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Biomedical subjects

G Rivera

Publications and source records attributed to G Rivera.

83 records · Page 5Linked to original sources
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A model for dosing gentamicin in children and adolescents that adjusts for tissue accumulation with continuous dosing.

The pharmacokinetics of gentamicin were evaluated in 50 children and adolescents during a multiple dose course of therapy. Parameters of a 2-compartment pharmacokinetic model were derived from serial serum concentrations and urinary excretion rates measured for up to 11 days following the last dose of gentamicin administered to 10 of these patients. These parameters were used to simulate changes in serum concentrations and half-lives that would occur during a standard 6-hour dosing interval with continuous dosing. The data indicated that the half-life for decline in serum concentrations after the first dose was 76 +/- 8% of the half-life at steady-state, and that the half-life after the fourth dose exceeded 90% of the steady-state half-life. These underestimations of the steady-state serum half-life were incorporated into a 1-compartment model to simulate steady-state peak and nadir serum concentrations by using pharmacokinetic parameters measured after the first dose of gentamicin administered to 40 patients. Steady-state serum concentrations predicted by the true 1-compartment model and by the adjusted model were compared with concentrations measured at steady-state. The concentrations predicted by the former model were significantly different from and consistently less than measured concentrations. Concentrations predicted by the adjusted model were not significantly different from concentrations measured at steady-state. These data indicate that the new model offers a simple and more accurate method of simulating steady-state concentrations from pharmacokinetil for individualising therapy.

Adolescent↗
PubMedDate not supplied

4'-demethylepipodophyllotoxin 9-(4,6-o-2-thenylidene-beta-D-glucopyranoside) (NSC-122819; VM-26) and 4'-demethylepipodophyllotoxin 9-(4.6-0-ethylidene-beta-D-glucopyranoside) (NSC-141540; VP-16-213) in childhood cancer: preliminary observations.

We evaluated the responses of 39 children with cancer who, after failure to respond to conventional chemotherapeutic agents, received either or both of two epipodophyllotoxins: 4'-demethylepipodophyllotoxin 9-(4,6-o-2-thenylidene-beta-D-glucopyranoside) (NSC-122819) and 4'-demethylepipodophyllotoxin 9-(4,6-o-ethylidene-beta-D-glucopyranoside) (NSC-141540). Seventeen patients has acute lymphocytic leukemia (ALL). 12 had acute nonlymphocytic leukemia (ANLL), and ten had solid tumors. Initially, the patients in each disease category were randomized to receive 50 mg/m2/dose of NSC-122819 intravenously (iv) twice weekly or 75 mg/m2/dose iv of NSC-141540 twice weekly for 4 weeks. Drug dosages and schedules of administration were adjusted during the course of the study. Although objective responses were not detected in the heterogeneous group of solid tumor patients, definite clinical responses were obtained in nine of the 29 patients with acute leukemia. The responses to the two epipodophyllotoxins were noted in patients with ALL as well as in patients with ANLL. Toxic side-effects included nausea, vomiting, diarrhea, fever, alopecia, leukopenia, and thrombocytopenia. These results, the first reported with both NSC-122819 and NSC-141540 in childhood cancer, indicate that the epipodophyllotoxins are well tolerated and may be effective against acute leukemia.

Acute Disease↗
PubMedDate not supplied

Effective remission induction of refractory childhood acute nonlymphocytic leukemia by VP-16-213 plus azacitidine.

Thirty-eight children and young adults with advanced acute nonlymphocytic leukemia (ANLL) in relapse were treated with VP-16-213 plus azacitidine (5AZ). Each patient had previously received many chemotherapeutic drugs, including anthracyclines and cytarabine. Initially, 16 patients received a 5-day course of VP-16-213 (100 mg/m(2)) daily x 3 days and 5AZ 9150 mg/m(2)) daily x 2 days, repeated after 9-16 days. Since this treatment produced marrow hypoplasia and complete remission (CR) in only one of 16 patients, a more intensive regimen was devised: the remaining 22 patients received a course of VP-16-213 (200 mg/m(2)) daily x 3 days, followed by 5AZ (300 mg/Fm(2)) daily x 2 days, repeated after 1-2 days until the bone marrow became hypoplastic. After two to four courses, 18 patients had marrow hypoplasia and ten of these achieved CR. The proportion of patients achieving CR with the higher doses was significantly greater than that with the initial doses )P less than or equal to 0.05). The toxicity also increased with the higher doses, with major problems due to prolonged pancytopenia. Supportive therapy was required for severe bleeding and infections. We conclude that the intensive treatment with VP-16-213 plus 5AZ can effectively induce remission in patients with refractory advanced acute nonlymphocytic leukemia.

Acute Disease↗
PubMedDate not supplied

Femoral-femoral bypass. Non-invasive hemodynamic evaluation.

Seven patients who underwent femoral-femoral by pass between June 1980 and September 1982 underwent pre-operative angiography and pre and post-operative non-invasive evaluation to determine: (1) the hemodynamic effects created by the crossover graft, and (2) if angiographic findings would be predicative of post-operative results. The mean ankle/arm (a/a) index in the donor extremity changed from 0.82 +/- 0.20 to 0.70 +/- 0.27 (NS). The a/a index in the recipient extremity increased from 0.39 +/- 0.30 to 0.74 +/- (p less than 0.02). One patient developed a "steal" syndrome. There was no correlation between angiographic findings and post-operative changes. This study demonstrated a significant increase in recipient extremity ankle pressure and a clinically insignificant decrease in donor limb pressure.

Aged↗