practice is in the use of nifedipine for the treatment of hypertension associated with autonomic dysreflexia in spinal cord injury. Early labor Nifedipine has been used frequently as a tocolytic (agent that delays premature labor). A Cochrane review has concluded that it has benefits over placebo or no treatment for prolongation of pregnancy. It also has benefits over beta-agonists and may also have some benefits over atosiban and magnesium sulfate, although atosiban results in fewer maternal adverse effects. No difference was found in the rate of deaths among babies around the time of birth, while data on longer-term outcomes is lacking. Other Raynaud's phenomenon is often treated with nifedipine. A 2005 meta-analysis showed modest benefits (33% decrease in attack severity, 2.8-5 reduction in absolute number of attacks per week); it does conclude that most included studies used low doses of nifedipine. Topical nifedipine has been shown to be as effective as topical nitrates for anal fissures. Nifedipine is also used in high-altitude medicine to treat high altitude pulmonary edema. Nifedipine is one of the main choices for the treatment of Prinzmetal angina due to its vasodilating effects on the coronary arteries. Other uses include painful spasms of the esophagus such as from cancer or tetanus. It is also used for the small subset of people with pulmonary hypertension. Finally, nifedipine can be used in the treatment of renal calculi, which are commonly referred to as kidney stones. Studies have indicated that it helps to relieve renal colic. However, alpha blockers (such as tamsulosin) have been described as being significantly better. Side effects Nifedipine rapidly lowers blood pressure, and patients are commonly warned they may feel dizzy or faint after taking the first few doses. Tachycardia (fast heart rate) may occur as a reaction. These problems are much less frequent in the sustained-release preparations of nifedipine. Extended release formulations of nifedipine should be taken on an empty stomach, and patients are warned not to consume anything containing grapefruit or grapefruit juice, as they raise blood nifedipine levels. There are several possible mechanisms, including the inhibition of CYP3A4-mediated metabolism. As calcium channel blocker, nifedipine has a risk of causing gingival hyperplasia Overdose A number of persons have developed toxicity due to acute overdosage with nifedipine, either accidentally or intentionally, and via either oral or parenteral administration. The adverse effects include lethargy, bradycardia, marked hypotension and loss of consciousness. The drug may be