Nifedipine is in a group of drugs called calcium channel blockers. In high blood pressure, it normalizes the blood pressure by relaxing the blood vessels to reduce the pressure on them, thereby improving the blood flow in the body. The enhanced blood flow in the body further relaxes the heart muscles by reducing the workload on the heart. It also improves the oxygen flow in the body, thereby, preventing any heart-related chest pain.

Nifedipine is used to treat hypertension (high blood pressure) and angina (chest pain).

 swelling;
 flushing (warmth, redness, or tingly feeling);
 headache, dizziness;
 nausea, heartburn; or
 feeling weak or tired.
 allergic reaction (hives, difficult breathing, swelling in your face or throat)
 severe skin reaction (fever, sore throat, burning eyes, skin pain, red or purple
skin rash with blistering and peeling).

A sudden drop in your blood pressure may occur, especially when you first start
taking Nifedipine. To lower the chance of feeling dizzy or passing out, rise slowly if
you have been sitting or lying down.
It can cause ankle or foot swelling. To reduce the swelling, raise your legs while you
are sitting down. Talk to your doctor if it does not go away.
It may cause dizziness. Do not drive or perform any activity that requires mental
focus until you know how Nifedipine affects you. 
Inform your doctor if you are pregnant, planning a pregnancy or breastfeeding.