Summary.-Antibodies to bleomycin were raised by immunization of sheep and rabbits with bleomycin-albumin conjugates. The combination of a high-titre, highavidity sheep antiserum and iodinated bleomycin produced a radioimmunoassay sensitive to 8 ng of bleomycin per ml of plasma or urine. Untreated specimens (100 tul) of plasma or urine could be added directly to the assay tubes. The antiserum was specific for bleomycin and showed no cross-reaction with other anticancer agents used in combination chemotherapy. Over a concentration range of 20-100 ng/ml, recovery of bleomycin from plasma was 110% and from urine, 93%. Repeated assay of plasma samples showed a decrease in bleomycin levels unless the samples were kept at 4°C or below. Assay of bleomycin levels in plasma and urine from patients under treatment with bleomycin showed similarities with results reported using a microbiological assay. The radioimmunoassay offers a more reliable, rapid and sensitive method for the measurement of bleomycin. BLEOMYCIN (BM) is a group of antineoplastic antibiotics, produced by the fungus Streptomyces verticillus, the members of which are partially polypeptide in structure (Umezawa, 1973). Although there are many reported components of varying activity (Cohen and I, 1976), the therapeutic preparation consists mainly of bleomycin A2 and B2. These have proved particularly useful in the treatment of squamous-cell carcinoma, sarcoma and malignant lymphoma. The minimal suppressive effect of BM on human bone marrow is an important attribute, but the appearance of pulmonary toxicity is a side effect which is unpredictable at low dose and increases rapidly with high doses. Continuous monitoring of the blood levels of BM during therapy may, therefore, be of benefit in restricting toxic side effects whilst maintaining maximal antineoplastic activity.The principal method for BM measurement has been assessment of the inhibition of bacterial growth on culture medium by the samples under analysis (Ohnuma et al., 1974). Whilst this technique possesses sufficient sensitivity for the estimation of blood and urine BM levels, the procedure is much more time-consuming than radioimmunoassay (RIA).The comparatively high molecular weight of BM and its peptide-like structure confer the property of immunogenicity on protein conjugates of the drug, which permits rapid production of anti-BM sera. In addition, the drug is susceptible to simple iodination. With these reagents a rapid RIA procedure can be developed (Broughton and Strong, 1976). MATERIALS AND METHODSPreparation of immunogen.-Bleomycin sulphate (donated bv Lundbeck Ltd.) was conjugated to bovine serum albumin (BSA) by a carbodiimide condensation reaction. 90 mg of BM (Lot UIIAS) and 100 mg of BSA were dissolved in 5 ml of distilled water. 70 mg of ethyl-(dimethyl-amino-propyl)-carbodiimide was then added, and the solution stirred overnight at room temperature. Unconjugated BM was removed by dialysis against several changes of 500-ml volumes of distilled water. The conjugate solution was

A radioimmunoassay has been developed for propranolol with a sensitivity of 2.37 nmol l-1 in unextracted plasma using a 50 microliter sample. Plasma concentration measurements were made on samples from volunteers for up to 8 h after they had been given 5, 10, or 40 mg of propranolol by mouth. Analysis of the results showed that mean elimination half-lives and total body clearances were similar following each of the doses and that the area under the curve was proportional to the dose. Steady-state propranolol concentrations in 17 patients on regular propranolol treatment were linearly related to the dose ver the range 20-640 mg d-1; the regression line extrapolated to the origin. These data indicate non-saturable kinetics for the hepatic metabolism of propranolol within the dose ranges investigated and lead us to believe that there is no 'oral-threshold' dose for propranolol. The radioimmunoassay may be useful in clinical practice for monitoring plasma propranolol concentrations and for detecting patient compliance.

1 The cytotoxic agent, vinblastine, was conjugated to albumin, using the Mannich reaction. Rabbits immunized with two conjugates, containing differing amounts of hapten, produce antibodies which bound [3H]‐ vinblastine. 2 Antisera from one rabbit cross‐reacted with both vinblastine and vincristine and were used to develop radioimmunoassays for measuring their concentration in plasma. 3 The antisera showed no cross‐reactivity with other alkaloids or cytotoxic drugs and provided assays sensitive to a concentration of 2.1 ng vinblastine or 3.8 ng vincristine/ml of plasma added direct to the assay tubes. 4 This is sufficiently sensitive to permit the measurement of plasma vinblastine levels for up to 24 h after the intravenous administration of 15 mg of the drug.

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SUMMARY The bioequivalence of two different tablets and a solution, each containing 10 mg propranolol hydrochloride was studied in twelve healthy volunteers. Single oral doses of each preparation were administered at intervals of one week. Samples of blood for propranolol radioimmunoassay were taken up to 8 h after dosing. The plasma propranolol concentration at 0.5 h was significantly higher for the solution than for the two tablet formulations which did not differ significantly from each other at any sampling point. The area under the curve was similar for all three preparations. The study demonstrated that the three different preparations of propranolol were bioequivalent.