I believe it's safer to swallow with head level or tilted forward because tilting back tends to disrupt the epiglottis' seal over the trachea, potentially allowing aspiration of liquids and/or solids (which leads to pneumonia). Forward tilt aids the epiglottis in making a good seal of the windpipe!
http://psychology.wikia.com/wiki/SwallowingIf you look at the following animation, you can see that by tilting head back, the larynx flap, just below the epiglottis, may protrude and guide the first part of the food into the trachea....
http://hopkins-gi.org/multimedia/database/intro_250_Swallow.swfWhat I do is sip some water, place or fling the pill(s) to the back, sip some more water, tilt head slightly back to let water flow there, then go level and swallow several times. If I can sense a pill still there, I sip more water and swallow some more.
