Degradation of carmustine in mixed solvent and nonaqueous media

Voltammetric and amperometric determination of N-nitroso antineoplastic drugs at mercury and amalgam electrodes

A hanging mercury drop electrode and a mercury meniscus modified silver solid amalgam electrode were used as electroanalytical sensors for voltammetric determination of antineoplastic drugs carmustine, lomustine and streptozotocin containing reducible N-nitroso groups. On the example of carmustine it was shown that its one-step reduction proceeds at substantially more negative potentials at amalgam electrode as compared with mercury electrode. Both electrodes offer satisfactory repeatability of current response (relative standard deviations < 5%) using DC voltammetry and differential pulse voltammetry. The achieved limits of determination lie mostly in the 10–7 mol l–1 concentration range. The mentioned voltammetric methods were applied to determination of carmustine and lomustine in pharmaceutical formulations. Further, the mercury meniscus modified silver solid amalgam electrode was employed in a “wall-jet” amperometric detection cell in the determination of carmustine by flow injection analysis. Under optimized conditions (run electrolyte Britton– Robinson buffer of pH 7.0; flow rate 5.5 ml min–1; detection potential –1.5 V; injection volume 0.02 ml) the limit of quantitation 7.1 × 10–6 mol l–1 was achieved.

BCNU stability as a function of ethanol concentration and temperature

BCNU is increasingly used in low ethanol (ETOH) concentrations, 5% dextrose-water (D5W), or normal saline (NS) solutions, especially for intra-arterial and prolonged (e.g., 3 day) intravenous (IV) infusions. Little work, however, has been done to evaluate BCNU decomposition rates in concentrations, diluents, and temperatures similar to those employed clinically. This study examined BCNU solutions in ETOH, NS, and D5W to evaluate, conclusively, initial recovery and decomposition rates in these three diluents. Initial BCNU recovery rates were: 95.6 +/- 0.3% (100% D5W), 89.6 +/- 0.5% (15% ETOH), and 85.2 +/- 0.5% (NS) (P less than 0.001). Study of all solutions revealed no measurable BCNU decomposition over 24 hrs (0 degrees C) and no significant difference in decomposition rates between any of the diluents (19.5 degrees C). At 37 degrees C, the solutions showed different half-lives: 14.3 +/- 0.19 hrs (15% ETOH), 10.6 +/- 0.02 hrs (10% ETOH), 8.2 +/- 0.21 hrs (5% ETOH), 7.3 +/- 0.06 hrs (NS), and 6.8 +/- 0.07 hrs (D5W) (P less than 0.001). Decomposition rates between all three temperatures (19.5 degrees C, 37 degrees C, and 50 degrees C) were significantly different (P less than 0.01) for each diluent. Dissolving BCNU powder into either D5W or NS required only 5 min when hand-shaken at body temperature. This study of initial recovery and decomposition rates suggests that, although BCNU decomposition rates were significantly increased at body temperature (37 degrees C), it was quite low and essentially unaffected by different diluents at room temperature (i.e., 19.5 degrees C).(ABSTRACT TRUNCATED AT 250 WORDS)

Stability of solutions of antineoplastic agents during preparation and storage for in vitro assays. General considerations, the nitrosoureas and alkylating agents

In vitro drug sensitivity of tumour biopsies is currently being determined using a variety of methods. For these chemosensitivity assays many drugs are required at short notice, and this in turn means that the drugs must generally be stored in solution. There are, however, a number of potential problems associated with dissolving and storing drugs for in vitro use, which include (a) drug adsorption; (b) effects of freezing; (c) drug stability under the normal conditions of dilution and setting up of an in vitro assay; and (d) insolubility of drugs in normal saline (NS) or phosphate-buffered saline (PBS). These problems are considered in general, and some recommendations for use of solutions of drugs in in vitro assays are suggested. The nitrosoureas and alkylating agents are also investigated in greater detail in this respect. The nitrosoureas are found to be very labile in PBS at pH 7, with 5% degradation (t0.95) occurring in 10-50 min at room temperature. These values are increased about 10-fold on refrigeration and about 5- to 10-fold on reduction of the pH of the medium to pH 4-5. At pH 7 and room temperature, t0.95 is observed in under 1 h with the alkylating agents nitrogen mustard, chlorambucil, melphalan, 2,5-diaziridinyl-3,6-bis(2-hydroxyethylamino)-1,4-benzoquinone (BZQ), dibromodulcitol, dibromomannitol, treosulphan, and procarbazine. Of the other alkylating agents, 4-hydroperoxycylophosphamide (sometimes used in vitro in place of cyclophosphamide), busulphan, dianhydrogalactitol, aziridinylbenzoquinone (AZQ), and dacarbazine have a t0.95 of between 2 and 24 h, while ifosfamide and pentamethylmelamine are both stable in aqueous solution for greater than 7 days. About half the drugs studied in detail have been stored frozen in solution for in vitro use, although very little is known about their stability under these conditions.