Pharmacokinetics and pharmacodynamics of long-acting propranolol 60-mg capsules: a comparative evaluation.

This double-blind, placebo-controlled, four-period cross-over study was undertaken to evaluate the sustained-release characteristics of long-acting propranolol hydrochloride (Inderal LA, Ayerst Laboratories, New York, NY) 60 mg qd, to compare the pharmacokinetic and pharmacodynamic properties of this formulation with conventional propranolol 20 mg tid, and to evaluate the proportionality of long-acting propranolol 60 mg (LA 60 mg) and long-acting propranolol 80 mg (LA 80 mg). Pharmacodynamic effects were evaluated in 34 healthy subjects by assessing heart rate, systolic blood pressure, and the product of heart rate and systolic blood pressure (double product) after exercise-induced tachycardia following both acute (day 1) and steady state (day 4) drug administration. The Cmax following administration of LA 60 mg was 9.5 and 11.4 ng/mL on days 1 and 4, respectively, compared with 18.8 and 20.0 ng/mL with 20 mg tid (P less than .0001). The tmax for LA 60 mg was significantly later (P less than .0001) than for conventional propranolol. Additionally, the apparent plasma half-life was significantly longer (P less than .0001) than with conventional propranolol. The LA 60-mg formulation was dose proportional to the LA 80-mg formulation. Pharmacodynamic evaluations showed no significant differences between LA 60 mg and 20 mg tid at any times tested with either acute or steady state dosing. This study demonstrates that LA 60 mg displays characteristics of a sustained-release formulation, is proportional with LA 80 mg, and produces pharmacodynamic effects that are similar to 20-mg tid dosing.

Initial rate kinetics and evidence for duality of mediated transport of adenosine, related purine nucleosides, and nucleoside analogues in L1210 cells.

In studies using a rapid kinetic technique, evidence was derived for multiplicity of systems mediating [3H]adenosine transport in L1210 cells. A variety of approaches were used in discriminating between transport and kinase-mediated phosphorylation. Under these conditions, two systems mediating influx were delineated which exhibited high-affinity [Km = 13.9 +/- 2 (S.E.) microM] or low-affinity [Km = 199 +/- 27 microM] for [3H]-adenosine. Both systems exhibited high capacities, but that associated with the low-affinity system (V 37 degrees max = 263 +/- 43 nmol = 99.6 +/- 12 nmol sec/g, dry weight). The relative difference in affinity of these two systems during influx was also reflected in the values for influx Ki obtained with other nucleosides and nucleoside analogues. Influx of [3H]-adenosine by each mediated system was inhibited by 6-(2-hydroxy-5-nitrobenzyl)thioguanosine, a specific transport inhibitor, and by 9-beta-D-arabinofuranosylpurine-6(1H)thione which is not phosphorylated in L1210 cells. Influx kinetics were the same in L1210 cells, in adenosine triphosphate-depleted L1210 cells (L1210/ara-C/MMPR) which have substantially reduced ability for [3H]adenosine phosphorylation, and in the presence of 2'-deoxycoformycin, a potent inhibitor of adenosine deaminase. The same multiplicity in mediated influx of [3H]adenosine was shown at 0 degrees when transport became rate limiting to total uptake. The high-affinity system mediating [3H]adenosine influx was also elucidated in L1210 cell plasma membrane vesicles in the presence or absence of 2'-deoxycoformycin. Almost all of the natural nucleosides examined competed less effectively with [3H]adenosine for influx by the high-affinity system than by the low-affinity system. These results are discussed with respect to possible pharmacological implications.

Schedule-dependent synergism of methotrexate and vincristine against murine L1210 leukemia.

BD2F1 mice were inoculated with 10(6) L1210 murine lymphocytic leukemia cells and treated simultaneously with methotrexate and vincristine or with methotrexate followed by vincristine greater than or equal to 24 hours later. Four to six doses of methotrexate, 48 mg/kg ip, administered every 4 days beginning on Day 1 resulted in a 168%-228% increase in lifespan, while vincristine, at 0.5 mg/kg ip, given on the same schedule until death (two or three doses) gave only a 37% increase in lifespan. Simultaneous administration of both agents resulted in a therapeutic effect which was approximately additive. When vincristine was given 24 hours or 24 and 72 hours after the methotrexate, a further increase (70%-100%) in lifespan over that expected from an additive effect and long-term survivors (greater than 90 days) were obtained. Synergism between the two agents and long-term survivors were also seen with higher methotrexate concentrations (72 or 96 mg/kg) given in four or five courses. If therapy was initiated on Day 2 when the peritoneal tumor burden was approximately 2 x 10(7) cells, the combination of methotrexate with delayed vincristine still resulted in an increased therapeutic effect over that obtained with either drug alone, or that expected on an additive basis.

