Testogel pump and sachets are both widely prescribed testosterone replacement therapies in the UK, but they differ in concentration, delivery method and dosing flexibility. The pump (16.2 mg/g) delivers metered doses of 20.25 mg per actuation, whilst sachets (1% gel) provide fixed doses of 25 mg or 50 mg. Because these formulations are not directly equivalent on a milligram-for-milligram basis, switching between them requires careful dose adjustment and monitoring. Understanding these differences is essential for healthcare professionals and patients to ensure safe, effective treatment of hypogonadism and optimal therapeutic outcomes.

Understanding Testogel Pump and Equivalent Formulations

Testogel is a widely prescribed testosterone replacement therapy (TRT) available in the UK for men with confirmed hypogonadism. The product comes in two primary formulations: multi-dose pump dispensers and single-dose sachets. Both contain testosterone gel as the active ingredient but differ in concentration, delivery mechanism and dosing flexibility.

The Testogel pump (Testogel 16.2 mg/g gel in a canister) delivers a metered dose with each actuation. One full pump actuation dispenses approximately 1.25 g of gel, containing 20.25 mg of testosterone. This formulation allows for dose titration in increments of 20.25 mg and is particularly convenient for patients requiring stable, long-term therapy. The pump is designed to deliver up to 60 actuations per canister.

In contrast, Testogel sachets are available as a 1% gel in pre-measured doses of 25 mg (2.5 g gel) or 50 mg (5 g gel) of testosterone per sachet. Each sachet contains a fixed amount of gel that is applied once daily. Whilst sachets offer simplicity and portability, they provide less flexibility for dose adjustment compared to the pump, with titration limited to 25 mg increments.

Equivalence between these formulations is a common clinical question. Because the pump (16.2 mg/g) and sachets (1% = 10 mg/g) differ in concentration, direct milligram-for-milligram substitution is not appropriate. Instead, both products should be titrated individually to achieve serum testosterone levels within the normal physiological range, guided by the Summary of Product Characteristics (SmPC) for each formulation. The choice between pump and sachet often depends on patient preference, lifestyle factors and the prescriber's assessment of adherence and dose stability. Understanding these formulation differences is essential for both patients and healthcare professionals to ensure optimal therapeutic outcomes and patient satisfaction with TRT.

Comparing Testogel Pump Doses to Gel Sachets

Dose conversion between Testogel pump and sachets requires careful consideration, as the two formulations differ in concentration and are not directly interchangeable on a milligram-for-milligram basis. Each product should be dosed according to its own SmPC, with subsequent titration based on serum testosterone levels and clinical response.

For the Testogel 16.2 mg/g pump, the usual starting dose is 40.5 mg of testosterone daily (2 pump actuations). Depending on clinical response and serum testosterone levels, the dose may be adjusted in increments of 20.25 mg (1 actuation), up to a maximum of 81 mg daily (4 actuations). Partial actuations should not be used; if dose adjustment is needed between whole actuations, consider alternating daily totals (e.g., 2 and 3 actuations on alternate days) pending review, or switching to the sachet formulation for finer control.

For Testogel 1% sachets, the usual starting dose is 50 mg of testosterone daily (one 50 mg sachet). The dose may be adjusted to 25 mg daily (one 25 mg sachet) or increased to 75 mg or 100 mg daily (using combinations of sachets), based on serum testosterone levels measured at steady state. Sachets offer titration in 25 mg steps, which may suit some patients better than the pump's 20.25 mg increments.

Application technique is important and differs slightly between formulations. The 16.2 mg/g pump gel should be applied to clean, dry, intact skin on the shoulders and upper arms only. The 1% sachet gel may be applied to the shoulders, upper arms or abdomen (avoiding the genital area). For both formulations, the gel should be spread thinly and allowed to dry for 3–5 minutes before dressing. Wash your hands thoroughly with soap and water immediately after application. Cover the application site with clothing once dry. To reduce the risk of transfer to others, particularly women and children, avoid skin-to-skin contact until the gel has dried, and wash the application site with soap and water before any anticipated close contact.

