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桂枝甘草汤：

“发汗过多，其人叉手自冒心，心下悸，欲得按者，桂枝甘草汤主之。”

Here we learn about the most valuable players used in treating cardiovascular problems: 桂枝 and 炙甘草.

It’s weak heart-yang that’s the problem, usually understood as the path leading heart failure. Both of the herbs are warm and acrid and can boost yang energy. That’s why why use the phrase “辛甘化阳” to describe this herb combination. 桂枝 can 通阳，which i understand physiologically as the result of its effect on improving circulation, through dilation of blood vessels especially in the coronary and brain vessels. 甘草 (licorice) is heavy in polysaccarides, which may explain its ability to tonify qi and hence yang.

桂枝甘草龙牡汤：

“火逆下之，因烧针烦躁者，桂枝甘草龙骨牡蛎汤主之。”

Here’s we see a case of agitation（烦躁）due to deficiency. Very interesting.

As for 龙骨 and 牡蛎. I tend to see them as cns ‘downers.’ You add them to calm the person down, whether it’s in 柴胡龙牡汤，桂甘龙牡汤 or 桂枝龙牡汤 - at least that howI see these two herbs now.

桂枝去芍药加蜀漆牡蛎龙骨救逆汤：

Very long name. This formula is a 桂枝汤+/—, but really it’s the above decoction （桂枝甘草龙牡汤）plus 姜、枣 plus 蜀漆. The 蜀漆 is to get rid of phlegm (涤痰化饮), and to me this addition means that the situation is worse than in the 桂枝甘草龙牡汤 case. 姜、枣 is keep the spleen-stomach in good order.

Note that 芍药 is not in the formula. We can look at 桂枝去芍药汤 for the reason why. In 桂枝去芍药汤，we have something like 胸痹 (see  “脉促胸满”). Some books explain that this is because 芍药 is cold in nature, and hence not used.

桂枝加桂汤：

Here, we have extra 桂枝 added on. For what?

For 奔豚，the “running piglet.” Mr. Zhang explains:

“气从少腹上冲心者…”

Once again, a heart issue. Solved by even more 桂枝.

苓桂甘枣汤：

Here, we have 桂枝甘草汤 as the base formulua. 茯苓 and 大枣 are added, and remember that it is here that you have half jin（半斤）of 茯苓.  Think of these two as herbs that help you calm down. For what?

Well, the quote below will show that the problem is a twitching (I suspect) below the belly button and a feeling that the running piglet is going to begin running.

“其人脐下悸者，欲作奔豚…”

Summary：

So in total we have 5 formulas for helping boost heart yang. They differ in their use but are from the same family headed by 桂枝 and甘草.