From the FDA Drug Label
During administration of 800 mg sulfamethoxazole and 160 mg trimethoprim b.i.d., the mean steady-state plasma concentration of trimethoprim was 1.72 μg/mL. The dosage comparison between Septra (Trimethoprim/Sulfamethoxazole) 400/80 mg and double strength 800/160 mg is a 1:2 ratio, with the double strength being twice the dose of the regular strength 1. Key points:
- The double strength Septra contains 800 mg of sulfamethoxazole and 160 mg of trimethoprim.
- The regular strength Septra contains 400 mg of sulfamethoxazole and 80 mg of trimethoprim.
- The double strength is administered twice a day (b.i.d.), which is the same administration frequency as the regular strength, but with twice the dose.
From the Research
Septra (Trimethoprim/Sulfamethoxazole) 800/160 mg double strength tablets are exactly twice the active ingredients as the regular strength 400/80 mg tablets, making one double strength tablet equivalent to taking two regular strength tablets. The regular strength tablet contains 400 mg of sulfamethoxazole and 80 mg of trimethoprim, while the double strength tablet contains 800 mg of sulfamethoxazole and 160 mg of trimethoprim. This is an important consideration when dosing, as it affects the number of pills needed and potentially improves medication adherence 2.
Key Considerations
- The double strength formulation is often preferred for adult dosing as it reduces the number of pills needed, potentially improving medication adherence.
- However, the regular strength tablets may be more appropriate for patients requiring dose adjustments, such as those with renal impairment or for pediatric dosing where more precise increments are needed.
- Both formulations contain the same medication in the same 5:1 ratio of sulfamethoxazole to trimethoprim, which work synergistically to block two consecutive steps in bacterial folate synthesis, enhancing their antimicrobial effectiveness 3, 4.
Clinical Implications
- In patients with renal impairment, the dosage of Septra may need to be adjusted to prevent accumulation of the drug and potential toxicity 5.
- The use of Septra can be associated with rare but serious adverse effects, such as transient psychosis, especially in immune-competent patients 6.
- When prescribing Septra, it is essential to consider the patient's renal function, age, and potential for adverse effects to ensure safe and effective treatment.
Dosage Comparison
- One double strength tablet is equivalent to two regular strength tablets, which is crucial for dosing considerations and medication adherence.
- The choice between regular and double strength tablets should be based on individual patient needs, including renal function, age, and the potential for adverse effects.