Can Flomax (tamsulosin) be given at a dose of 0.8mg?

Tamsulosin Dosing at 0.8mg

Yes, Flomax (tamsulosin) can be given at a dose of 0.8mg once daily for patients who fail to respond to the 0.4mg dose after 2-4 weeks of treatment. 1

FDA-Approved Dosing Guidelines

The FDA-approved dosing for tamsulosin follows a step-wise approach:

1. Initial dose: 0.4mg once daily, taken approximately 30 minutes after the same meal each day
2. Dose adjustment: For patients who fail to respond to the 0.4mg dose after 2-4 weeks, the dose can be increased to 0.8mg once daily 1
3. Interruption of therapy: If treatment is discontinued or interrupted for several days at either dose, therapy should be restarted with the 0.4mg once-daily dose 1

Efficacy Considerations

Clinical research supports the use of the 0.8mg dose:

• Studies show that tamsulosin at 0.8mg provides additional symptom improvement compared to 0.4mg, with the weighted mean difference for Boyarsky symptom score showing a 16% improvement at 0.8mg versus 12% improvement at 0.4mg when compared to placebo 2
• The peak urine flow rate improvement is similar between 0.4mg and 0.8mg doses (both showing approximately 1.1 mL/sec improvement over placebo) 2

Safety Considerations

When increasing to the 0.8mg dose, be aware of:

• Increased adverse effects: The frequency of adverse effects increases substantially at the 0.8mg dose, with up to 75% of patients reporting adverse events at this dosage compared to lower rates with the 0.4mg dose 2
• Higher discontinuation rate: Discontinuation rates increase to approximately 16% with the 0.8mg dose compared to rates similar to placebo with the 0.4mg dose 2
• Common adverse effects: The most frequently reported adverse events include dizziness, rhinitis, and abnormal ejaculation 3

Important Precautions

• Tamsulosin capsules should not be crushed, chewed, or opened 1
• Tamsulosin 0.4mg should not be used in combination with strong inhibitors of CYP3A4 (e.g., ketoconazole) 1
• Monitor for orthostatic hypotension, especially when initiating therapy or increasing the dose

Clinical Decision Algorithm

1. Start with tamsulosin 0.4mg once daily for 2-4 weeks
2. Assess response:
   • If adequate symptom improvement → continue 0.4mg dose
   • If inadequate symptom improvement → increase to 0.8mg once daily
3. If adverse effects become intolerable after dose increase:
   • Return to 0.4mg dose
   • Consider alternative therapy if symptoms remain inadequately controlled

In conclusion, while the 0.8mg dose of tamsulosin is FDA-approved and can provide additional symptom relief for some patients, clinicians should carefully weigh the modest additional efficacy against the substantially increased risk of adverse effects when considering this higher dose.