Mechanism: cytokine release
Protocol:
(1) Select 8 healthy adult rabbits free of infection and raised under controlled conditions.
(2) The baseline temperature for the rabbits is recorded and the rabbits weighed. The temperatures for all 8 rabbits should agree within 1 degree of each other and not be above normal.
(3) All needles and syringes are pyrogen free.
(4) Solutions are kept at 37°C.
(5) The drug solution is injected into the ear vein of 3 initial rabbits at a dose of 10 mL per kg body weight.
(6) Temperatures of injected rabbits are recorded every 30 minutes for 3 hours.
(7) If any of the rabbits in the initial group show a temperature rise >= 0.5°C after the injection then the remaining 5 rabbits are injected.
change in temperature in °C for a rabbit =
= (maximum temperature in °C) - (baseline temperature in °C)
number of rabbits showing temperature rise above threshhold =
= SUM(number of rabbits with change in temperature >= 0.5°C)
cumulative temperature rise in °C =
= SUM(change in temperature for all rabbits tested)
Criteria for a negative pyrogen test - one of the following:
(1) none of the first 3 rabbits have a temperature rise >= 0.5°C
(2) no more than 3 rabbits out of 8 have a temperature rise >= 0.5°C AND the cumulative temperature increase in all 8 rabbits is <= 3.3°C
Limitations:
• The presence of an occult infection can cause a false positive test.
• A drug may cause a temperature rise by impacting metabolism, cytokine release or CNS temperature control centers, resulting in a false positive.
• A false negative test may occur if the concentration of pyrogens is very low.
