testosterone: clinical use

Prescribing considerations

• Confirm compatible clinical features and biochemical deficiency on two separate measurements; investigate alternative causes.
• Assess prostate and breast disease, cardiovascular or thrombotic risk, hypertension, sleep apnoea, fertility plans and ability to follow transfer precautions.
• Use caution with severe cardiac, hepatic or renal disease, ischaemic heart disease, thrombophilia, epilepsy, migraine and cancer-associated hypercalcaemia.
• Explain that exogenous testosterone can reversibly suppress spermatogenesis.

Contraindications and cautions

• Known or suspected prostate carcinoma
• Known or suspected breast carcinoma
• Hypersensitivity to testosterone or formulation excipients

Monitoring

• Use product-specific timing for testosterone sampling and avoid gel contamination of the blood-taking site.
• Monitor clinical response, testosterone, haemoglobin, haematocrit, red-cell count, blood pressure, prostate assessment and PSA as appropriate.
• Consider liver function and lipid monitoring; monitor glucose and HbA1c in diabetes and calcium where bone metastases create hypercalcaemia risk.
• Review urgently if erythrocytosis, significant oedema, thrombotic symptoms, severe skin reactions or excessive androgen effects occur.

Clinical pharmacology

Transdermal testosterone enters the systemic circulation through the skin. It acts through androgen receptors and conversion to dihydrotestosterone and oestradiol; skin absorption and sampling requirements vary by formulation.

Formulation and product differences

• Tostran uses a metered pump and is rubbed gently onto the abdomen or inner thighs.
• Testogel is available in pump and sachet presentations; selected current products are spread over the shoulders or upper arms without rubbing.
• Application sites, pump-priming steps and minimum times before washing or contact differ, so products should not be treated as directly interchangeable.

Gel

Route: Cutaneous

Strengths: 16.2 mg/g

Sachet

Route: Oral

Strengths: 40.5 mg

Transdermal gel

Route: Transdermal

Strengths: 20 mg/g