| interaction of preservatives with the other ingradients of the prep | |||
| cps that are commonly used in formulation as emulgents ,adjuvants ,thickners ,and filling agents | inactivate many preservatives | ||
| kaolin ,talc ,chalk ,zinc oxide ,colouring matter | natural source of electric charge (adsorb pres) | ||
| several non ionics inactivate variety of pres either by H.B or solubilization in the micelle ,, characteristics of non ionics as HLB and solubilization | inactivate Q.A.S ,hydroxybenzoate ,phenols ,chlorobutol and organic mercuric cpds | ||
| favorable effects of non ionics | |||
| 1-type of non ionic eg | |||
| mono-esters of poly-glycols | inactive | ||
| poly-glycol ethers | effective | ||
| 2-germicide non ionic ratio | |||
| tweens when present at high level | antagonizing effect | ||
| low ratios 1 part germicide to 20 parts non-ionic | effective for potentiation of antibacterial activity of trichloro-carbanilide | ||
| 3-preservative type | |||
| benzalkonium chloride ,chlorohexidine and polymyxin B # Ps. In prersence of 0.02% polysorbate 80 | enhanced effect ,but polymyxin B was eleminated when high level of non ionics | ||
| other examples | |||
| Gum trgacanth in 3% soln | inactivates chlorobutanol ,organic mercury cpds and benzalkonium | ||
| methyl cellulose | interact with esters of p-hydroxybenzoic acid | ||
| polyvinyl pyrrolidone (p.v.p) which contain amide gp | inactivate cpds like phenols (proton donars) form complex with amides | ||