Article ; Online: Exploring low clozapine C/D ratios, inverted clozapine-norclozapine ratios and undetectable concentrations as measures of non-adherence in clozapine patients: A literature review and a case series of 17 patients from 3 studies.
2023
Abstract: ... proposed a: 1) clozapine concentration/dose (C/D) ratio which drops to half or more of what is expected ... Results: The first index of non-adherence is a clozapine C/D ratio which is less than half the ratio ... adherence was modeled in two patients: 1) the clozapine C/D ratio dropped to ≥1/2 of what is expected ...
Abstract | Background: Up to 1/2 of outpatients prescribed clozapine may be partially/fully non-adherent, based on therapeutic drug monitoring (TDM). Three indices for measuring partial/full non-adherence are proposed a: 1) clozapine concentration/dose (C/D) ratio which drops to half or more of what is expected in the patient; 2) clozapine/norclozapine ratio that becomes inverted; and 3) clozapine concentration that becomes non-detectable. Methods: These 3 proposed indices are based on a literature review and 17 cases of possible non-adherence from 3 samples: 1) an inpatient study in a Chinese hospital, 2) an inpatient randomized clinical trial in a United States hospital, and 3) and a Uruguayan outpatient study. Results: The first index of non-adherence is a clozapine C/D ratio which is less than half the ratio corresponding to the patient's specific ancestry group and sex-smoking subgroup. Knowing the minimum therapeutic dose of the patient based on repeated TDM makes it much easier to establish non-adherence. The second index is inverted clozapine/norclozapine ratios in the absence of alternative explanations. The third index is undetectable concentrations. By using half-lives, the chronology of the 3 indices of non-adherence was modeled in two patients: 1) the clozapine C/D ratio dropped to ≥1/2 of what is expected from the patient (around day 2); 2) the clozapine/norclozapine ratio became inverted (around day 3); and 3) the clozapine concentration became undetectable by the laboratory (around days 9-11). Conclusion: Prospective studies should further explore these proposed clozapine indices in average patients, poor metabolizers (3 presented) and ultrarapid metabolizers (2 presented). |
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Language | English |
Publishing date | 2023-07-22 |
Publishing country | Netherlands |
Document type | Journal Article |
ZDB-ID | 639422-x |
ISSN | 1573-2509 ; 0920-9964 |
ISSN (online) | 1573-2509 |
ISSN | 0920-9964 |
DOI | 10.1016/j.schres.2023.07.002 |
Database | MEDical Literature Analysis and Retrieval System OnLINE |
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