Dilute 20 mg (1 vial of reconstituted hydralazine solution in 1 ml of water for injection) in 9 ml of 0.9% sodium chloride, to obtain 10 ml of solution containing 2 mg/ml. Administer 5 mg (2.5 ml of the diluted solution) over 2 to 4 minutes. Check BP for 20 minutes. If BP remains uncontrolled, repeat injection.Click to see full answer. Then, how long does it take to get used to hydralazine?Peak blood levels of hydralazine are usually reached one to two hours after oral hydralazine; sooner if injectable hydralazine is used. The maximal blood pressure lowering effect is seen 10 to 80 minutes after hydralazine injection; data is not available regarding peak blood pressure lowering effects of the tablets. how do you stop hydralazine? Don’t stop taking hydralazine suddenly. Doing so may lead to uncontrolled high blood pressure. This can put you at a higher risk for heart problems, such as chest pain or a heart attack. If you need to stop taking this drug, your doctor will slowly decrease your dose over two weeks. Likewise, when should you not give hydralazine? If high blood pressure is not treated, it can cause serious problems such as heart failure, blood vessel disease, stroke, or kidney disease. It is best to take your medicine on an empty stomach, 1 hour before or 2 hours after meals.What time of day should you take hydralazine?If you are to take a single dose a day, take it in the morning after breakfast. If you are to take more than one dose a day, take the last dose no later than 6 p.m., unless otherwise directed by your doctor.