From ExPat blog about the highway from Santiago to David:
I traveled the Pan American Highway from Santiago to David last weekend. It is open all the way but is only two lanes; one each way. There are only a few short areas of alternating one lane only. From Santiago to the checkpoint in Chiriquí Provence the road is bad, mostly unrepaired old road. It is open but very rough. After the checkpoint to David it is mostly one side or the other of the new road. There are some rough "crossovers". Also there are a few spots where the second double lane needs to be cut and graded. Looks like a lot of four lane "could" be open soon. Took the "by-pass" through Soná on the way back to avoid the rough part. Except for the rain it would have been a beautiful drive. I got lost in Santiago and took a while to find the Pan American there. I needed a dedicated map of Santiago.
Comment from another ExPat who lives in Chiriquí
It will be a number of years yet before that construction is completed. Santiago to David is 6 times the distance from David to Boquete. It took 2 years to finish the double laning from David to Boquete. I expect another 5 years before completing. Rivers run through in many areas as the water runs from the mountains to the oceans. Bridges of all sizes are being built as a result. It is quite a landscape change but a much anticipated one..........
Map of Panama showing Santiago to David: https://firstname.lastname@example.org,-81.7389944,10.69z