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Re: FH value and DHS cycle considerations.

Manoj

I have answered you questions using UPPERCASE below

THESE ARE VIEWS BASED ON MEMORY SO PLEASE DONT 
TAKE IT LITERALLY BUT HOPEFULLY IT SHOULD PROVIDE 
INFO TO GET THE THOUGHTS FLOWING. THERE ARE SOME 
USEFUL REFERENCES AROUND ESPECIALLY ON THE PDA 
WEBSITE.


1.Is FH calculation having any significance 
against Challenging Dry heat sterilization cycle 
with Biological indication and Endotoxin 
challenge?
FH PROVIDES A MEANS OF CALCULATING THE TIME 
EQUIVALENT AT YOUR STERILISING TEMPERATURE. IN 
YOUR CASE 160C. THIS IN TURN CAN BE USED TO 
DETERMINE YOUR STERILITY ASSURANCE LEVEL BASED ON 
THE MODEL YOU CHOSE FOR VALIDATION. IF YOU USE 
THE BIOLOGICAL INDICATOR MODEL YOU WILL HAVE A BI 
AT A LOADING OF 10^6 (?) THEREFORE IF YOU KNOW 
THE  D VALUE YOU CAN CALCULATE THE SAL YOU HAVE 
ACHEIVED.

FOR ENDOTOXIN THE APPROACH IS SIMILAR BUT YOU 
CALCULATE FP. YOU WILL NOT DEPYROGENATE UNDER DRY 
HEAT STERILISING CONDITIONS. YOU WILL STERILISE 
UNDER DEPYROGENATION CONDITIONS

2.As for FH calculation Z values is available 
49C calculated at 160C by the Biological 
indicator supplier.

Is this Z value will helpful for calculating FH, 
at 200C operating temperature?
YES BECAUSE IT IS A MEASURE OF WHAT TEMPERATURE 
CHANGE WILL CAUSE LOG D VALUE TO CHANGE BY 1 LOG.

IF I RECALL CORRECTLY (PLEASE CHECK LITERATURE AS 
THIS IS FROM MY POOR OLD BRAIN)

FH = 10^{(T-160)/Z} = 10^0.82 = 6.5 minutes

wHICH IF YOU SUBSTITUTE T FOR 200 MEANS THAT 1 
MINUTE AT 200c IS EQUIVALENT TO APPROX 6 MINUTES 
AT YOUR SPECIFIED TEMP OF 160C

3.For sterilization/Depyrogenation cycles, most 
of the industries set the temperature above then 
the required one i.e. if required temperature is 
200C, the temperature setting kept at 210C so 
that it will not be below than the standard set 
temperature. (Safety margin).

In above described case whether the temperature 
for cycle time consideration should be taken from 
200C or 210C.Because the hold period will start 
from achieving 210C on-ward.
DEPENDS ON YOUR LOAD YOUR STERILISATION MODEL 
ETC. IF YOUR LOAD CAN TOLERATE IT THERE SHOULD 
BE NO ISSUES. AT THE TEMPS YOU QUOTE I WOULD 
ONLY VALIDATE THE DEPYROGENATION ELEMENT. THIS 
WILL ALSO COVER STERILISATION

4.Is it required to do the Empty chamber 
temperature studies using Biological indicators?
I HAVE SEEN IT DONE ON THE BASIS (WITH RAPID 
METHODS OF BI ASSESMENT) THAT IF I COULD NOT 
STERILISE IN AN EMPTY CHAMBER DO I WANT TO RISK A 
PRODUCTION LOAD?

FOR DRY HEAT AT 200c I WOULD NOT BOTHER. I WOULD 
JUST USE ENDOTOXIN CHALLENGES LOAD

I WOULD MAP THE CHMABER (HEAT DISTRIBUTION) 
BEFORE I DO A LOAD (HEAT PENETRATION)

5.After two-three re-validations, Reduced number 
of Biological indicators/Endotoxin challenge is 
acceptable?
IMPOSSIBLE FROM ME TO COMMENT WITHOUT KNOWING THE DETAIL.

ONE THING TO WATCH FOR ON DRY HEAT LOADS IS YOUR 
DEFINITION OF WORSE CASE LOAD. IT MIGHT ACTUALLY 
BE THE SMALLEST LOAD (LEAST MASS) NOT THE BIGGEST 
LOAD (HIGHEST MASS)  DEPENDS ON THE HEATING 
METHOD AND SIZE OF CHAMBER.



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