Nifedipine (NIF) is a new calcium antagonist, which is already widely used as an antianginal and antihypertensive drug. In general NIF is well tolerated (Terry 1982), but in this study surprisingly high incidence of nausea and vomiting after ingestion of NIF was observed.
Ten healthy volunteers (age 21–24 y) participated in a pharmacokinetic cross-over study on two slow-release NIF tablets and two liquid-filled NIF capsules. After 8 h of fasting, 20 mg of NIF was given orally; eating was allowed 4 h later. Each volunteer stated the side effects and their duration and intensity. Before the study volunteers were informed about the possibility of headache, flushing of the skin and dizziness.
All the volunteers experienced side effects. The most common (9/10) and the most intense untoward effect of NIF was headache, which was at its worst 4–8 h after ingestion of drugs. One volunteer withdrew because of unbearable nausea, vomiting and weakness; also the others felt nauseous (6/9), and 4 of them vomited. These symptoms did not begin until 5 h after the administration of the drugs, and after the first meal, which is very late compared to the rapid absorption (Tmax 1–2 h) and elimination (T1/2 1–3 h) of the active principle (Foster et al. 1983). In 22 previous pharmacokinetic studies (Saano et al. 1983; unpublished) on various drugs (not antiemetic), no such adverse reactions occurred, although the test arrangements (volunteer age, blood sampling, fasting, standard meals) were similar.
Slow-release NIF tablets caused dizziness significantly less frequently (p < 0.01; Wilcoxon’s signed rank test for paired samples) than capsules. Other side effects were equally intense and equally frequent after both preparation forms.
The results suggest that gastrointestinal side effects of NIF may be more common and more intense than expected. These untoward effects may be of importance especially when NIF is used as an antihypertensive, where patients are younger and more active than NIF-treated patients suffering from angina pectoris.