May 27, 2017
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Mechanism of Action

Clonidine stimulates alpha-adrenoceptors in the brain stem. This action results in reduced sympathetic outflow from the central nervous system and decreases in peripheral resistance, renal vascular resistance, heart rate, and blood pressure.


With immediate-release clonidine, blood pressure declines within 30 to 60 minutes after an oral dose, the maximum decrease occurring within 2 to 4 hours. Renal blood flow and glomerular filtration rate remain essentially unchanged. Normal postural reflexes are intact; therefore, orthostatic symptoms are mild and infrequent. These studies also show a reduction (15% to 20%) of cardiac output in the supine position with no change in the peripheral resistance. At a 45° tilt, there is a smaller reduction in cardiac output and a decrease of peripheral resistance. During long-term therapy, cardiac output tends to return to control values, while peripheral resistance remains decreased. Slowing of the pulse rate has been observed in most patients given clonidine, but the drug does not alter normal hemodynamic response to exercise.

Tolerance to the antihypertensive effect of clonidine may develop in some patients.

Other studies in patients taking immediate-release clonidine have provided evidence of a reduction in plasma renin activity and in the excretion of aldosterone and catecholamines. The exact relationship of these pharmacologic actions to the antihypertensive effect of clonidine has not been fully elucidated.

Clonidine acutely stimulates growth hormone release in both children and adults, but does not produce a chronic elevation of growth hormone with long-term use.


Following oral administration of Jenloga (clonidine tablets) , peak clonidine levels are reached in 4 to 7 hours, and the plasma half-life averages 13 hours. The absorption of clonidine from Jenloga (clonidine tablets) is not affected by food. Following oral administration of the immediate-release formulation, about 40-60% of the absorbed dose is recovered in the urine as unchanged drug in 24 hours and about 50% of the absorbed dose is metabolized in the liver.

The half-life of clonidine from the immediate-release formulation increases up to 41 hours in patients with severe impairment of renal function. Although studies of the effect of renal impairment and studies of clonidine excretion have not been performed with Jenloga (clonidine tablets) , results are likely to be similar to those of the immediate-release formulation.

The peak to trough ratio (Cmax/Cmin) of clonidine, following repeat dosing with Jenloga (clonidine tablets) , ranges from 1.4 to 1.5. The plasma concentrations of clonidine increased proportionately with increase in dose over 0.1 mg - 0.6 mg twice daily.

Clinical Studies

Jenloga (clonidine tablets) was studied in a single-dose pharmacokinetic study in healthy subjects [see CLINICAL PHARMACOLOGY] and in a one-month pharmacokinetic/pharmacodynamic (PK/PD) study in patients with mild to moderate hypertension.

In the PK/PD study, 12-15 mild-moderate hypertensive patients per treatment group were randomized to Jenloga (clonidine tablets) 0.2, 0.4 or 0.6 mg per day in two equal doses (morning and evening). Ambulatory measurements of blood pressure and heart rate were done at baseline and on day 26 of dosing. The changes from baseline in ambulatory measurements of blood pressure and heart rate for the different doses at day 26 are shown below.

Figure 1: Change from baseline in hourly Systolic blood pressure in mnHg.

Change from baseline in hourly Systolic blood pressure in mnHg -  Illustration

Figure 2: Change from baseline in hourly diastolic blood pressure in mnHg.

Change from baseline in hourly diastolic blood pressure in mnHg -  Illustration

Figure 3: Change from baseline in hourly average heart rate in beats per minute.

Change from baseline in hourly average heart rate in beats per minute - Illustration

Last reviewed on RxList: 11/9/2016
This monograph has been modified to include the generic and brand name in many instances.

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