One of the drawbacks with pharmaceuticals is that they come with possible adverse side effects. It sounds like your blood pressure medication needs to be adjusted.
Another drawback of pharmaceuticals is that they block the body's ability to regulate its own functions the way it was designed to do. High blood pressure is the body's attempt to protect itself from cell damage due to chronic dehydration.
When you don't properly replace the approximate 2 quarts of water that you lose every day, the body will start retaining salt to absorb water from food. This water gets filtered and injected into the dehydrated cells using a process called reverse osmosis.
Reverse osmosis requires pressure to force the salty water through minute holes in the cell's membrane to filter out the salt. The pressure needed for this comes from the raised blood pressure (that you take the medications for).
The role of medication in this issue is, it blocks the signals produced by histamine that lets the brain know that a water deficiency exists. The brain then gives you a recognizable symptom to let you know that you need to drink water - in this case, high blood pressure. With the signal from histamine blocked, the brain is fooled into thinking that the problem has been resolved, so it turns off the symptom.
Once the medications wear off, however, the signal from histamine is once again able to reach the brain and the brain responds by turning the symptom on again, creating an endless on/off cycle that never gets resolved because medications can't cure thirst - only water can.