P-8: Effects of different dihydropyridine calcium antagonists on plasma norepinephrine in essential hypertension

The objective of this study is to compare the chronic effects of nifedipine GITS, nitrendipine and lercanidipine on BP, HR and plasma norepinephrine levels in patients with mild to moderate hypertension. After a 4 week placebo period, 60 patients of both sexes were randomly allocated to be administered nifedipine GITS 30 to 60 mg od, nitrendipine 20-40 mg od or lercanidipine 10 to 20 mg od for 24 weeks. For the first 4 weeks the lowest dose of each drug was used, then there was a titration. BP, HR and plasma norepinephrine were evaluated at the end of the placebo period and of the treatment period. Norepinephrine was evaluated at trough and after 6 and 12 hours from drug ingestion. The administration of three drugs reduced clinic BP to the same level after 24 weeks, but HR was increased slightly only with nitrendipine (± 2.2 b/min, p< 0.05). The plasma norepinephrine levels (pg/ml)are shown in the table. Placebo nifedipine GITS nitrendipine lercanidipine Through 266 377** 393** 278 6th hour 241 374** 418** 283 12th hour 271 398** 369** 282 * p < 0.05; **p < 0.01 vs placebo. In conclusion the sustained increase in norepinephrine levels after chronic treatment with nifedipine GITS and nitrendipine suggests that chronic sympathetic activation occours with these 2 drugs. On the opposite the lack of increase with lercanidipine suggests that this drug does not activate the sympathetic system. The reason of these differences is unclear; it could be related to the different pharmacological characteristics of the drugs, lercanidipine being lipophilic.