SWALE - T Cyp half life considering Bolus size and Concentration

[1cc]

Does the concentration of the Testosterone Cypionate and the bolus size affect it’s half life.

For example, if one was to inject 100mg of 200mg/ml T Cyp, the half life is supposed to be about 5-7 days. If one was to inject 20mg of 200mg/ml T Cyp, would the half life still be 5-7 days, or would it become much shorter?

Would it be better for someone who is injecting 20mg/ml of T Cyp, to use a lower concentration, like 100mg/ml, or even less maybe, like 50mg/ml?

This is a quote from SWALE at the following link:
“Injection site, general activity level, overall health, individual metabolism, size of drug bolus, concentration of same, etc. all influence actual serum levels realized and maintained.”

http://www.sculptedbyiron.com/forum/...6&postcount=42

Bolus = http://dictionary.reference.com/search?q=bolus

[pmgamer18]

I don't think the half life has anything to do with the dose.

[BigRagu]

the half life is the time it will take in the body to degrade........it's not the speed of absorbsion.......

[1cc]

Originally Posted by BigRagu

the half life is the time it will take in the body to degrade........it's not the speed of absorbsion.......

Thats what I thought too, but the quote above by SWALE seems to say different.

[jboldman]

ok, if we look at blood levels i think we can come up with some answers. This would be a good place to refer people to medibolics.com for a further discussion of some of the following. In a study by Schulte-Beerbuhl M et al (1) they found that 140mg of cyp (single injection) returned to basal levels by day 10, that would be a terminal halflife of 5 days. In another study done by Nankin HR(2) with a single injection of 200mg of cyp, test levels returned to baseline after 13 to 15 days, that would be a terminal halflife of 6.5 to 7days. So it would seem that higher mg/ml content would result in a longer terminal halflife in the order of a few days. In a study by Zhang et al (3) they demonstrated that the half life of TU was increased from 18 to 23 days by increasing the single injection size from 2ml to four ml at the same concentration. (500mg tot. to 1000mg tot). The issue of larger bolus sizes is also addressed in the oft quoted minto study (4) "Injection technique, including injection site, volume and concentration, as well as the nature of the vehicle, could theoretically be important for androgen ester release rate." The minto study also brings up the importance of the vehicle (oil) and the impact this has on the release rate of the ester and halflife of the drug. a good example of this is a study done by Behre et al (5) which demonstrated ~50% increase in halflife using castor oil vs tea tree oil.
The Minto study also pointed out that injection site makes a huge difference in bioavailablity and other pharmacokinetics of drugs noting that gluteal injections are much more "efficient" than deltoid. This may likely be due to muscle type.

What does all of this mean? In the minto study, the individual results were fairly diverse reinforcing what we already knew, that different individuals respond differentlly. It would also seem that injection volume, concentration, vehicle, and sites are the other important variables. As you can see, anyone who just plugs their doses into any of the commonly available steroid spreadsheets is still operating in the dark.

jb

1. Schulte-Beerbuhl M et al., Comparison of testosterone, dihydrotestosterone, luteinizing hormone, and follicle-stimulating hormone in serum after injection of testosterone enanthate or testosterone cypionate. Fertility and Sterility (1980) 33.2 : 201-203.

2. Nankin HR, Hormone kinetics after intramuscular testosterone cypionate. Fertility and Sterility (1987) Jun; 47.6 : 1004-1009.

3. J Androl. 1998 Nov-Dec;19(6):761-8.
A pharmacokinetic study of injectable testosterone undecanoate in hypogonadal men.

4. Pharmacokinetics and Pharmacodynamics of Nandrolone Esters in Oil Vehicle: Effects of Ester, Injection Site and Injection Volume1
Charles F. Minto, Christopher Howe, Susan Wishart, Ann J. Conway and David J. Handelsman
http://jpet.aspetjournals.org/cgi/content/full/281/1/93

5. Eur J Endocrinol. 1999 May;140(5):414-9.
Intramuscular injection of testosterone undecanoate for the treatment of male hypogonadism: phase I studies.

[1cc]

JB,

You are the man! Thanks for this great information. Much appreciated.

From your post, among the other factors, it is quite obvious that injection volume (amount of oil) plays an important part in the half-life of injectable Testosterone.
One can also deduce that if one’s T dosage is smaller, like 40-100mg per week, it might actually be better to use a lower concentration injectible Testosterone, like 100mg/ml instead of 200mg/ml. Using the 100mg/ml (more oil), should allow for a longer half life for the smaller weekly dosage, whereas using 200mg/ml (less oil) for the same dose would probably lead to a smaller half-life.

Would you agree with this JB?

Thanks,

1cc

[jboldman]

that's an interesting question, you are suggesting that 1 ml of 100mg/ml would have a longer half-life than .5ml of 200mg/ml. While i suspect that this would be true the absolute difference of the half life might be too small to really make much difference. It might be better to make it up with castor oil if your interest is to extend the stay of the test in your body. and even more effective you could play around with test undecanoate to see a really long half life that shows imo a great deal of promise for trt.

jb