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Testosterone Propionate has fallen out of favor for treating hypogonadism due to short half life of 3-4 days, requiring frequent injections, high risk of aromatization, and the side effects of high estrogen levels; unlike Testosterone Cypionate or Enanthate which are similar, long-acting* with longer half life of 7-8 days, safer with minimal, manageable side effects, and have become the mainstay of treating low-T with testosterone injections, both intramuscular as well as subcutaneous.
*Both cypionate and enanthate can be injected weekly or biweekly, monthly or if following micro-dosing with HCG on alternate days for a steady testosterone boost similar to natural testosterone production in the body.
The safety, manageable side effects, flexibility of frequency and dosage, choice of IM or subQ of both cypionate and enanthate has made propionate redundant.
Testosterone propionate is now sold only in compounding pharmacies in the US, whereas cypionate and enanthate are easily accessible both generic and branded forms, with choice of injecting intramuscular or subcutaneous. Propionate is solely intramuscular.
Propionate is available for veterinary purposes, but commercially propionate for androgen replacement in humans is stopped due to more efficient and safer esters like cypionate and enanthate.
Propionate was the very first testosterone ester formulated and prescribed for androgen replacement in the 1950s, before better esters like cypionate and enanthate came along.
While its properties of quickly peaking in the blood plasma within hours and rapid metabolizing can rapidly increase testosterone levels, the side effects from increased estrogen – gynecomastia, increase fat mass, oedema counters the benefits. since frequent injections are necessary with a short half life of 3 to 4 days.
*Testosterone propionate presents a slow absorption from the intramuscular site of administration. This slow absorption is due to the presence of the less polar ester group.
The absorption rate of testosterone propionate generates a frequent injection requirement when compared with testosterone enanthate or testosterone cypionate.
It presents absorption parameters of AUC and residence time of 180-210 ng h/ml and 40-60 h, respectively”
*Excerpt from https://go.drugbank.com/drugs/DB01420
Like other esters testosterone propionate cleaves into free testosterone in blood plasma. Propionate rapidly metabolizes to 17-keti steroids through two different pathways. Estradiol which leads to estrogen synthesis and binding directly to an androgen receptor leads to dihydrotestosterone(DHT) synthesis.
Propionate has to be prescribed carefully weighing pros and cons, and in specific cases like late onset of puberty, breast cancer in women.
Propionate is prescribed in Canada, in Europe and a few other countries where it is used in combination with a longer acting testosterone esters to avoid peaks and valleys.
Testoviron Depot 50 and 100, is a combination of testosterone propionate and enanthate, Sustanon 100 and 250, combines testosterone propionate, phenylpropionate, isocaproate, and decanoate.
But these combination esters result in higher testosterone peaks with no added benefit of longer duration of action, so it is not an ideal treatment to start with, like testosterone cypionate or enanthate for treating low -T symptoms.
Other proprietary blends of long-acting short-acting testosterone esters, combining propionate with cypionate and other esters exist.