Pharmacokinetic Parameters of Co-trimoxazole
Pharmacokinetic Parameters of Co-trimoxazole
Rationale:

 Treatment of multidrug or extensively drug resistant tuberculosis (MDR/XDR-TB) is a real
 challenge as failure in response to treatment and serious side-effects are frequently
 encountered. New, more effective drugs with less side effects are therefore urgently needed
 to solve this problem. Although several new drugs against TB are in the pipeline, physicians
 currently have limited treatment options for treatment of complicated MDR/XDR-TB cases.
 Therefore, drugs developed and labeled for other infectious diseases are evaluated for TB.
 Co-trimoxazole consists of sulfamethoxazole and trimethoprim. Sulfamethoxazole could be
 effective in the treatment of tuberculosis as shown by Forgacs et al. and Huang et al.

 Furthermore, with dried blood spot (DBS) analysis, the exposure to co-trimoxazole could be
 analyzed with only some blood drops withdrawn with a finger prick on paper. This paper is
 suitable for storage, transportation and subsequently analysis without additional cooling or
 storage requirements.

 Objective:

 The main objective of this prospective clinical trial is to evaluate pharmacokinetics of 960
 mg co-trimoxazole in TB patients. This clinical trial will provide important information on
 PK of co-trimoxazole in TB patients for future studies.

 The second objective is to calculate the T>MIC and AUC0-24h/Minimal inhibitory concentration
 (MIC) ratio as efficacy predicting parameter. Furthermore, the analysis of dried blood spots
 will be clinically validated by comparing results of blood samples withdrawn from venous
 blood versus withdrawn by finger prick and transferred to filter paper. Retrospectively, data
 from this study can be used for limited sampling strategies for co-trimoxazole based on a
 pharmacokinetic population model constructed from the full PK curves of the patients.

 Study design:

 A prospective pharmacokinetic study.

 Study population: 12 TB patients.

 Intervention: on 4 to 6 days, 960 mg co-trimoxazole daily will be added to the normal
 treatment regimen.

 Main study parameters/endpoints:

 The pharmacokinetic parameters (Vd, Cl, AUC, etc) of co-trimoxazole are the primary endpoints
 of the study. The T>MIC and AUC0-24h/Minimal inhibitory concentration (MIC) ratio are most
 likely the best predictive parameters for efficacy of co-trimoxazole treatment and will be
 calculated for a range of M tuberculosis isolates.
Inclusion Criteria:

 -  TB Patients with normal susceptible Mycobacterium tuberculosis

 -  Patients older than 17 and younger than 64 years.

 Exclusion Criteria:

 -  Pregnancy or breast feeding

 -  Patients with hypersensitivity to sulfonamide or trimethoprim

 -  Concomitant treatment with vitamin K antagonists (acenocoumarol)

 -  Patients with preexisting renal dysfunction or concomitant treatment of angiotensin
 converting enzyme inhibitors and potassium -sparing diuretics) that may exacerbate the
 hyperkalemic effect of SXT.

 -  Patients treated with methotrexate, phenytoin, sulfonylureas (glibenclamide,
 gliclazide, glimepiride en tolbutamide) or procainamide hydrochloride.

 -  Patients that have gastrointestinal complaints like diarrhea and vomiting (observed)

 -  Patients that have experienced an adverse effect to SXT or similar antibiotic drugs.

 -  Patients with HIV or AIDS.