A cheap plant oil whose single unusual fatty acid switches on one muscle receptor. Taken orally it empties the bowel within hours and contracts the uterus, so unsupervised use in pregnancy is the most hazardous setting. On the eyelids it eases gritty, inflamed lid conditions. Cramping and nausea follow nearly every full oral dose. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Serum potassium | 4.0–4.5 mmol/L | Purgation's first casualty; low values drive weakness and arrhythmia |
| Serum sodium | 138–142 mmol/L | Detects the volume depletion that follows heavy fluid loss |
| Red blood cell magnesium | 4.2–6.8 mg/dL | Lost with potassium and must be corrected first, or potassium will not rise |
| Serum bicarbonate | 24–28 mmol/L | Rising values flag the metabolic alkalosis of repeated purgation |
| Estimated glomerular filtration rate | Above 90 mL/min/1.73 m² | Kidney filtration sets the whole safety margin for fluid shifts |
| 25-hydroxyvitamin D | 40–60 ng/mL | Stands in for fat-soluble vitamin status, which repeated purgation erodes |
| Bristol Stool Form Scale | Type 3–4 | The direct efficacy readout for any laxative use |
| Tear break-up time | Above 10 seconds | The objective measure of tear film stability castor oil is proposed to improve |
| Ocular Surface Disease Index | Below 13 points | The validated symptom score used as the primary endpoint in the eyelid trials |
Cadence: A single oral dose in a healthy adult needs no laboratory work. Baseline panel where oral use is repeated, a diuretic, digoxin or a corticosteroid is on board, or kidney function is reduced; repeat electrolytes and kidney function one week after any month with more than two oral doses, then every six to twelve months if that pattern continues. Ocular measures at baseline, four weeks, then every three to six months.