This medication is used in men who do not make enough of a natural substance called testosterone. Testosterone belongs to a class of drugs known as androgens. Testosterone helps the body to develop and maintain male sexual characteristics (masculinity), such as a deep voice and body hair. It also helps to maintain muscle and prevent bone loss, and is necessary for natural sexual ability/desire.Testosterone may also be used in certain adolescent boys to cause puberty in those with delayed puberty.This product should not be used in women.

Testosterone undecanoate is a long-acting man-made version of testosterone, the natural male sexual hormone. Testosterone is responsible for the normal growth and development of male sex organs and characteristics. It includes growth and development of male organs of penis, testicles, prostate, body hair, vocal cord thickening, and muscle and fat distribution. The FDA approved testosterone undecanoate in March 2014.
How to use Testosterone Undecanoate Solution
Read the Medication Guide provided by your pharmacist before you start using this medication and each time you receive an injection. If you have any questions, ask your doctor or pharmacist.
This medication is given by injection into the buttock muscle as directed by your doctor. After the first dose, it is usually given 4 weeks later, then every 10 weeks. The dosage is based on your medical condition, testosterone blood levels, and response to treatment.
Use this medication regularly to get the most benefit from it. To help you remember, use a calendar to mark the days you will receive an injection.
Misuse or abuse of testosterone can cause serious side effects such as heart disease (including heart attack), stroke, liver disease, mental/mood problems, abnormal drug-seeking behavior, or improper bone growth (in adolescents). Do not increase your dose or use this drug more often or for longer than prescribed. When testosterone is misused or abused, you may have withdrawal symptoms (such as depression, irritability, tiredness) when you suddenly stop using the drug. These symptoms may last from weeks to months.
Side Effects
Nausea, vomiting, headache, skin color changes, increased/decreased sexual interest, oily skin, hair loss, and acne may occur. Pain or redness at the injection site may also occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.
Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Tell your doctor right away if you have any serious side effects, including: breast swelling/tenderness, mental/mood changes (such as depression, agitation, hostility), unusual snoring or difficulty breathing during sleep, swelling hands/ankles/feet, symptoms of liver problems (such as loss of appetite, persistent nausea/vomiting, severe stomach/abdominal pain, yellowing eyes/skin, dark urine), trouble urinating, increased urination (especially at night), too frequent/prolonged erections, fast/irregular heartbeat.
Get medical help right away if you have any very serious side effects, including: shortness of breath/rapid breathing, chest/jaw/left arm pain, unusual sweating, confusion, sudden dizziness/fainting, pain/swelling/warmth in the groin/calf, sudden/severe headaches, trouble speaking, weakness on one side of the body, sudden vision changes.
Rarely, males may have a painful or prolonged erection lasting 4 or more hours. If this occurs, get medical help right away, or permanent problems could occur.
A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
Before using testosterone, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients (such as benzyl benzoate, refined castor oil), which can cause allergic reactions or other problems. Talk to your pharmacist for more details.
Before using this medication, tell your doctor or pharmacist your medical history, especially of: cancer (especially prostate or breast cancer), prostate problems (such as enlarged prostate), heart problems (such as heart failure, previous heart attack), stroke, kidney problems, liver problems, high cholesterol, difficulty breathing during sleep (sleep apnea), blood clots (such as in the leg, lungs).
Precautions
If you have diabetes, this product may lower your blood sugar. Check your blood sugar regularly as directed and share the results with your doctor. Tell your doctor right away if you have symptoms of low blood sugar, such as sudden sweating, shaking, fast heartbeat, hunger, blurred vision, dizziness, or tingling hands/feet. Your doctor may need to adjust your diabetes medication, exercise program, or diet.
Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Children may be more sensitive to the side effects of this drug. In children, it may affect bone growth. Check your child’s height periodically.
Some men, particularly older adults, are at a higher risk for developing enlarged prostate or prostate cancer while using this medication. Your risk of prostate problems should be checked by your doctor before you start testosterone.
This medication can affect fertility in males. Ask your doctor for more details.
This medication should not be used in women, especially during pregnancy or breast-feeding. It may harm an unborn or breast-feeding baby. Consult your doctor for more details.
Interactions
Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor’s approval.
Some products that may interact with this drug include: “blood thinners” (such as warfarin).
This medication may interfere with certain laboratory tests (including thyroid tests), possibly causing false test results. Make sure laboratory personnel and all your doctors know you use this drug.