Antitumor properties of a new folate analog, 10-deaza-aminopterin, in mice.

A new folate analog, 10-deaza-aminopterin, was substantially more active than methotrexate, following sc administration in mice, against three of five ascites tumors and two of three solid tumors. For ascites tumors, maximum increases in lifespan (using 6--12 mg/kg q2d X 5) with 10-deaza-aminopterin versus methotrexate were + 171.2%/+ 149.8% against L1210 leukemia, +118.4%/+109.1% against P815 plasmacytoma, +64%/+20.9% against Ehrlich ascites carcinoma, +84.2%/+44.8% against Taper liver tumor, and greater than +159.6%/+64.0% against Sarcoma 180 with longterm survivors after 10-deaza-aminopterin. In a smaller number of experiments comparing LD10 dosages (given q2d X 5) of aminopterin, methotrexate, and 10-deaza-aminopterin, aminopterin was the least effective and 10-deaza-aminopterin was the most effective against the L1210 leukemia, Sarcoma 180, and Ehrlich ascites tumors. Following oral administration (3--6 mg/kg q2d X 5), a twofold greater increase in survival time was obtained against the L1210 leukemia with 10-deazaaminopterin (+122.8%) versus methotrexate (+57%). At a dosage of 6 mg/kg q1d X 5 against solid tumors, the relative tumor volumes (treated/control X 100%) were 12%/41% for Sarcoma 180, 16%/31% for Taper liver tumor, and 20%/30% for Ehrlich ascites carcinoma. Overall, the data suggest a broader spectrum of effective antitumor action in mice and a potential for the expanded clinical utility of this category of agent.

Optimization of high-dose methotrexate with leucovorin rescue therapy in the L1210 leukemia and sarcoma 180 murine tumor models.

An analysis of dose and schedule dependence of calcium leucovorin rescue during high-dose methotrexate therapy of ascitic forms of l1210 leukemia and Sarcoma 180 is reported. Schedules with very delayed "low-dose" leucovorin rescue following lethal doses of methotrexate were highly effective in preventing toxicity and achieved a pronounced antitumor effect in both ascites tumor models. Best results were obtained on a schedule of methotrexate (400 mg/kg s.c.) followed 16 to 20 hr later by calcium leucovorin (12 mg/kg s.c.) given once every 2 hr for a total of 5 doses. Progressive increases in the calcium leucovorin dosage on any schedule reduced both toxicity and the antitumor effect of methotrexate in each model. Following a single course of therapy, essentially no toxicity was observed, and the antitumor effects were 2-fold (L1210 leukemia) and 4-fold (Sarcoma 180) greater than a single, maximally tolerated dose (24/kg s.c.) methotrexate alone. An increase in the methotrexate dosage to 800 mg/kg s.c. with or without an increase in calcium leucovorin dosages on the same schedule did not appreciably increase the antitumor effect observed. Two courses of high-dose methotrexate (400 mg/kg s.c.) with leucovorin rescue (24 mg/kg s.c. 16, 20, and 24 hr after drug) given with an 8-day interval between courses doubled the total antitumor effect in each model with no substantial increase in toxicity and gave long-term survivors with Sarcoma 180. The results, overall, are in close agreement with prior prediction for schedule and dose dependence made on the basis of related pharmacokinetic and biochemical studies in murine tumor models reported from this laboratory.

Experimental chemotherapy with 5-arylpyrimidine antifolates: Further studies on toxicity and the responsiveness of ascitic, solid, and intracranial sarcoma 180 to DDMP and DDMP with citrovorum factor.

Multiple-dose toxicity of the 5-arylpyrimidine DDMP showed marked seasonal variation and sex dependence in BD2F1 mice. Considerable therapeutic activity against the ascitic, solid, and intracranial forms of Sarcoma 180 was demonstrated. Antitumor effects were highly schedule and dose dependent at a limited number of doses between 16 and 40 mg/kg. Antitumor activity (increase in lifespan) was approximately twofold greater against the ascitic tumor compared to the intracranial tumor at each dose level. The use of citrovorum factor rescue appeared to improve the therapeutic index of DDMP against intracranial Sarcoma 180 on specific multiple-dose schedules. Citrovorum factor rescue did not result in a greater initial antitumor effect of DDMP against the solid Sarcoma 180, but the effect was maintained for a longer period of time by allowing an increase in the number of doses which could be administered without toxicity.

Biochemical and pharmacokinetic effects of leucovorin after high-dose methotrexate in a murine leukemia model.

