Tachycardia minoxidil

Direct Vasodilators Isosorbide dinitrate 20 mg and hydralazine 37.5 (BiDil) 1-2 tablets three times a day Minoxidil (Loniten) Hydralazine Heart failure (isosorbide dinitrate + hydralazine in African-Americans) A-HeFT66 Edema (minoxidil) Tachycardia Lupus-like syndrome (hydralazine) ... 

In multidrug therapy, it is necessary to consider which agents rationally complement each other. A p-blocker (bradycardia, cardiodepression due to sympathetic blockade) can be effectively combined with nifedipine (reflex tachycardia), but obviously not with verapamil (bradycardia, cardiodepression). Monotherapy with ACE inhibitors (p. 124) produces an adequate reduction of blood pressure in 50% of patients the response rate is increased to 90% by combination with a (thiazide) diuretic. When vasodilators such as dihydralazine or minoxidil (p. 118) are given, p-blockers would serve to prevent reflex tachycardia, and diuretics to counteract fluid retention. 

Minoxidil is a peripheral vasodilator that directly relaxes vascular smooth musculature, thus, lowering systolic and diastolic pressure. Its action is linked to the activation of calcium channels. Open calcium channels cause hyperpolarization of smooth muscle cells, which in turn, reduces the flow of calcium ions into the cell, which is necessary for supporting vascular tonicity. However, when taking minoxidil, tachycardia, elevated renin secretion, and water and sodium ion retention all appear simultaneously with hypotension. Because of potentially serious side effects, it is used only for severe hypertension that does not respond to treatment with other drugs, and absolutely in combination with two other antihypertensive drugs. A synonym of this drug is loniten. 

Beta-biockers/Other sympathetic nervous system suppressants - When beginning therapy, the -blocker dosage should be equal to 80 to 160 mg/day propranolol in divided doses. If -blockers are contraindicated, use methyidopa 250 to 750 mg twice daily give for at least 24 hours before starting minoxidil due to delay in onset. Clonidine may also be used to prevent tachycardia induced by minoxidil usual dosage is 0.1 to 0.2 mg twice daily. 

Tachycardia/Angina Minoxidil increases heart rate this can be prevented by coadministration of a -adrenergic blocking drug or other sympathetic nervous system suppressants. In addition, angina may worsen or appear for the first time... 

Oral minoxidil administration should be closely monitored, usually given with a beta-blocker to prevent tachycardia and a diureticto prevent fluid accumulation. 

Tachycardia, palpitations, angina, and edema are observed when doses of 3 blockers and diuretics are inadequate. Headache, sweating, and hypertrichosis, which is particularly bothersome in women, are relatively common. Minoxidil illustrates how one person s toxicity may become another person s therapy. Topical minoxidil (as Rogaine) is used as a stimulant to hair growth for correction of baldness. 

Hydralazine Causes nitric oxide release Vasodilation reduce vascular resistance arterioles more sensitive than veins reflex tachycardia Hypertension minoxidil also used to treat hair loss Oral Toxicity Angina, tachycardia Hydralazine Lupus-like syndrome... 

Although vasodilators are effective in lowering blood pressure, these drugs are associated with a number of adverse effects. Reflex tachycardia often occurs because baroreflex responses attempt to compensate for the fall in vascular resistance that these drugs produce. This side effect is analogous to the increased heart rate occurring when alpha blockers are used to decrease peripheral vascular resistance. Other common reactions include dizziness, postural hypotension, weakness, nausea, fluid retention, and headache. Minoxidil also increases hair growth on the face, ears, forehead,... 

Direct vasodilators frequently produce baroreflex-induced tachycardia, but rarely orthostatic hypotension. They are usually prescribed with a beta blocker or a centrally acting antihypertensive to minimize the reflex increase in heart rate and cardiac output. It should be noted that another member of the directly acting class of antihypertensives is minoxidil. This potent, long-acting drug has gained considerable notoriety for its use as a topical hair-restorer. Oral use can result in hirsutism (unwanted hair growth over the face as well as other parts of the body). 