Safety and tolerability
So far TU has shown a good safety profile; no major adverse events were seen in any studies, including long-term data collected over 8 years of treatment. TU should be injected deep into the gluteal muscle and though few patients report injection-site pain, concerns of local irritation at the injection site could be reduced by slow administration. A recent study reported that 80% of men experienced pain of moderate severity following an injection of TU. This pain peaked immediately after injection and lasted no longer than 1 — 2 days, returning to baseline on day 4. These results correspond with previous evidence suggesting that local irritation does not typically last longer than 3 days. No patients voluntarily discontinued TU therapy as a result of injection-site pain or local discomfort. Increase in PSA and prostate size was within the normal range. Though several studies have demonstrated an increased PSA velocity, in comparative studies, PSA values and prostate size were not higher for TU than for other testosterone therapies. As with any testosterone replacement therapy, serum PSA, prostate size and erythropoiesis parameters should be monitored in men aged > 45 years at quarterly intervals for the first year and then annually throughout the duration of therapy [35]. Side effects such as gynecomastia, breast tenderness and acne were reported in a minority of patients on TU. These side effects are not unique to TU therapy and occur more frequently among patients receiving other testosterone therapies. The relative absence of side effects in TUtreated patients is thought to be due to TU’s ability to improve and maintain normal physiological levels of T, DHT and estradiol. TE in contrast to TU commonly causes fluxes of supra- and subphysiological peaks shortly after and before injections. This flux often leads to mood swings and emotional imbalance, as well as elevated hematocrit levels. Increases of hematological parameters to eugonadal levels were seen in several studies of TU, but there was no occurrence of polycythemia, as observed in studies with traditional testosterone esters. Though rare, TU has been associated with reports of pulmonary oily microembolism (POME), causing symptoms such as the urge to cough and respiratory distress. POME is probably due to the improper injection of TU, in which the drug was injected too quickly, rather than due to TU itself. Current recommendations call for patients to receive TU in the clinic to avoid potential injection reactions. In the US clinical trials of TU, which included approximately 500 patients, there was one report of POME in a patient receiving a 750-mg dose of TU. The symptoms resolved within a few minutes and the patient did not need further medical attention. Instances of POME have also been reported since TU’s approval in Europe, though they were associated with a larger dose (1000 mg). Side effects beyond a shortness of breath due to POME include dizziness, flushing and rare instances of fainting. Due to the rare instances of POME, TU has not been readily approved in the US and is facing further scrutiny by regulatory authorities, despite its European approval in 2003.
Expert opinion

Testosterone modalities are differentiated by their route of administration, ability to maintain stable physiological levels of testosterone, safety profile, and dosing schedule convenience. Testosterone therapy is successful at reversing many of the symptoms associated with hypogonadism in both younger and older men (Table 3). As the majority of hypogonadal men require lifelong treatment with testosterone, it is important to utilize a therapy that is effective, safe, and convenient to use. A variety of testosterone replacement modalities are available today, though each modality has inherent deficiencies (Table 1). The shortcomings of testosterone esters are abundantly clear, as these injections do not provide physiological testosterone levels and require frequent administration. Testosterone gels are widely prescribed due to their favorable pharmacokinetic profile and positive long-term clinical results. Testosterone gels, however, require daily administration, which some patients find cumbersome. Additionally, testosterone gels have received a black box warning due to the potential risk of transference of unabsorbed gel from the patient to their spouse or young children. TU, by contrast, is administered only four times annually, produces stable levels of testosterone, and thus far has an excellent safety profile. From the standpoint of a physician, testosterone gel and TU are pharmacokinetically very similar in their ability to produce physiological levels of testosterone. Patients, however, may prefer the convenient dosing schedule of TU, which may lead to better compliance and therapeutic benefit. Initial consensus regarding restricting use of TU in older hypogonadal men due to the increased potential risks of polycythemia and prostate-related adverse effects have not been substantiated in long-term studies. No events of polycythemia have been recorded with TU administration; indeed, polycythemia is much more common with administration Table 3. Clinically significant outcomes of testosterone therapy. Improvements Complications ” Strength and muscle mass ” PSA and prostate volume ” Sense of well-being Lipid abnormalities #HDL ” Hemoglobin levels ” Risk of infertility ” Lean body mass Acne or oily skin Normal virilization Testicular atrophy # Overall body fat Skin reactions ” Sexual activity Gynecomastia ” Energy Polycythemia ” Libido Sleep apnea Testosterone undecanoate 2104 Expert Opin. Pharmacother. (2010) 11(12) Expert Opin. Pharmacother. Downloaded from informahealthcare.com by JHU John Hopkins University on 10/14/14 For personal use only. of traditional esters. Though no serious side effects have been noted with TU, there are still unquantified risks in terms of its impact on prostate size and potential cancer development, though these risks apply to all testosterone therapies. Careful scrutiny of patients experiencing episodes of POME following injection of TU is recommended since the precise cause of POME is not yet fully understood. Studies using TU did raise PSA levels and increased prostate size; however, these levels were well within the normal range and were not increased preferentially more than other testosterone modalities. It is strongly recommended that standard practice clinical guidelines for monitoring elderly patients be closely followed in elderly men receiving TU. Consideration should also be given to initially administer T-gel to new elderly patients, allowing for the monitoring of potential adverse reactions to testosterone replacement, especially considering the potential for effects on prostate health. After an initial monitoring period proves successful, patients may be transitioned to TU. Younger patients with little risk of prostate issues can be started on TU right away. TU can be taken every 3 months (after two loading doses), representing a significant convenience to patients. Positive clinical symptoms and stable trough plasma T levels measured before subsequent injections may enable the extension of the injection interval to 13 — 14 weeks, clearly a desirable result from the patient’s perspective. TU produces a modest maximal T concentration that has a gradual decline, thereby reducing the untoward side effects often seen with other esters. Clinical investigations of TU have shown that testosterone levels are maintained within the normal range for 12 weeks with one injection. Patients report fewer mood swings and more stable levels of energy and libido with TU compared with TE. Furthermore, TU requires only four injections per year compared with 26 injections per year of TE (if taken at a dose of 200 or 250 mg every 2 weeks). In addition to the favorable kinetic profile, TU is efficacious in improving LBM, hematological parameters, and mood. No serious side effects have been noted with the use of TU, including longterm data on patients treated with TU over 8 years. TU is both a desirable and safe option for the treatment of young hypogonadal men. Patients will benefit from the stable testosterone levels and fewer required injections, while achieving the desired benefits of androgen replacement.