Chemical Designation: 4-Hydroxyandrost-4-ene-3,17-dione
Formula: C 19 H 26 O 3
Molecular Mass: 302.408 g/mol
Active Ingredient: Formestane
Inactive Ingredient: Sodium Chloride
Half-Life: Approx. 30 Hours
Lentaron, a.k.a. formestane, belongs to a class of drugs known as 2 (or second generation) aromatase inhibitors which are primarily used in the treatment of estrogen-receptor positive breast and ovarian cancers in post-menopausal women. Some cancers require estrogen to grow, and aromatase is an enzyme that synthesizes estrogen. Aromatase Inhibitors (AIs) are a class of drugs that effectively block this synthesis thereby lowering estrogenic levels, and slowing the growth of cancers.
AIs are categorized into two types: 1) non-steroidal inhibitors such as Arimidex (anastrozole) and Femara (letrozole) which inhibit the enzyme by reversible competition and; 2) irreversible steroidal inhibitors such as Aromasin (exemestrane) which form a permanent bond with the aromatase enzyme complex. Lentaron is classified in the second group as a selective irreversible steroidal aromatase inhibitor. Derived from androstenedione (the same except for the addition of a 4-hydroxyl group), formestane forms an irreversible bond with the aromatase enzyme which permanently deactivates it. It takes several days (following formestane discontinuation) for aromatase to become active again. These types of drugs are often referred to as suicidal aromatase inhibitors because the drugs seemingly sacrifice themselves (their structural independence) in the process of blocking estrogen.
Lentaron is available as an intramuscular depot injection, and is often found in 2 ml ampules of 125 mg/ml solution. The recommended dosage for bodybuilder purposes is the same as that for advanced breast cancer therapy, namely 250 mg per week. Formestane can also be found, and taken in the same 250 mg per week dosage in its oral form, but the oral had poor bioavailability is no longer a popular version of this drug.
Aromatase converts androstenedione to estrone, and also converts testosterone to estradiol. Lentaron is often used to suppressestrogen production during anabolic steroids and prohormone cycles. Due largely to Lentarons similarity to androstenedione, it also acts as a prohormone to 4-hydroxytestosterone , an active steroid which displays weak androgenic activity in addition to serving as a mild aromatase inhibitor.
Male bodybuilders and athletes also use it to prevent estrogenic side effects from anabolic steroids, to improve fat loss, and to increase muscle definition while dieting. However, several conclusive studies have demonstrated Lentarons estrogen blocking inferiority when compared to third generation AIs like Arimidex (anastrozole) and Femara (Letrozole) so its far less popular.
The side effects which accompany Lentaron use are also those that are common to other AI drugs including fatigue, mood swings, depression, joint pain, hot flashes, headaches, swelling of the arms and legs, and high blood pressure. AIs also suppress HDL (good) cholesterol levels, and may decrease bone density increasing susceptibility to osteoporosis, fractures and breaks.
Lentaron is not widely available as a prescription drug, and is therefore infrequently found within steroid circles. It is very effective when added to anabolic cycles of aromatizing steroids like Dianabol, testosterone (cypionate, propionate, and enanthate), Trenbolone, and Deca-Durabolin.