AXIRON
Clinical safety rating: caution
Comprehensive clinical and safety monograph for AXIRON (AXIRON).
Testosterone replacement therapy; binds to androgen receptors, modulating gene expression and promoting protein synthesis, muscle growth, and secondary sexual characteristics.
| Metabolism | Primarily hepatic via CYP3A4 and CYP2B6; also metabolized via 5α-reductase to dihydrotestosterone and aromatase to estradiol. |
| Excretion | Testosterone is primarily excreted in urine as glucuronide and sulfate conjugates (about 90%) and about 6% in feces via bile. Approximately 90% of a dose is excreted in urine, with the remainder in feces. |
| Half-life | The terminal elimination half-life of testosterone is approximately 10-100 minutes after intravenous injection, but for Axiron (testosterone topical solution), the apparent half-life is about 1-2 hours due to continued absorption from the skin and distribution/elimination. Clinically, steady state is achieved after about 2 weeks of daily application. |
| Protein binding | Testosterone is extensively bound to plasma proteins: approximately 98% bound, primarily to sex hormone-binding globulin (SHBG) (about 40-60%) and albumin (about 40-60%). |
| Volume of Distribution | The apparent volume of distribution (Vd) of testosterone is approximately 1.0 L/kg. This large Vd indicates extensive distribution into tissues, including muscle and fat. |
| Bioavailability | The absolute bioavailability of testosterone from Axiron compared to intravenous administration is approximately 10-20% based on serum concentration data, with significant interindividual variability due to skin absorption differences. |
| Onset of Action | After topical application of Axiron, serum testosterone levels rise within 30 minutes, reaching peak concentrations at approximately 2-4 hours after application. |
| Duration of Action | With daily application of Axiron, serum testosterone concentrations are maintained within the normal range over a 24-hour dosing interval. The duration is dependent on regular daily use; missing doses results in gradual decline. |
One or two pump actuations (30 mg per actuation) applied to the axilla once daily; dose range 30-90 mg daily.
| Dosage form | SOLUTION, METERED |
| Renal impairment | No dose adjustment required. |
| Liver impairment | No dose adjustment required. |
| Pediatric use | Not indicated for use in pediatric patients. |
| Geriatric use | No specific dose adjustment; use lower end of dosing range due to potential comorbidities. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for AXIRON (AXIRON).
| Breastfeeding | Testosterone is excreted into human milk with an estimated M/P ratio of approximately 0.2-0.4 based on limited data. Exogenous testosterone may suppress lactation and cause virilization in the infant. AXIRON is not recommended during breastfeeding. If unavoidable, the infant should be monitored for signs of androgen excess (e.g., genital enlargement, premature adrenarche). |
| Teratogenic Risk | AXIRON (testosterone) is contraindicated in pregnancy. Testosterone is an androgenic hormone that can cause virilization of the female fetus if exposed during the first trimester (critical period for sexual differentiation). In the second and third trimesters, exposure may lead to clitoromegaly, labial fusion, and other masculinizing effects. There is a risk of spontaneous abortion and fetal harm throughout gestation. Use is not recommended at any stage of pregnancy. |
■ FDA Black Box Warning
Blood pressure increases have been reported; testosterone products may increase risk of cardiovascular events. WARNING: Secondary exposure to children can cause premature virilization.
| Serious Effects |
["Known hypersensitivity to testosterone or components","Breast cancer in males","Prostate cancer suspected or confirmed","Pregnancy or nursing women (virilization of fetus/infant)","Severe urinary tract obstruction (e.g., from BPH)"]
| Precautions | ["May cause polycythemia, worsening of sleep apnea, and benign prostatic hyperplasia (BPH) symptoms.","Edema in patients with preexisting cardiac, renal, or hepatic disease.","Gynecomastia, hypercalcemia, and decreased spermatogenesis.","Not indicated for non-hypogonadal conditions."] |
| Food/Dietary | No significant food interactions. Grapefruit and grapefruit juice do not interact with topical testosterone. Alcohol consumption may increase risk of adverse effects such as hypertension; moderation advised. |
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| Fetal Monitoring | If accidental exposure occurs during pregnancy, monitor fetal growth and development with serial ultrasound assessments, including detailed anatomy scan and assessment of fetal genitalia. Maternal monitoring of serum testosterone levels may be considered, though therapeutic range is not established in pregnancy. No specific fetal monitoring is indicated if exposure is avoided. |
| Fertility Effects | Exogenous testosterone can suppress gonadotropin (LH, FSH) secretion, leading to oligospermia or azoospermia and reduced fertility in males. In females, testosterone may disrupt ovulatory function and menstrual cycles. Effects are generally reversible upon discontinuation. AXIRON should not be used in individuals attempting conception unless specifically indicated. |
| Clinical Pearls | AXIRON (testosterone topical solution) should be applied to the axilla only; allow to dry before dressing to avoid transfer. Monitor hematocrit and prostate-specific antigen (PSA) at baseline and periodically. Avoid use in men with breast cancer or known or suspected prostate cancer. Can cause virilization in women if transferred via skin contact. |
| Patient Advice | Apply AXIRON to the armpit only, using the applicator; do not apply to other body parts. · Allow the solution to dry completely before putting on clothing to prevent transfer to others. · Wash hands thoroughly after application and cover the application site with clothing. · Keep children and women away from the application site to avoid accidental exposure. · Do not shower or swim for at least 2 hours after application. · Report symptoms of excessively high testosterone such as nausea, vomiting, changes in skin color, or ankle swelling. |