Drug interactions between Bactrim and Combivir
| Results for the following 2 drugs: |
|---|
| Bactrim (sulfamethoxazole/trimethoprim) |
| Combivir (lamivudine/zidovudine) |
Interactions between your selected drugs
zidovudine ↔ sulfamethoxazole
Applies to:Combivir (lamivudine/zidovudine) and Bactrim (sulfamethoxazole/trimethoprim)
Limited data indicate that zidovudine may significantly increase the serum half-life of both trimethoprim (TMP) and sulfamethoxazole (SMX). The mechanism is not known, but may be related to an increase in the volume of distribution of each drug. In addition, trimethoprim can decrease the renal clearance of zidovudine and its glucuronide metabolite by inhibiting their tubular secretion. However, net clearance is not affected because zidovudine is mostly metabolized and the glucuronide may be eliminated via biliary excretion. This interaction is not likely to be clinically important except when hepatic glucuronidation is also impaired by liver disease or drug inhibition.
Recommended management consists of monitoring for side effects of each drug and reducing dosages as necessary.
zidovudine ↔ trimethoprim
Applies to:Combivir (lamivudine/zidovudine) and Bactrim (sulfamethoxazole/trimethoprim)
Limited data indicate that zidovudine may significantly increase the serum half-life of both trimethoprim (TMP) and sulfamethoxazole (SMX). The mechanism is not known, but may be related to an increase in the volume of distribution of each drug. In addition, trimethoprim can decrease the renal clearance of zidovudine and its glucuronide metabolite by inhibiting their tubular secretion. However, net clearance is not affected because zidovudine is mostly metabolized and the glucuronide may be eliminated via biliary excretion. This interaction is not likely to be clinically important except when hepatic glucuronidation is also impaired by liver disease or drug inhibition.
Recommended management consists of monitoring for side effects of each drug and reducing dosages as necessary.
trimethoprim ↔ lamivudine
Applies to:Bactrim (sulfamethoxazole/trimethoprim) and Combivir (lamivudine/zidovudine)
In a study with 14 HIV-positive patients, coadministration of trimethoprim/sulfamethoxazole (TMP/SMX DS once a day for 5 days) and lamivudine (300 mg single dose on day 5) resulted in a mean decrease of 35% in lamivudine renal clearance and a mean increase of 43% in lamivudine area under the plasma concentration-time curve. The mechanism of interaction is thought to be competitive inhibition of tubular secretion by trimethoprim. Lamivudine did not affect the pharmacokinetic profile of TMP/SMX. Given the favorable safety profile of lamivudine, this interaction is unlikely to be of clinical significance. However, the effect of higher dosages of TMP/SMX on lamivudine pharmacokinetics has not been investigated.
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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