where we deliver many bottles of Neo bacitracin every day. So I would say apply same storage conditions and shelf life;
polymixin B sulfate 100,000 IU
dexamethasone naphosphate 7.2 mg But it may be equally good after prednisolonphosphate
Neomycin sulfate 50 mg
Propylene glycol 1 g
excipient up to 10 ml
excipient
Citric acid 1 aq 112.5 mg
after citrate 7.5 g
after EDTA 250 mg
water to 250 ml
the incompatibility mentioned in the Martindale, the opalescence that arises, could be avoided by pre-advance of certain Protective anions such as citrate. If the pH of the solution comes out of 5-7 plymyxin B sulfate precipitates. A solution citric acid citrate appears to be a good solvent for this combination of drugs. Benzalkonium chloride is incompatible with polymyxin B sulfate. The droplets are preserved with propylene glycol. 10% should be feasible in a not too sensitive eye?

Preparation method
(1) Take 4 ml of the excipient and dissolve in successively: neomycin sulfate and Polymyxin B sulfate.
(2) Take a second quantity of 4 ml excipient and dissolve in it: dexamethasone (prednisolone) sodium phosphate.
Add, under Mix, (1) gradually (2) and fill with excipient up to 10 ml.

for eye drops, this solution is filtered sterile. For certain ear drops, this filtration can also be desirable!

Perhaps this requirement can serve as a starting point? I suspect that this is still feasible for the Officina? After all, this formula is published as an eardrop in TMF 2, albeit with 20% propylene glycol! I have compiled them and Prof. Hoogmartens has studied stability for 2 months. Was OK.