Hypotension clonidine

Glonidine. Clonidine decreases blood pressure, heart rate, cardiac output, stroke volume, and total peripheral resistance. It activates central a2 adrenoceptors ia the brainstem vasomotor center and produces a prolonged hypotensive response. Clonidine, most efficaciously used concomitantly with a diuretic in long-term treatment, decreases renin and aldosterone secretion. 

When either drug is administered with diuretics and other hypotensives, an increased hypotensive effect may occur. When labetalol is administered with cimetidine, the effects of labetalol are increased. Halothane increases the effects of labetalol. When carvedilol is administered with the antidiabetic drugs, there is an increased effectiveness of the antidiabetic drugs. There is an increased effectiveness of clonidine when carvedilol is administered with clonidine There is an increased serum level of digoxin when digoxin is administered with carvedilol. 

The hypotensive action of clonidine could not be explained satisfactorily by effects on the peripheral circulation. Numerous studies therefore considered the possibility of an effect on the central nervous system. Investigations performed on spinalized animals could... 

The fact that the modes of action of clonidine and a-methylnoradrenaline are similar to the mode of action of the physiological transmitter noradrenaline indicates the importance of the role of the latter in the central control of blood pressure. It may be mentioned that 1-dopa too, the precursor of noradrenaline, penetrates the blood-brain barrier and causes hypotension and bradycardia after systemic administration, when do-... 

Figure 24. Hypotensive activity of clonidine derivatives with annel-lated hetero-rings...

Clonidine is a selective o -adrenergic agonist. Clonidine has expressed hypotensive action, which is associated with a reduction of general peripheral vascular resistance, reduced frequency of cardiac beats, and a reduction of cardiac output. The mechanism of action of clonidine is caused by stimulation of o -adrenoreceptors of the inhibitory structures of the brain as well as a reduction of sympathetic impulses to the blood vessels and brain. 

Clonidine is a selective Oj-adrenergic agonist that exhibits pronounced hypotensive action that is associated with a reduction of overall peripheral vascular resistance, decline in frequency of cardiac contraction, and reduced cardiac output. Clonidine is the drug of choice for treating various degrees of hypertension when used in combination with oral diuretics. 

Hypotension Tizanidine is an 2-adrenergic agonist (eg, clonidine) and can produce... 

Clonidine and other imidazoline compounds have also been shown to reduce muscle spasms by their central nervous system activity. Tizanidine is perhaps the most thoroughly studied clonidine analog. It is an agonist at a2-adrenergic receptors, but reduces spasticity at doses that result in significantly less hypotension than clonidine. 

Geriatric Considerations - Summary The alphaj-adrenergic agonist effect of tizani-dine lowers blood pressure in a manner similar to clonidine but is less potent. Older adults are at risk of hypotension and when discontinued, this drug should be tapered to avoid hypertensive rebound. 

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

Clonidine TCA postsynaptic a - adrenergic receptor antagonism blocks the agonist effect of clonidine Decrease in hypotensive effect of clonidine can be seen within days Increased doses of clonidine to continue van Zwieten, 1975... 

Beta-blockers interact with a large number of other medications. The combination of beta-blockers with calcium antagonists should be avoided, given the risk for hypotension and cardiac arrhythmias. Cimetidine, hydralazine, and alcohol all increase blood levels of beta-blockers, whereas rifampicin decreases their concentrations. Beta-blockers may increase blood levels of phenothiazines and other neuroleptics, clonidine, phen-ytoin, anesthetics, lidocaine, epinephrine, monoamine oxidase inhibitors and other antidepressants, benzodiazepines, and thyroxine. Beta-blockers decrease the effects of insulin and oral hypoglycemic agents. Smoking, oral contraceptives, carbamazepine, and nonsteroidal anti-inflammatory analgesics decrease the effects of beta-blockers (Coffey, 1990). 

Clonidine 0.003-0.01 bid or tid Tourette s syndrome ADHD Aggression/self-abuse Severe agitation Withdrawal syndromes Sedation (very frequent) Hypotension (rare) Dry mouth Confusion (with high dose) Depression Rebound hypertension Localized irritation with transdermal preparation... 

Guanfacine 0.015-0.05 Once, bid or tid Same as clonidine Less sedation, hypotension... 

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