Drug interactions between Bactrim DS and rifampin
| Results for the following 2 drugs: |
|---|
| Bactrim DS (sulfamethoxazole/trimethoprim) |
| rifampin |
Interactions between your selected drugs
rifampin ↔ sulfamethoxazole
Applies to:rifampin and Bactrim DS (sulfamethoxazole/trimethoprim)
MONITOR: During coadministration of rifampin and sulfamethoxazole-trimethoprim (SMX-TMP), the serum concentrations of rifampin may be increased while those of SMX and TMP may be decreased. In a study of 15 tuberculosis patients treated with rifampin for at least two weeks, SMX-TMP given for 5 to 10 days increased the median peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of rifampin by 31% and 60%, respectively. The mechanism of interaction has not been established. In another study of 10 HIV-infected patients receiving SMX-TMP prophylaxis (800 mg-160 mg orally once a day) for at least one month, antituberculosis therapy containing rifampin (600 mg/day) given for more than 12 days decreased the mean AUC of SMX by 23% and that of TMP by 47%, most likely due to induction of hepatic microsomal enzymes by rifampin. The clinical significance of this interaction is unknown but may be greater with low dosages of SMX-TMP. A case-control study evaluating the effect of SMX-TMP dosage on the risk of toxoplasmosis suggest that rifampin exposure may reduce the efficacy of SMX-TMP prophylaxis.
MANAGEMENT: Patients receiving rifampin and SMX-TMP should be monitored for potentially increased toxicity of rifampin. Patients should be advised to notify their physician if they experience signs and symptoms of hepatotoxicity such as fever, rash, anorexia, nausea, vomiting, fatigue, right upper quadrant pain, dark urine, and jaundice. In addition, the possibility of reduced efficacy of SMX-TMP should be considered, particularly when used for prevention of toxoplasmic encephalitis in HIV patients because adequate drug levels are required in the central nervous system. It may be advisable to refrain from low-dose prophylactic regimens (less than 4 DS tablets per week).
rifampin ↔ trimethoprim
Applies to:rifampin and Bactrim DS (sulfamethoxazole/trimethoprim)
MONITOR: During coadministration of rifampin and sulfamethoxazole-trimethoprim (SMX-TMP), the serum concentrations of rifampin may be increased while those of SMX and TMP may be decreased. In a study of 15 tuberculosis patients treated with rifampin for at least two weeks, SMX-TMP given for 5 to 10 days increased the median peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of rifampin by 31% and 60%, respectively. The mechanism of interaction has not been established. In another study of 10 HIV-infected patients receiving SMX-TMP prophylaxis (800 mg-160 mg orally once a day) for at least one month, antituberculosis therapy containing rifampin (600 mg/day) given for more than 12 days decreased the mean AUC of SMX by 23% and that of TMP by 47%, most likely due to induction of hepatic microsomal enzymes by rifampin. The clinical significance of this interaction is unknown but may be greater with low dosages of SMX-TMP. A case-control study evaluating the effect of SMX-TMP dosage on the risk of toxoplasmosis suggest that rifampin exposure may reduce the efficacy of SMX-TMP prophylaxis.
MANAGEMENT: Patients receiving rifampin and SMX-TMP should be monitored for potentially increased toxicity of rifampin. Patients should be advised to notify their physician if they experience signs and symptoms of hepatotoxicity such as fever, rash, anorexia, nausea, vomiting, fatigue, right upper quadrant pain, dark urine, and jaundice. In addition, the possibility of reduced efficacy of SMX-TMP should be considered, particularly when used for prevention of toxoplasmic encephalitis in HIV patients because adequate drug levels are required in the central nervous system. It may be advisable to refrain from low-dose prophylactic regimens (less than 4 DS tablets per week).
See also...
Drug Interaction Classification
The classifications below are a guideline only. The relevance of a particular drug interaction to a specific patient is difficult to determine using this tool alone given the large number of variables that may apply.
| Major | Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit. |
| Moderate | Moderately clinically significant. Usually avoid combinations; use it only under special circumstances. |
| Minor | Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan. |
Do not stop taking any medications without consulting your healthcare provider.
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