Unstable Phase Mixtures – Topical Medications

00:01 Now, we have a unique category of delivery vehicles called unstable phase mixtures.

00:07 So these are what we call biphasic liquids. So you can see an example here of a biphasic liquid.

00:12 If you look carefully on this bottle, there's actually two phases on the bottle.

00:17 On the bottom, there's a water phase and on the top, there's an oil phase.

00:22 Now you have to mix them into this kind of milky substance for it to be activated.

00:28 Now, why in the world would you have something like this? Well, if you have a drug for example that will interact with the emulsifier, you wanna keep them separate until the last possible moment.

00:43 Now, it's mostly used in so-called natural product where the marketing strategy is to minimize ingredients with long names.

00:51 So I already told you that emulsifiers maintain a stable mixture of two products that are normally non-mixable or immiscible.

00:59 So if you wanna avoid using the emulsifier which has a long name and scares people without education, then you can use a biphasic liquid.

01:09 Emulsifiers that we commonly use so that we don't have to use a biphasic liquid include these different products.

01:17 All of these products are safe.

01:20 We also have unstable phase mixtures with biphasic suspensions.

01:28 So a suspension is a component that has a solid component, usually a powder.

01:34 And then the continuous phase which is some kind of a liquid.

01:38 The important aspect of this though is that the powdered substance is so heavy that there is absolutely no way that they would maintain their stability.

01:49 Here is an example of a cosmetic product that actually uses it's -- they call it mud.

01:55 But really, it's crushed up rock that is suspended in an oil phase.

01:59 These are -- this one here is a cosmetic with a clay particle.

02:03 I can't really discern why people would use this product but it's actually fairly commonly used.

02:10 We also have tints, T-I-N-T-S, tints. These are often using metals and stone to give it color.

02:18 So an example of this are color rising topical paints.

02:24 Now, we don't think of this as a medication but remember, patients are going to be applying these colorizing paints to their skin during costumes and parades and things like that.

02:36 And these can have toxic consequences.

02:38 So we as physicians need to know how they're made, why they're made, what they're doing with them and what the different components are.

02:45 There's other things that we also look at called supersaturated solutions.

02:50 And a really good example of that is supersaturated solution of potassium iodide.

02:55 Potassium iodide is a compound with a relatively high molar mass.

02:59 We sometimes use supersaturated solutions of potassium iodide for the treatment of certain disease conditions like erytheme nodosum.

03:07 These are very hard to make. They often end up precipitating out.

03:12 But if you have a particularly skilled pharmacist, they'll be able to maintain the saturated or supersaturated phase in a continuous stable medium.

03:22 Okay, that's it. I told you it would be quick, but it will be useful when you get out into practice.