If your husband is on opiate pain medications, they will cause low bp as they depress the central nervous system which slows the cardiovascular system. The big reason you shouldn't drink alcohol when you're on an opiate. Fentanyl is notorious for it as is hydro.

A great way to monitor it is just to pinch the tip of your finger and watch how fast the color returns to it. IF he is on the fentanyl patch, watch where you place it and never put it in an area that gets direct heat by showering/bathing or when he sits or lays down. They are heat activated and a raise in body temp will release more medication into his blood stream. One of the signs of this is dramatic decrease in blood pressure and could be an early sign of an overdose.

A great way to monitor this is by asking him if his extremities are cold and by pinching the end of the finger and seeing how long it takes for the color to return (capillary refill test). If his lips are blue, or his hands and feet are bluish...it's a good idea to take him to the ER. If not and it's just dizziness...just keep an eye on it.

I had the same issues when I was on fentanyl and it put me in the ER several times due to where I was placing my patches.

Hope that helps

Eric