Forced Degradation HPLC (stability indicating Method)

[LC_addict]

Hi Guys,

Another student Q.

I need to prepare a 'stability indicating method. Best way to determine Degradation would be forced Degs...right?

Now how do i know i am 'forcing' this enough? How do i know my peaks will elute using the same method? How do i determine whether they are/ arent coming off in the solvent front? Must be a way to determine this or i could miss peaks?!

LC

[aceto_81]

A search on the forum will get you started, as the topic comes up from time to time.
To go short: usually the API is degradated to 80 - 90% recovery, so 10-20% degradation.
This to avoid formation of secondary degradation products.

To address missing peaks, you can check your mass balance, eg sum your % impurities and % api, this should be around 100%,in case of a very low mass balance, it's possible that you are missing peaks, or the response of the degradations product is different.


HTH

Ace

[Consumer Products Guy]

Personally, I find "forced degradation" to be the "grayest of the gray" parts of a chromatography validation.

The way I understand it, the goal is to ensure that any degradation products would not (1) elute at same retention time as the API and (2) have similar detector response as the API if (1) occurs.

We have no issues if the API is an ester (such as a sunscreen product) where under saponification the degradation products have different retention times or elute just after the dead volume. But some of our API actives just won't degrade whatever we do, so to keep trying that would require years, not practical.

Our products are mostly topical products that are pH-controlled, and pH is measured at all stability timepoints, so is heating for days in concentrated acid a practical test anyway? What about exposure to light when product is in a light-barrier container.

Typically we go through the motions with heating product with acid, heating with base, light exposure (UV and visible), peroxide exposure. We use diode-array detector to show that the spectrum of the API peak is same as its control. So not much value, imagine this is a carryover from just using UV-visible spectrophotometer when one couldn't know if degradation products might still have UV comparable to a non-degraded API.

[zheyin]

Personally, I find "forced degradation" to be the "grayest of the gray" parts of a chromatography validation.

The way I understand it, the goal is to ensure that any degradation products would not (1) elute at same retention time as the API and (2) have similar detector response as the API if (1) occurs.

We have no issues if the API is an ester (such as a sunscreen product) where under saponification the degradation products have different retention times or elute just after the dead volume. But some of our API actives just won't degrade whatever we do, so to keep trying that would require years, not practical.

Our products are mostly topical products that are pH-controlled, and pH is measured at all stability timepoints, so is heating for days in concentrated acid a practical test anyway? What about exposure to light when product is in a light-barrier container.

Typically we go through the motions with heating product with acid, heating with base, light exposure (UV and visible), peroxide exposure. We use diode-array detector to show that the spectrum of the API peak is same as its control. So not much value, imagine this is a carryover from just using UV-visible spectrophotometer when one couldn't know if degradation products might still have UV comparable to a non-degraded API.

How do you use the purity value and threshold in the spectrum from the software,
I am confused about how to interprete the numbers from ChemStation and how to set up the evaluation.

[prepcolumn]

Zheyin

Forced degradation is a subject which is really tough to summarize and generalize. Because you need a priliminary information about the active substance and the tendency of chemical reactivity through different conditions (which is not always possible or may change your sample is drug substance or drug product).

But primary point is decomposing the sample around 10% to avoid unrealistic impurities and to achieve mass balance.

Pharmacutical Stress Testing Predicting Drug Degradation, Steven W. Baertschi, Taylor-Francis Group is a really good book on this subject (i think you may find as e-book)

Alsante Karen M. et al, Advenced Drug Delivery Reviews, 59 (2007) 29-37 is a paper which is also helpful (let me know if you cannot reach the paper)

[prepcolumn]

Sorry..previous post was to LC_addict

[zheyin]

I was asked to figure out how to do this part of validation.
From the previous posts, I understand:
1) Forced degradation methods (duration and condition) are to be determined for your APIs.
Target is to generate 10-20% impurities to avoid secondary degradation
(assuming UV response factors are similar to calculate 100% mass balance)
This part requires some "LUCK" depending on what compounds you have.

2) With UV spectrum, to evaluate if there is any co-elution at the same retention time of the API.
My current lab does not have MS, so DAD is the only option.
How to compare the degraded with the control?
Just compare the two spectra at the API peak?
OR use the purity and threshold values from the software and HOW? (I am using ChemStation)

This is the part I am trying to seek help with.

3) If significant amount of degradant co-eluted as the API (observed from the spectra), this method would not be validated.
And a modification of the method is required to separate the degradant from the API.