Clonidine orthostatic hypotension

Clonidine (Catapres) Potential for orthostatic hypotension and CNS adverse effects. Low... 

Many inhibitors of the amine transporters for norepinephrine, dopamine, and serotonin are used clinically. Although specificity is not absolute, some are highly selective for one of the transporters. Many antidepressants, particularly the older tricyclic antidepressants can inhibit norepinephrine and serotonin reuptake to different degrees. This may lead to orthostatic tachycardia as a side effect. Some antidepressants of this class, particularly imipramine, can induce orthostatic hypotension presumably by their clonidine-like effect or by blocking 04 receptors, but the mechanism remains unclear. 

A 39-year-old quadriplegic man with poorly controlled pain had many features consistent with autonomic dysfunction (for example a C4 spinal lesion, orthostatic hypotension, hypertension). He routinely used trans-dermal clonidine and transdermal glyceryl trinitrate as needed for control of acute hypertensive episodes. The clonidine was discontinued, after which his blood pressure fell (maximum systolic and diastolic pressures by about 50 and 25 mmHg respectively). 

Methyidopa (Aldomet) As for clonidine. Also, synthesized to methyinorepinephrine which acts as a weak sympathomimetic "false neurotransmitter" which decreases sympathetic outflow from the CNS. As for clonidine. Used to treat hypertension in pregnant women. Dry mouth, sedation, slight orthostatic hypotension. Some patients experience impotence, psychic disturbances, nightmares, involuntary movements, or hepatotoxicity. 

The manufacturers of clonidine note that a reduced antihypertensive effect may occur with antipsychotics with alpha-blocking properties (e.g. ehlorpromazine), as well as mentioning the risk of orthostatic hypotension.Consider also Clonidine + Tricyclic and related antidepressants% p.884. Although antagonism of the antihypertensive effect of clonidine has been seen in animals given ehlorpromazine, there appear to be no clinical reports. 

Significant sedation can occur with clonidine. While direct respiratory depression is not common, sedation can result in hypopnea and subsequent hypoxemia. Another limiting factor in its use has been the hemodynamic profile that includes initial hypertension followed by hypotension and bradycardia. Orthostatic hypotension in particular can limit its use in both the acute and chronic settings. 

An advantage of clonidine is the absence of orthostatic hypotension, but like a-methyldopa and reserpine it may cause drowsiness, and marked sedation occurs in up to 50% of patients treated in some series. Sedation can be so severe as to proceed to semi-consciousness. Nightmares and delusions are another expression of the drug s influence upon the central nervous system. Apart from sedation, the complaint of dry mouth and nose is the most common side effect recorded with clonidine administration. Dizziness, headache and fatigue are frequently mentioned, as well as anorexia, nausea, constipation and even pseudo-obstruction (94 ), anxiety, depression, drug fever and rashes. Side effects occur in 50—70% of the patients treated and are in some 20% the reason for discontinuation of therapy (3 , 13, 83 ). 

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