The administration of calcium leucovorin, either concurrently or after high dosages of methotrexate in L1210 leukemic mice, has both pharmacokinetic and biochemical effects in tumor cells and drug-limiting proliferative normal tissue in small intestine. A reduction in the maximal level of accumulation and retention of exchangeable drug (unbound to dihydrofolate reductase) in tissue could be demonstrated when calcium leucovorin was given simultaneously with methotrexate at equal or greater dosages than the latter. The dose dependence for calcium leucovorin-introduced drug loss is similar in both tissues and showed the expected variation when the time interval between methotrexate and calcium leucovorin doses was increased. With 400 mg methotrexate per kg, greater than 96 mg calcium leucovorin per kg were required maximally to affect overall drug retention in tissue 2 hr after drug, whereas only 24 mg calcium leucovorin per kg were required 16 hr after drug. Calcium leucovorin, given after methotrexate, induced synchronous recovery of DNA synthesis (measured by labeled deoxyruridine incorporation) in both small intestine and L1210 cells. An initial cycle of synthesis was induced in the presence of exchangeable levels of drug. Two hr after methotrexate, 12 mg/kg, calcium leucovorin induced an immediate but only partial (20 to 25% of control rate) recovery of synthesis with dose dependence from 3 to 12 mg calcium leucovorin per kg. Less synthesis was induced after 96 mg/kg and almost none after methotrexate, 400 mg/kg. With calcium leucovorin, 24 mg/kg, given 2 hr after methotrexate, 12 or 96 mg/kg, a major cycle of synthesis occurred when total drug levels approached the equivalence of the dihydrofolate reductase content. The magnitude of this cycle of synthesis in both L1210 cells and small intestine was the same as that seen in animals recovering from methotrexate alone. However, this is based on the assumption that an approximately equivalent relationship between DNA synthesis and labeled doexyuridine incorporation in each tissue during the period of maximal incorporation within the cycle. The major effect of calcium leucovorin, then, was to induce an earlier resumption of DNA synthesis as a consequence of the pharmacokinetic effect in each tissue. With calcium leucovorin, 24 or 400 mg/kg, given 16 hr after methotrexate, an identical effect on drug retention was observed in both L1210 cells and small intestine. Although there was a difference in the time course for recovery in small intestine at each dosage of calcium leucovorin, the recovery of DNA synthesis as drug levels approached the dihydrofolate reductase content was similar in magnitude. In L1210 cells, however, substantial recovery of synthesis to a comparable level and with a similar time-course occurred only after leucovorin, 400 mg/kg. Little or no recovery of DNA synthesis was observed after calcium leucovorin, 24 mg/kg, during the same time period. This dosage schedule (methotrexate, 400 mg/kg, s.c...

Tissue pharmacokinetics, inhibition of DNA synthesis and tumor cell kill after high-dose methotrexate in murine tumor models.

In Sarcoma 180 and L1210 ascites tumor models, the initial rate of methotrexate accumulation in tumor cells in the peritoneal cavity and in small intestine (intracellularly) after s.c. doses up to 800 mg/kg, showed saturation kinetics. These results and the fact that initial uptake in these tissues within this dosage range was inhibited to the expected relative extent by the simultaneous administration of leucovorin suggest that carrier mediation and not passive diffusion is the major route of drug entry at these extremely high doses. Maximum accumulation of intracellular drug occurred within 2 hr and reached much higher levels in small intestine than in tumor cells at the higher dosages. At a 3-mg/kg dose of methotrexate s.c., intracellular exchangeable drug levels persisted more than four times longer in L1210 cells than in small intestine, but differences in persistence (L1210 cell versus gut) diminished markedly with increasing dosage. At 96 mg/kg, the difference in persistence was less than 2-fold. In small intestine and L1210 cells, theduration of inhibition of DNA synthesis at different dosages correlated with the extent to which exchangeable drug was retained. Toxic deaths occurred when inhibition in small intestine lasted longer than 25 to 30 hr. Recovery of synthesis in small intestine and L1210 cells occurred synchronously and only below dosages of 400 mg/kg. Within 24 hr after dosages of greater than 24 mg/kg, the rate of tumor cell loss increased to a point characterized by a single exponential (t1/2=8.5 hr). The total cell loss, but not the rate of cell loss, was dose dependent.

Experimental chemotherapy with 5-arylpyrimidine antifolates: preliminary studies on toxicity and responsiveness of sarcoma 180 to DDMP (NSC-19494) and DDMP with citrovorum factor (NSC-3590).

The 5-arylpyrimidine antifolate DDMP showed appreciable therapeutic activity against an ascitic form of Sarcoma 180 in BD2F1 mice. Antitumor effects were highly schedule and dose dependent at a limited number of doses within the range of 8--40 mg/kg. The best results (increased lifespan = 112%) were obtained with two doses of DDMP at 40 mg/kg given 4 days apart. The incorporation of citrovorum factor rescue in dose schedules with DDMP appeared to improve the therapeutic index. In multiple-dose schedules with citrovorum factor allowing an average of eight doses of DDMP at a maximum level of 16 mg/kg, increases in median lifespan were greater than 158% with a number of long-term survivors.