Nitroprusside adverse effects

Hypotension is an important dose-limiting adverse effect of nitroprusside and other vasodilators. Therefore, nitroprusside is primarily used in patients who have a significantly elevated SVR and often requires invasive hemodynamic monitoring. 

Nitroprusside is the agent of choice for minute- to-minute control in most cases. It is usually given as a continuous IV infusion at a rate of 0.25 to 10 mcg/kg/min. Its onset of hypotensive action is immediate and disappears within 1 to 2 minutes of discontinuation. When the infusion must be continued longer than 72 hours, serum thiocyanate levels should be measured, and the infusion should be discontinued if the level exceeds 12 mg/dL. The risk of thiocyanate toxicity is increased in patients with impaired kidney function. Other adverse effects include nausea, vomiting, muscle twitching, and sweating. 

Nitroprusside [nye troe PRUSS ide] is administered intravenously, and causes prompt vasodilation, with reflex tachycardia. It is capable of reducing blood pressure in all patients, regardless of the cause of hypertension. The drug has little effect outside the vascular system, acting equally on arterial and venous smooth muscle. [Note Because nitroprusside also acts on the veins, it can reduce cardiac preload.] Nitroprusside is metabolized rapidly (t1/2 of minutes) and requires continuous infusion to maintain its hypotensive action. Sodium nitroprusside exerts few adverse effects except for those of hypotension caused by overdose. Nitroprusside metabolism results in cyanide ion production, although cyanide toxicity is rare and can be effectively treated with an infusion of sodium thiosulfate to produce thiocyanate, which is less toxic and is eliminated by the kidneys (Figure 19.14). [Note Nitroprusside is poisonous if given orally because of its hydrolysis to cyanide.]... 

Several older drugs are powerfully vasodilating, but precluded from routine use in hypertension by their adverse effects. Minoxidil and nitroprusside still have special indications. 

Discuss the limiting factors (with regard to adverse effects) to administration of sodium nitroprusside. 

The most clinically important adverse effects of sodium nitroprusside are profound hypotension and the accumulation of cyanide and thiocyanate. Thiocyanate may accumulate in the blood of patients receiving sodium nitroprusside therapy, especially in those with impaired renal function. Thiocyanate is mildly neurotoxic at serum concentrations of 60 pg/mL and may be life-threatening at concentrations of 200 pg/mL. Other adverse effects of thiocyanate includes inhibition of both the uptake and binding of iodine producing symptoms of hypothyroidism. 

III. Clinical presentation. The most common adverse effect of nitroprusside is hypotension, which is often accompanied by refiex tachycardia. Peripherai and cerebrai hypoperfusion can iead to iactic acidosis and aitered mentai status. 

The interactions of ergot derivatives with erythromycin and troleandomycin are well documented, well establish, and clinically important, whereas information about clarithromycin appears to be eonfined to three possible cases and that relating to oleandomycin to one case. There are no adverse reports about midecamycin, but it is expected to interact similarly. The concurrent use of all of these macrolides and ergot derivatives should be avoided. Some of the cases cited were effectively treated with sodium nitroprusside or naftidrofuryl oxalate, with or without heparin. "" " Spiramycin, and josamycin would not be expected to interact because they do not inhibit CYP3A4. However, there is one unexplained and unconfirmed report of an interaction with josamycin. "... 

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