Manipulating the dose of lithium in a capsule in which lithium is contained: For some people, a high standard capsule containing even 150mg, can produce adverse effects upon ingestion (the biochemistry of that I don't know, but have always experienced, esp. upon discontinuation and long-term use).
At first, I tried cutting the cap, which as difficult and required recapping-- time consuming and requisition of fine dexterity to get the right amount, e.g. reduce 300mg to 100mg or 50mg.
So, I found another method: used a pin such as found in a sewing box, and pierce the top of of the capsule; be careful not pierce more than one hole as this will be necessary for pressure. Squeeze the capsule and watch the powder burst out, and holding it against a light, note how low the powder content reached a fraction of the capsule. Measure the fractions of the capsule by eye.
This way you can swallow the capsule without destroying the stomach-protective exterior as may be done by cutting it. Light will be needed to shine through the capsule to detect the amount that has been reduced through pressure squeezing. Hope this helps, a smaller amounts, at time intervals may reduce tremor, and other adverse effects.
Hope it works for you