Bioequivalence and Bioavailability Forum

Hi drgopal!

Let’s consider 2 phases were degradation may occur: clinics and analytics.

Clinics
Generally lightsensitive drugs are well protected during sampling, because:

1. Glas vials (vacutainers) are almost perfect shields for UV-radiation.
   
2. The entry-depth of light into whole blood is in the range of a few millimeters only.
   
3. If your compound has a similar absorption wavelength as compared to albumin, such a compound may be well protected after centrifugation in plasma / plastic tubes.

In my experience working in the clinical stage under light protection (e.g., sodium vapour lamps) leads to a lot of difficulties in venipuncture, sampling errors, etc.
Plasma vials (3) may be wrapped in aluminium foil or dip-coated.

If you are over-cautious, you may try to validate 1 & 2, but:
be prepared to difficulities anyway, because you would have to spike whole blood in vacutainers. IMHO, you end up with very variable results; therefore more than the usual 6 replicates must be considered.

Analytics

1. Analytes in stock solutions and sample extracts are much more susceptible to light-degradation than plasma samples.
   
2. You should validate all sample preparation steps under varying light conditions (day light through [closed!] windows, fluorescent light, dimmed light, sodium vapour light), and different light protection measures (glass vials, brown glass vials, PP vials, etc).
   
3. Dont’t forget to close the lid of the autosampler.

As in clinics, the dimmer the light the more sample preparation errors are likely to occur.
You should find an optimum between sufficient light protection and practicability.