Washing and bathing intervals also differ: for the 16.2 mg/g pump, showering or bathing may be permitted 2 hours after application, whereas for the 1% sachets, a longer interval of 6 hours is recommended. Always follow the specific instructions in the patient information leaflet for your formulation.

Healthcare professionals should provide clear written instructions when switching between formulations, ensuring patients understand that dosing is not directly equivalent and that proper application technique must be followed to maintain stable testosterone levels.

Switching Between Testosterone Replacement Products

Switching between testosterone formulations—whether from pump to sachet, sachet to pump or to entirely different TRT products—is a common occurrence in clinical practice. Reasons for switching may include patient preference, side effects, supply issues or inadequate therapeutic response.

When transitioning between Testogel pump and sachets, a direct milligram-for-milligram switch is not recommended because the formulations differ in concentration and pharmacokinetic profile. Instead, initiate the new formulation at its recommended starting dose as per the SmPC (e.g., 40.5 mg daily for the 16.2 mg/g pump; 50 mg daily for the 1% sachets), then retitrate based on serum testosterone levels and clinical symptoms. This approach ensures safe and effective dosing and avoids the risk of under- or over-replacement.

Switching to alternative TRT formulations requires careful consideration. UK-available options include:

• Tostran 2% gel or Testavan 2% gel: Alternative transdermal gels with different application sites and dosing schedules

• Testosterone injections (e.g., Sustanon, Nebido): Provide longer-lasting effect but with more variable serum levels and different monitoring requirements

• Testosterone patches: Offer steady delivery but may cause skin irritation

Each formulation has distinct pharmacokinetics, application methods and monitoring needs. Consult the relevant SmPC and consider specialist advice when switching between different classes of TRT.

Monitoring during transitions is essential. Check serum testosterone levels approximately 2–3 months after any dose or formulation change. Sampling should be performed at a consistent time of day and, for transdermal gels, follow the timing recommended in the product SmPC or by your local laboratory (some protocols recommend sampling 2–4 hours after gel application to assess peak levels; others recommend trough levels). Target testosterone levels should be in the normal physiological range for adult men (typically 10–30 nmol/L, though local laboratory reference ranges may vary). Adjust the dose as needed to achieve target levels and symptom control.

Patients should be counselled that it may take several weeks for serum levels to stabilise after switching formulations. They should report any symptoms of hypogonadism (fatigue, reduced libido, mood changes) or over-replacement (acne, aggression, fluid retention, ankle swelling) promptly to their healthcare provider. If you experience any side effects, talk to your doctor or pharmacist. You can also report suspected side effects via the MHRA Yellow Card scheme at www.mhra.gov.uk/yellowcard or search for 'Yellow Card' in the Google Play or Apple App Store.

Therapeutic Equivalence and Clinical Effectiveness

Therapeutic equivalence in testosterone replacement therapy means that different formulations, when titrated appropriately, can achieve similar serum testosterone levels and clinical outcomes. Whilst the Testogel pump (16.2 mg/g) and sachets (1%) are not bioequivalent on a milligram-for-milligram basis due to differences in concentration and formulation, both are effective when dosed according to their respective SmPCs and titrated to target serum testosterone levels.

Regulatory approval by the Medicines and Healthcare products Regulatory Agency (MHRA) and the European Medicines Agency (EMA) requires manufacturers to demonstrate the safety, quality and efficacy of each formulation through rigorous clinical trials. Both Testogel formulations have been shown to restore serum testosterone to physiological levels in men with hypogonadism, meaning patients can expect similar clinical outcomes when the dose is appropriately individualised.

Clinical effectiveness, however, extends beyond achieving target testosterone levels. Real-world factors influencing therapeutic success include:

• Patient adherence: Pump formulations may improve compliance in some patients due to convenience, whilst others prefer the simplicity and portability of sachets

• Application technique: Inconsistent application, incorrect site selection or premature washing can reduce absorption with either formulation

• Skin characteristics: Individual variation in skin permeability may affect absorption rates

• Lifestyle factors: Physical activity, sweating and bathing habits can influence gel effectiveness

Evidence from clinical practice suggests that both formulations are equally effective when used correctly and titrated to target levels. Patient preference, adherence patterns and tolerability appear to be more important determinants of long-term treatment success than the specific formulation chosen.

