“少阴病，二三日不已，至四五日，腹痛，小便不利，四肢沉重疼痛，自下利者，此为有水气。
其人或咳，或小便利，或下利，或呕者，真武汤主之。”
One way to interpret this is that you use 真武汤 only if on top of the 水气 problem, there is cough, urine passing smoothly, diarrhea, vomit. This makes sense because you can think of the 附子 in 真武汤 maintaining a high-enough level of arterial blood pressure, useful especially if you’ve just lost fluids via cough, […]
From 《金匮要略》：“假令瘦人，脐下有悸，吐涎沫而癫（we can treat this as [真页](pronounced chen) which means 顶）眩，此水也，五苓散主之。”
Note that in WLS is LGZGT which is indicated for 目眩, but note that WLS does not have 甘草, and we now know that 甘草 can facilitate water and sodium retention.
In 麻黄汤，the ratio of MH:GZ:GC is 3:2:1 两.
In 小青龙汤, 麻黄 remains at 3两.
Only in 大青龙汤 and 越婢汤 do we see a doubling of 麻黄. See here for more on the quantities difference in 麻黄汤 variants in SHL.
半夏泻心汤 (7 flavors)
生姜泻心汤 (8 flavors)
甘草泻心汤 (6 flavors)
旋覆代赭汤：旋覆代赭 replaces 黄芩黄连；生姜 instead of 干姜
黄连汤：桂枝 replaces 黄芩（“腹中痛”）
小柴胡汤：柴胡 replaces 黄连
Plays on the idea:
小陷胸汤：黄连、半夏、瓜蒌实 - but no 甘补 herbs are included
to be continued…
Just for reference, remember that in 麻黄汤, the 麻：桂：草 portions are 3liang:2liang:1liang
- - -
麻黄汤：麻黄 (3liang), 桂枝 (2liang)
越婢加半夏汤：麻黄 (6liang), 石膏 (8liang)
小青龙汤：麻黄 (3liang), 桂枝 (3liang)
小青龙加石膏汤：麻黄 (3liang), 桂枝 (3liang), 石膏 (2liang)
麻杏石甘汤：麻黄 (4liang), 石膏 (8liang)
厚朴麻黄汤：麻黄 (4liang), 石膏 (如鸡子大)
大青龙汤：麻黄 (6liang), 桂枝 (2liang), 石膏 (如鸡子大)
