Acetylsalicylic acid-induced gastrointestinal bleeding determined by a 51Cr method on a day-to-day basis.

The daily gastrointestinal blood loss caused by plain and microencapsulated acetylsalicylic acid (ASA) tablets was compared. Fourteen healthy, male volunteers participated in a double-blind, cross-over study, lasting 38 days. Before drug administration a median gastrointestinal bleeding of 0.9 ml/24 h was observed. During oral intake of 1.5 g ASA twice a day for 5 days, an increased faecal blood loss was seen in all volunteers. The increase was significant for both plain and microencapsulated ASA (p less than 0.01). Plain ASA tablets, however, caused a greater faecal blood loss than the microencapsulated tablets (p = 0.05), maximum median levels being 6.2 ml/24 h and 3.9 ml/24 h, respectively. An optimal design of radiochromium studies for determination of drug-induced gastrointestinal blood loss is discussed.

Absorption of a non-ionic contrast agent from cerebrospinal fluid to blood.

Intrathecal injection of a non-ionic contrast agent in the lumbar area of rabbits resulted in: (1) a rapid rise in blood iodine level with a maximum after 23-46 min; (2) low concentrations in cisterna magna during the observation period (24 h); and (3) complete or almost complete disappearance of visible contrast medium on the radiographs within 30 min. This indicates that after injection in the lumbar area of the rabbit most of the contrast medium absorption takes place from the lumbar area. Similar injections in cisterna magna showed the following: (1) a slow rise in blood level with a maximum after 150-275 min; (2) little or no disappeared of visible contrast medium on the radiographs within the first hour. This indicates that in the rabbit the absorption from the subarachnoid space of the spine takes place at different rates dependent on the level at which the injection has been made and the area of deposition of contrast medium.