These data are from a randomized double blind trial on three treatments
for hypertension. The treatments are 25-50 mg Carvedilol (A), 20-40 mg 
slow-release Nifedipine (B), and 50-100 mg Atenolol (C). 29 clinical 
centers participated and screened 311 participants, of whom 293 were 
eligible to participate and randomized into the trial. Two pre-treatment 
and four post-treatment visits were made to the clinics. 255 participants
completed the study.

Eligibility criteria were: systolic blood pressure (SBP) 160-220 mm Hg and 
diastolic blood pressure (DBP) 95-115 mm Hg if medication was not being taken
at the time of assessment, or SBP 140-200 mm Hg and DBP 90-105 mm Hg if
medication was being taken at the time of assessment. Participants also 
must have had a history of hypertension for at least 6 months and be between
18 and 70 years old.

Exclusion criteria were: asthma, congestive heart failure, heart block,
clinically significant renal or hepatic impairment, diabetes requiring
therapy, and mycardial infarction within the previou 6 months.

Visit 1: eligibility screening. Diastolic blood pressure, cardiac 
function (heart rate and ECG), and occurrence of cold feet (1=none,
2=occasionally, 3=on most days, 4=most of the time, and 5=all of the
time) were measured. Those who were eligible 
were given a placebo to take for one week, after which they were asked 
to return for a second visit.

Visit 2: randomization. Those who were still eligible were then randomized 
to one of the three treatments. Heart rate and blood pressure were
measured 1 hour after the first dosing of the randomized treatment.

Visits 3-5: DBP and occurrence of cold feet were measured once every two 
weeks for three visits.

Visit 6: DBP and occurrence of cold feet were measured six weeks after visit 5.

Measurements on cardiac function, laboratory values, and adverse events
were also recorded at each post-treatment visit. The data set contains 
data for 288 of the 293 randomized participants (it is unknown why
the other 5 are not included).

These data were reported on in Hall, Prescott, Hallman, Dixon, Harvey,
and Ball (1991). "A comparative study of Carvedilol, slow release
Nifedipine, and Atenolol in the management of essential hypertension,"
Journal of Cardiovascular Pharmacology, 18(4 SUPPL): S35-S38.

Data source: Brown H and Prescott R (1999). Applied mixed models in 
medicine. Chichester, England: John Wiley & Sons, Inc.