Healthcare professionals should reassure patients that switching between Testogel formulations will not compromise treatment effectiveness, provided the new formulation is started at the recommended dose, application technique is correct and serum testosterone levels are monitored and adjusted as needed.

Prescribing Considerations for Healthcare Professionals

Prescribing testosterone replacement therapy requires careful patient selection, appropriate baseline investigations and ongoing monitoring. NICE Clinical Knowledge Summaries (CKS) emphasise that TRT should only be initiated in men with confirmed biochemical hypogonadism (consistently low serum testosterone on two separate morning samples, taken at least one week apart) accompanied by relevant clinical symptoms such as reduced libido, erectile dysfunction, fatigue or loss of muscle mass.

Choosing between Testogel pump and sachets involves several practical considerations:

• Dose flexibility: Pumps allow titration in increments of 20.25 mg; sachets in 25 mg steps. Choose the formulation that best matches the patient's likely dose requirement

• Cost-effectiveness: Local formulary and pricing arrangements vary; consult your local guidelines

• Patient dexterity: Patients with arthritis or reduced manual dexterity may find sachets easier to open and apply

• Travel and portability: Sachets are more convenient for patients who travel frequently

• Application site preference: The 16.2 mg/g pump is applied to shoulders/upper arms only; the 1% sachets may also be applied to the abdomen

Safety monitoring is essential regardless of formulation. Healthcare professionals should:

• Check full blood count (FBC) and haematocrit at baseline, 3 months and at least annually thereafter. Testosterone can stimulate erythropoiesis, potentially causing polycythaemia. If haematocrit rises above 0.54 (54%), consider dose reduction or temporary discontinuation and investigate other causes

• Monitor prostate-specific antigen (PSA) and perform digital rectal examination in men over 40 (or younger if at increased risk) before starting TRT and periodically thereafter, in line with age-appropriate prostate cancer screening guidance. Investigate any significant rise in PSA or abnormal findings promptly

• Assess liver function at baseline and if clinically indicated

• Review cardiovascular risk factors. Counsel patients about the potential cardiovascular risks and benefits of TRT, and monitor blood pressure and lipid profile

• Monitor bone density in men with osteoporosis risk factors, as appropriate

• Measure serum testosterone at baseline (two samples), then at steady state (approximately 2–3 months after starting or changing dose), and periodically thereafter. Sampling should be at a consistent time of day, following the product SmPC or local laboratory protocol

Contraindications to TRT include:

• Known or suspected prostate cancer or male breast cancer

• Hypersensitivity to testosterone or any excipients

Cautions (use with care and increased monitoring) include:

• Untreated severe obstructive sleep apnoea

• Severe cardiac, hepatic or renal insufficiency

• History of, or risk factors for, venous thromboembolism

• Benign prostatic hyperplasia with significant lower urinary tract symptoms

• Hypertension

• Epilepsy or migraine

• Pre-existing polycythaemia or significant risk factors for erythrocytosis

Refer to the relevant SmPC for a full list of contraindications, cautions and drug interactions.

Patient counselling should cover:

• Proper application technique, including correct anatomical sites, hand washing after use and allowing the gel to dry before dressing

• Importance of avoiding skin-to-skin contact with others (especially women and children) until the gel has dried, and washing the application site before anticipated close contact

• Timing of washing/bathing relative to application (product-specific)

• Recognition of adverse effects (acne, mood changes, breast tenderness, ankle swelling, increased red blood cell count)

• When to seek urgent medical advice (chest pain, breathing difficulties, leg swelling or pain, prolonged erections)

• How to report side effects via the MHRA Yellow Card scheme

Prescribers should document the rationale for formulation choice and ensure patients receive clear written instructions, particularly when switching between products. Shared decision-making, considering patient preference alongside clinical factors, optimises adherence and treatment satisfaction with testosterone replacement therapy. Always consult the current SmPC, NICE CKS, British Society for Sexual Medicine (BSSM) guidelines and local formulary when prescribing TRT.

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