Male patient aged 68 years is evaluated for high B. P. He gets anginal pain provoked by physical exertion rapidly controlled by sublingual nitroglycerine. His BP reading is 160/110. He is advised 60 mg nifidipine in 3 divided dosage.

He develops flushing, dizziness and nervousness within 30 minutes of taking the drug and these symptoms persits for 1 hour. After starting nifidepine anginal episodes have increased. How nifidipine is responsible for new development of flushing and dizziness?