Source: Health Products Regulatory Authority (IE) Revision Year: 2022 Publisher: Glenwood GmbH, Pharmazeutische Erzeugnisse, Arabellastrasse 17, 81925 Munich, Germany
Clonidine acts primarily on the central nervous system, resulting in reduced sympathetic outflow and a decrease in peripheral resistance, renal vascular resistance, heart rate and blood pressure. Renal blood flow and glomerular filtration rate remain essentially unchanged. Normal postural reflexes are intact and therefore orthostatic symptoms are mild and infrequent. 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 haemodynamic response to exercise.
The efficacy of clonidine in the treatment of hypertension has been investigated in five clinical studies in paediatric patients. The efficiacy data confirms the properties of clonidine in reduction of systolic and diastolic blood pressure. However, due to limited data and methodological insufficiences, no definitive conclusion can be drawn on the use of clonidine for hypertensive children.
The efficacy of clonidine has also been investigated in a few clinical studies with paediatric patients with ADHD, Tourette syndrome and stuttering. The efficacy of clonidine in these conditions has not been demonstrated.
There were also two small paediatric studies in migraine, neither of which demonstrated efficacy. In the paediatric studies the most frequent adverse events were drowsiness, dry mouth, headache, dizziness and insomnia. These adverse events might have serious impact on daily functioning in paediatric patients. Overall, the safety and efficacy of clonidine in children and adolescents have not been established (see section 4.2).
The pharmacokinetics of clonidine is dose-proportional in the range of 100-600 micrograms. Clonidine, the active ingredient of Catapres, is well absorbed and no first pass effect exists. It is rapidly and extensively distributed into tissues and crosses the blood-brain barrier as well as the placental barrier. The plasma protein binding is 30-40%.
The mean plasma half life of clonidine is about 13 hours ranging between 10 and 20 hours. The half-life does not depend on the sex or race of the patient but can be prolonged in patients with severely impaired renal function up to 41 hours.
About 70% of the dose administered is excreted in the urine mainly in the form of the unchanged parent drug (40-60%). The main metabolite p-hydroxy-clonidine is pharmacologically inactive. Approximately 20% of the total amount is excreted in the faeces.
The antihypertensive effect is reached at plasma concentrations between about 0.2 and 1.5ng/ml in patients with normal excretory function. A further rise in the plasma levels will not enhance the antihypertensive effect.
There are no preclinical data of relevance to the prescriber which are additional to that already included in other sections of the SPC.
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