Transdermal (i.e., medication is absorbed through the skin)
In general, most transdermal forms of prescription testosterone (such as gels, creams, and patches) contain bioidentical testosterone. Because bioidentical testosterone becomes active quickly once absorbed through the skin, it must be applied daily to maintain appropriate levels of testosterone in the body. Depending on the formulation, transdermal preparations might also include additional ingredients to accelerate the absorption of the testosterone through the skin. Some of these ingredients can cause side effects, such as rashes and skin irritation. Transdermal testosterone is available in both brand-name and compounded preparations; a prescription for compounded transdermal testosterone can be tailored by your doctor for your specific dosage requirements. (For more information on transdermal testosterone systems, see the Testosterone Types and Delivery page. For more information on compounding, see the Compounding Pharmacies page.)
Sublingual/buccal
Sublingual and buccal testosterone treatments, which are dissolved in the mouth rather than swallowed, are generally made with bioidentical testosterone. Sublingual preparations are dissolved under the tongue; these can be prepared by compounding pharmacies. Buccal testosterone delivery works placing a tablet against the surface of the gums. Buccal testosterone systems are available as name-brand or compounded preparations. Sublingual/buccal delivery is different from oral delivery in that very little of the substance is swallowed, avoiding potential "first pass effect" problems with the liver. Because bioidentical testosterone is absorbed quickly through sublingual/buccal routes, it must be applied more than once a day to maintain appropriate levels of testosterone in the body. (For more information on sublingual and buccal testosterone systems, see the Testosterone Types and Delivery page. For more information on compounding, see the Compounding Pharmacies page.)
Subcutaneous pellet
Subcutaneous testosterone pellets are made of bioidentical, crystalline testosterone that is implanted beneath the skin. The pellets are about the size of a grain of rice, and are typically placed in the buttocks or abdomen by a doctor. Because of their crystalline form, the testosterone in subcutaneous pellets is released slowly over a period of weeks or months. (For more information on subcutaneous testosterone systems, see the Testosterone Types and Delivery page. For more information on compounding, see the Compounding Pharmacies page.)
Injectables
As mentioned previously on this page, injectable testosterone is prepared mainly in the form of testosterone esters such as testosterone cypionate or testosterone enanthate. (For a more detailed description of testosterone esters, see the Testosterone Types and Delivery page.) Because a testosterone ester is a modified form of the testosterone molecule, it should not technically be considered a bioidentical form of testosterone. However, when testosterone esters are released into the bloodstream, the ester group is cleaved off by "esterase enzymes" in a process known as "hydrolization." Once the ester group has been removed by these enzymes, the testosterone is returned to its free, bioidentical form, thus making it bioavailable and ready to perform its various actions and effects. (For more information on injectable testosterone systems, see the Testosterone Types and Delivery page. For more information on compounding, see the Compounding Pharmacies page.)
Oral
Bioidentical testosterone is never taken orally since it will be immediately deactivated by the liver due to the "first pass effect." Two non-bioidentical forms of testosterone have been used in testosterone therapy: methyltestosterone and testosterone undecanoate.
As mentioned previously, methyltestosterone is one of the earliest available oral testosterones. Its chemical structure is the hormone testosterone with an added methyl group at the c-17 alpha position of the molecule. The use of oral c-17 alpha methylated testosterone is not recommended due to its potential toxicity to the liver.
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