PT: an interesting fact about Dexamethasone

[Godmother]

I was looking at a web site about how PT shows up in humans, and I found an NIMH site describing the Dexamethasone suppression test.
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0004158/

It states that the response to a high dose (vs a low dose) of Dex distinguishes a Pituitary tumours from other causes. Is that why Dex can give a faster response than Pred for our rats with PT?

 

[lilspaz68]

from http://ratguide.com/meds/endocrine_horm ... hasone.php

Dexamethasone is a long acting florinated glucocorticoid with 25-30 times more potency than an equal weight of hydrocortisone. It is faster acting with longer duration than the intermediate oral agents prednisone and prednisolone. In dogs, the drug has been shown to have a half-life of 2 to 5 hours with biologic activity of up to 48 hours.
Dexamethasone stimulates synthesis of enzymes required to decrease the inflammatory response. Its primary efficacy is that of a strong anti-inflammatory, as well as an antiallergic agent.

What is a biologic activity?

I think its faster so you see a quicker and more dramatic result to the reduction of the swelling causing the PT symptoms.

 

[SQ]

So does that mean that dex is not more efective in the long term then pred?
I thought it was much better then pred for neurological issues ....

 

[Joanne]

So does that mean that dex is not more efective in the long term then pred?
I thought it was much better then pred for neurological issues ....

Dexamethasone is a long acting florinated glucocorticoid with 25-30 times more potency than an equal weight of hydrocortisone. It is faster acting with longer duration than the intermediate oral agents prednisone and prednisolone.

 

[lilspaz68]

Also

Dexamethasone is preferred over prednisone for use in rats.

 

[jorats]

the drug has been shown to have a half-life of 2 to 5 hours with biologic activity of up to 48 hours.

This means the drug has an effect of up to 48 hours but it's half life is 5 hours. So that means it takes 5 hours for half your dose to disappear.

 

[Rattus]

hmm.. so wouldnt that mean you would have to give it way more often then pred? that could be difficult..

 

[Joanne]

hmm.. so wouldnt that mean you would have to give it way more often then pred? that could be difficult..

Half life is just how long it takes to reduce the drug level by 50% in your body.
This is not the same as biologic activity which Jorats said was up to 48 hours.