The majority of chronic hemodialysis patients need a combination of several antihypertensive drugs for adequate BP control. The primary objective of this study is to evaluate whether transdermal clonidine can improve blood pressure control or decrease oral antihypertensive agents type or dosage and the secondary objective is to observe incidence of adverse reactions of transdermal clonidine in chronic hemodialysis patients.

It's a randomised crossover clinical trial. Subjects: chronic hemodialysis patients. All subjects will be randomised to 2 groups. Subjects in first group will receive 4 weeks transdermal clonidine plus regular antihypertensive agents treatments first, 2weeks wash-out then and 4 weeks antihypertensive agents without transdermal clonidine. The other group will receive 4 weeks antihypertensive agents without transdermal clonidine first, 2weeks wash-out then and 4 weeks transdermal clonidine plus regular antihypertensive agents treatments. Ambulatory blood pressure, echocardiography, and biochemistry will be detected.

Inclusion Criteria:

1. signed informed consent;
2. age: 18years to 80 years old；
3. on hemodialysis for more than or equal to 3 months, not less than 3 times and 12 hours hemodialysis per week；
4. cardiac function grade I or grade II(NYHA)；
5. Using 1 or more than 1 oral antihypertensive drugs, pre-dialysis systolic blood pressure over 140mmHg or dialysis blood pressure over 90mmHg, post-dialysis systolic blood pressure over 130mmHg or diastolic blood pressure over 80mmHg

Exclusion Criteria:

1. acute infection within 1 month；
2. acute myocardial infarction/cardiac function grade IV/stroke within 3months；
3. LVEF lower than 50% by echocardiography；
4. Dry weight is not suitable by BCM evaluation, more than plus or minus 1kg；
5. Inter-dialysis weight gain exceeds 5% of dry weight；
6. Post-dialysis systolic blood pressure lower than 120mmHg and diastolic blood pressure lower than 70mmHg；
7. Begin or stop recombinant human erythropoietin treatment within 2 weeks before inclusion or 10 weeks after inclusion;
8. Adjust recombinant human erythropoietin dosage to more than 2times or less than half original dosage within 2 weeks before inclusion or 10 weeks after inclusion；
9. The treatment regimen will be amended within 10 weeks and it is expected that the treatment amendment may affect blood pressure；
10. Pregnancy or lactation or planning a pregnancy in 10 weeks；
11. Expected to withdraw hemodialysis treatment in 10 weeks；
12. Allergic to clonidine or its accessories；
13. Undergoing other clinical studies, and the research interventions have an impact on blood pressure；
14. Other clinical conditions that may affect the results