@Johnny 4972 wrote:

What is your opinion of the new testosterone treatment called Nebido?

Many people are very skeptical towards this treatment, but I have read about many users who actually prefers it over frequent injections and feel great on it.

Nebido is testosterone undecanoate dissolved in caster oil and Benzyl benzoate.

Testosterone undecanoate is a testosterone ester just like testosterone cypionate or testosterone enanthate.

The biggest difference is that the half-life of testosterone undecanoate is enormously long. Testosterone cypionate has an average half-life of about 7 days. Testosterone undecanoate has a half-life of 90 days (±40 days).

Testosterone cypionate, usually, needs to be injected every 7 days to maintain a reasonably steady level in the bloodstream. The average dose is 100 mg each week (a 1/2 mL injection). Some practitioners actually do well by injecting patients with a 400 mg dose each month. Some patients need to inject every 3 days since the half life for them is much shorter than 7 days.

Testosterone undecanoate has to be injected about every 90 days (give or take a few weeks). The average dose is 1000 mg every 3 months (a 4 mL injection)

Once the ester chain is cleaved by enzymes in the body, testosterone is freed to act. Thus, there should be no difference in effect so long as the dosing is optimized for the person.

The advantage of a very long half-life is that the steady state blood level is going to be very flat – with less acute ups and downs compared to the shorter acting testosterone esters. For some men, this eliminates the ups and downs in mood and function they experience (the roller coaster effect). Testosterone undecanoate’s effect is very similar then to transdermal alcohol gels (such as Androgel), where the steady state level of testosterone is very flat.

The long-half life may also reduce the risk of having high estrogen levels from treatment. This is seen, for example, in pellet testosterone implants – which are also changed every 3 months.

The disadvantage of a very long half-life is that it takes a very long time to stabilize the dose – about a year. So dose optimization is going to take a long time. It is like trying to turn a large ship around compared to a small speedboat.

Testosterone undecanoate is very convenient to use in that the injection only needs to be given 4 times a year. It is a large 4 mL injection which has to be injected very slowly into the buttocks.

I like the convenience and that flatness of the testosterone stead state blood level and the lower risk for excessive estrogen production. The effect should be similar to successful transdermal alcohol-based testosterone gels or implanted testosterone pellets.

Bayer Pharma AG produces Nebido. Endo Pharmaceuticals has the rights to it in the U.S. They renamed it Aveed. Unfortunately, the FDA rejected the application for Aveed in December 2009.

The FDA cited two reasons:

1. Some patients got anaphylactic reactions to Nebido/Aveed. This means unless injected by a doctor who is in a clinic ready for an anaphylactic reaction, the patient could instantly die. And even if the patient did not die, the patient is in for months of trouble since the injection lasts longer than 3 months.

2. Some patients developed pulmonary microembolisms from the oil component of Nebido/Aveed (a sign of this is difficulty breathing or a cough after injection).

Unlike testosterone cypionate and enanthate which dissolve the testosterone ester in sesame seed or cottonseed oil, Nebido unfortunately dissolves the testosterone undecanoate in caster oil. Unfortunately, injecting caster oil into a patient leads to the risk for microembolisms.

Testosterone undecanoate is very promising a treatment.

Unfortunately I don’t like the use of caster oil which risks microembolisms (which potentially can lead to lung tissue destruction and embolic problems. (It is the oil that kids where forced to drink as punishment years ago.). I hope it can be reformulated using a different oil.

To avoid the potentially fatal anaphylactic reaction, there should be a tiny dose that can be used in a skin test before giving the huge 4 mL injection that lasts more than 3 months in the body.

Did not know about the issue with emboli. That seems serious!