Tamoxifen dosage

Several authors (90,91) have described a variety of cases, seven in all, of malignancies secondary to therapeutic dosages of tamoxifen given for 6 months to 10 years. 

Fig. 5.7. Left panel-, daily imaging of an exemplificative mouse individual treated with tamoxifen at the daily dose of 0.5 mg/day s.c. Right panel photon emission by abdomen in mice treated daily for 21 days with vehicle (controls) 17-beta estradiol (5.5 gg/kg/day s.c.) tamoxifen al low dosage (5.5 gg/kg/day) or at high dosage (0.5 mg/kg/day). Luciferase expression appears to become more elevated at the end of the treatment with tamoxifen indicating, in this tissue, an unpredicted, potential effect of the treatment during prolonged treatments with the drug.

LC/tandem MS assays for tamoxifen metabolites have been described by numerous investigators and used for research purposes [10-12], Figure 1 shows a typical chromatogram for the analyses of these metabolites from a serum sample. Following chronic administration of a standard 20 mg tamoxifen per day dosage on presumably wild-type subjects, typical serum concentrations at steady state were 150 ( 50)ng/mL for tamoxifen, 180 ( 70)ng/mL for /V-desmethytam, 2.5 ( 1.2)ng/mL for 4-hydroxytam, and 5.0 ( 2.5)ng/mL for endoxifen [10],... 

Although tamoxifen is far less likely to induce ocular toxicity at the normal dosage level of 20 mg daily, retinopathy does occur, although it is usually asymptomatic.With high dosages (e.g., 90 to 120 mg twice daily), toxic effects can be observed within 17 to 27 months, as the total cumulative dose exceeds 90 g. 

Tamoxifen Potentiation possible (247,248) Unknown Adjust dosage... 

The common mode of exposure to tamoxifen is through ingestion. It is available in oral dosage form (10 and 20 mg tablets) and may also be inhaled. Vapors may produce explosive dust clouds. Hazardous products include carbon monoxide, carbon dioxide, and nitrous oxide. 

Adverse reactions to tamoxifen are relatively mild and rarely require discoutiuuatiou of therapy. If adverse reac-tious are severe, it is sometimes possible to control severe adverse reactions by dosage reduction without losing control of the disease. 

Evidence is limited to the above reports, but it appears that a clinically important interaction between tamoxifen and warfarin can occur, which apparently affects some but not all patients. Monitor the effects closely if tamoxifen is added to treatment with warfarin or acenocoumarol and reduce the dosage as necessary. The reports cited here indicate a reduction of between one-half to two-thirds for warfarin. In the US, when tamoxifen is being used for the primary prevention of breast cancer, the manufacturer specifically contraindicates concurrent use with warfarin or other coumarins. ... 

Sensory systems Vision Earlier evidence has suggested that tamoxifen might have adverse effects on visual function. The effects of tamoxifen on visual function have been studied using full-field and focal elec-troretinography in 14 women aged 47-72 years who had taken tamoxifen for 2-37 months, in 10 untreated women of similar age with breast cancer, and in 13 healthy women [25 ]. Low-dosage tamoxifen had no retinotoxic effects mean peak-to-peak amphtudes and implicit time were comparable in the three groups. 

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