Testosterone

Usage

• Testosterone is prescribed for conditions associated with testosterone deficiency or absence of endogenous testosterone in males. This includes:
  • Primary hypogonadism: Testicular failure due to various causes (e.g., cryptorchidism, bilateral torsion, orchitis).
  • Hypogonadotropic hypogonadism: Deficiency or impairment of gonadotropin or LHRH, often due to pituitary-hypothalamic injury.
  • Delayed puberty in adolescent males (specific formulations).
• Pharmacological classification: Androgen, anabolic steroid.
• Mechanism of Action: Testosterone acts as an endogenous androgen, binding to androgen receptors in target tissues. This promotes the growth and development of male sex organs, maintains secondary sexual characteristics, and exerts anabolic effects on bone and muscle. It also influences erythropoiesis and libido.

Alternate Names

• No official alternate generic names.
• Brand names: Examples include Testogel, Tostran, Testavan, Sustanon, Nebido, Aveed, Delatestryl, Testopel, Jatenzo, Kyzatrex. (Note: Brand availability varies by region.)

How It Works

• Pharmacodynamics: Testosterone binds to intracellular androgen receptors, influencing gene expression and protein synthesis. This leads to the development and maintenance of male secondary sexual characteristics (muscle mass, bone density, hair growth), stimulates erythropoiesis, and affects libido and sexual function.
• Pharmacokinetics:
  • Absorption: Varies depending on the route of administration (intramuscular, transdermal, subcutaneous implant). Oral testosterone undergoes significant first-pass metabolism and is generally not preferred.
  • Metabolism: Primarily hepatic, involving conversion to dihydrotestosterone (DHT) and estradiol.
  • Elimination: Excreted primarily in urine, with a small portion in feces.

Dosage

Standard Dosage

Adults:

• Dosage and administration route vary widely based on the specific formulation (gel, injection, implant, oral).
• Intramuscular injections:
  • Testosterone cypionate/enanthate: 50-400 mg every 2-4 weeks.
  • Testosterone undecanoate (Nebido): 1000 mg every 10-14 weeks (initial interval of 6 weeks).
  • Sustanon 250: 250 mg every 3 weeks, or 100-200 mg every 2 weeks.
• Transdermal gels: Dosage varies by brand; typically applied daily.
• Subcutaneous implants: Dose depends on the number and size of pellets implanted (typically every 3-6 months).
• Oral: Less commonly used; dosage varies by brand.

Children:

• Use and dose must be determined by a specialist and is generally reserved for delayed puberty in adolescent males. Pediatric dosing guidelines are not standardized.

Special Cases:

• Elderly Patients: Start with lower doses and titrate cautiously.
• Patients with Renal Impairment: Use with caution. Dose adjustments may be required, especially for injectable formulations.
• Patients with Hepatic Dysfunction: Use with caution, especially for oral formulations, as these undergo hepatic metabolism. Transdermal application may be preferred in these patients.
• Patients with Comorbid Conditions: Careful monitoring and dose adjustments may be necessary for patients with conditions like diabetes, cardiovascular disease, or obstructive sleep apnea.

Clinical Use Cases

Dosage recommendations for specific clinical use cases are not standardized and are determined based on patient needs.

• Intubation: No specific dosage recommendations.
• Surgical Procedures: Perioperative testosterone administration has been investigated but is not routinely recommended with established guidelines.
• Mechanical Ventilation: Testosterone has been used in research settings for patients with prolonged mechanical ventilation to counteract muscle wasting, but no standardized dosing guidelines exist.
• Intensive Care Unit (ICU) Use: Similar to mechanical ventilation, testosterone has been explored to address muscle wasting, but established guidelines are lacking.
• Emergency Situations: No specific role for testosterone in emergency situations.

Dosage Adjustments

• Dose adjustments are based on serum testosterone levels, clinical response, and the presence of adverse effects.

Side Effects

Common Side Effects

• Application site reactions (with gels and patches).
• Gynecomastia.
• Prostate enlargement.
• Acne.
• Mood changes.
• Polycythemia.