Minoxidil is a vasodilator selective for arterioles rather than for veins, similar to diazoxide and hydralazine. Like the former, it acts through its sulphate metabolite as an ATP-dependent potassium channel opener. It is highly effective in severe hypertension, but causes increased cardiac output, tachycardia, fluid retention and hypertrichosis. The hair growth is generalised and although a cosmetic problem in women, it has been exploited as a topical solution for the treatment of baldness in men. 

A 26-year-old woman took 60 ml of minoxidil solution 5% and 1 hour later developed hypotension (75/ 40 mmHg) and tachycardia (130/minute). She was... 

The diamino pyrimidine derivative minoxidil became available in the United States in 1980. It is probably the most potent oral vasodilator in use, making it a very important drug in severe hypertension, especially when refractory to other agents. It is best used in combination with a 3-blocker (to prevent reflex tachycardia) and a diuretic (to prevent fluid accumulation). 

Minoxidil Tachycardia aggravation of angina marked fluid retention possible pericardial effusion hair growth on face and body ... 

Minoxidil Marked salt and water retention, very marked tachycardia Hirsutism, pericardial effusion... 

Drugs that dilate blood vessels by acting directly on smooth muscle cells through nonautonomic mechanisms are useful in treating many hypertensive patients. Three major mechanisms are utilized by vasodilators release of nitric oxide, opening of potassium channels (which leads to hyperpolarization), and blockade of calcium channels (Table 11-3). Compensatory responses are marked for some vasodilators (especially hydralazine and minoxidil) and include salt retention and tachycardia (Table 11-2). 

A. Hydralazine and Minoxidil These older vasodilators have more effect on arterioles than on veins. They are orally active and suitable for chronic therapy. Hydralazine apparently acts through the release of nitric oxide. However, it is rarely used at high dosage because of its toxicity therefore, its efficacy is limited, fts toxicities include compensatory responses (tachycardia, salt and water retention Table 11-2) and drug-induced lupus erythematosus, which is reversible upon stopping the drug. However, this effect is uncommon at dosages below 200 mg/d. 

Marked tachycardia and fluid retention are compensatory responses usually seen with strong vasodilators. The fact that the unknown drug also increases hair growth points strongly at minoxidil. The answer is (C). 

However, the probable best usage of propranolol shall be its combination with an antihypertensive vasodilators e.g. hydralazine, minoxidil etc., to preferentially check and prevent the reflex tachycardia. ... 

C. Minoxidil. Two adults developed profound hypotension (with tachycardia) requiring pressor support following 1.3-g and 3-g ingestions from topical minoxidil solutions. 

Farrell SE, Epstein SK Overdose of Rogaine Extra Strength for Men topical minoxidil preparation. J Toxicol Clin Toxicol 1999 37(6) 781-783. [PMID 10584592] (Case report of 3-g overdose resulting in profound hypotension, prolonged tachycardia, and fluid overload leading to pleural effusions.)... 

Developments in clinically useful anti hypertensives - There has been a great deal of discussionis on work carried out to evaluate the therapeutic potential of combining a vasodilator with a 6-adrenoreceptor blocker in order to counteract the tachycardia associated with the former. The combination of hydralazine with propranolol (p.o.) is effective in hypertensive patients at doses which separately do not give a satisfactory hypotensive effect a similar situation holds for dihydralazine. Alprenolol (i.v.) also reduced the cardiac stimulation observed in normotensive and hypertensive patients after dihydralazine (i.v.). Minoxidil (PDP), in combination with propranolol and hydrochlorothiazide, appears to be more effective in refractory hypertensive patients than hydralazine. Practolol effectively blocks the tachycardia in normotensive dogs treated with hydralazine (i.v.) without potentiating the hypotensive effects, which suggests that tachycardia does not diminish the hypotensive effect of hydralazine. 

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