The partition coefficient of the ester in question is important because is effects how long the drug itself stays in the system. If the testosterone transfers too quickly from the oil to the blood, the result is a sudden spike in testosterone which then rapidly drops once the dose has been used up. In the example of free testosterone injected into the muscle from a water suspension (as in Aquiviron, mentioned above), the testosterone is essentially immediately available to the bloodstream due to its low partition coefficient, and thus there is an immediate spike of testosterone which is used up quickly in the body.
• Evaluate formulation-specific adverse effects at each visit:
- Intramuscular injections of testosterone enanthate and cypionate: Ask about fluctuations in mood or libido.
- Testosterone patches: Look for skin reaction at the application site.
- Testosterone gels: Advise patients to cover the application sites with a shirt and to wash the skin with soap and water before having skin-to-skin contact because testosterone gel leaves a residue on the skin that can be transferred to a woman or child who comes in close contact. Serum testosterone levels are maintained when the site is washed 6 hours after applying the gel.