Rare but Serious Side Effects

• Venous thromboembolism.
• Sleep apnea.
• Hepatotoxicity (with oral formulations).

Long-Term Effects

• Potential for prostate cancer progression (in susceptible individuals).
• Cardiovascular risks.

Adverse Drug Reactions (ADR)

• Severe allergic reactions (rare).

Contraindications

• Prostate cancer.
• Male breast cancer.
• Severe liver disease.
• History of liver tumors.

Drug Interactions

• Insulin or other antidiabetic medications.
• Anticoagulants (e.g., warfarin).
• Corticosteroids.

Pregnancy and Breastfeeding

• Pregnancy Category X: Contraindicated in pregnancy. Testosterone can cause virilization of the female fetus.
• Breastfeeding: Testosterone is excreted in breast milk and can affect the nursing infant. Breastfeeding is not recommended.

Drug Profile Summary

• Mechanism of Action: Binds to androgen receptors, promoting male sexual development and function.
• Side Effects: Acne, gynecomastia, prostate enlargement, mood changes, polycythemia.
• Contraindications: Prostate cancer, male breast cancer, severe liver disease.
• Drug Interactions: Antidiabetic drugs, anticoagulants, corticosteroids.
• Pregnancy & Breastfeeding: Contraindicated.
• Dosage: Highly variable based on formulation and patient characteristics.
• Monitoring Parameters: Serum testosterone levels, prostate-specific antigen (PSA), liver function tests, complete blood count.

Popular Combinations

Information on popular combinations is limited. Sometimes combined with other medications to manage specific symptoms or side effects associated with hypogonadism.

Precautions

• Careful patient selection and monitoring are essential.
• Pre-screening for prostate cancer is crucial.
• Monitor for cardiovascular and liver-related adverse effects.
• Advise patients about potential drug interactions.

FAQs (Frequently Asked Questions)

Q1: What is the recommended dosage for Testosterone?

A: Testosterone dosage is highly variable depending on the formulation, indication, patient age, and response. Intramuscular injections range from 50-400 mg every 2-4 weeks (cypionate/enanthate) to 1000mg every 10-14 weeks (undecanoate). Transdermal gels are typically applied daily, while pellet implants last 3-6 months. Oral formulations are less commonly used.

Q2: What are the primary indications for testosterone therapy?

A: The primary indication is male hypogonadism (both primary and secondary), confirmed by clinical symptoms and low serum testosterone levels.

Q3: What are the common side effects of testosterone therapy?

A: Common side effects include acne, gynecomastia, prostate enlargement, increased red blood cell count, mood changes, and application site reactions (with gels and patches).

Q4: How should testosterone levels be monitored during therapy?

A: Regular monitoring of serum testosterone levels is essential. The timing of blood draws should be standardized (e.g., morning) and tailored to the specific formulation.

Q5: What are the contraindications to testosterone therapy?

A: Contraindications include prostate cancer, male breast cancer, severe liver disease, and a history of liver tumors.

Q6: Can testosterone be used in women?

A: Testosterone is not FDA-approved for use in women. Off-label use may occur in specific circumstances under the supervision of a specialist. However, there are potential virilizing effects.

Q7: Is testosterone safe to use in patients with heart disease?

A: Testosterone’s effects on cardiovascular health are complex and not fully understood. Some studies suggest potential benefits, while others raise concerns. Careful cardiovascular risk assessment and monitoring are necessary.

Q8: Are there any dietary considerations while taking testosterone?

A: No specific dietary restrictions are universally recommended, but maintaining a healthy diet and lifestyle are generally advised in conjunction with testosterone therapy.

Q9: What are the different formulations of testosterone available?

A: Available formulations include intramuscular injections, transdermal gels, subcutaneous implants, buccal patches, and oral capsules. The choice of formulation depends on patient preference, tolerability, and clinical factors.

Q10: What should be done if a patient misses a dose of testosterone?

A: The course of action for a missed dose depends on the formulation. For injectable formulations, the patient should contact their healthcare provider for instructions. For daily applications of gels, the missed dose should be applied as soon as remembered, unless it is almost time for the next dose.