He's not wrong though. The difference between poison and medicine is often a matter of knowing when and how much to provide someone. I've seen more than one health care professional I know socially or am related to express the same "all medicine is poison but" phrase from earlier as a thing they were taught in school.
Just to put a point on it tons of people are on blood pressure meds that would knock most people right out (or worse) from hypotension if given and here are several examples of plants literally considered to be poison that are used in medicine and how.
Here are some examples of herbs once considered poison that are now used in medicine:
Belladonna (Deadly Nightshade)
- Active compounds: This plant contains tropane alkaloids, such as atropine and scopolamine. The name belladonna, meaning "beautiful lady," refers to its use by Italian Renaissance women who would use drops to dilate their pupils, which was considered an attractive feature.
- Medicinal uses:
- Ophthalmology: Dilates pupils for eye exams and surgery.
- Gastrointestinal issues: Hyoscyamine is used to treat cramps associated with irritable bowel syndrome (IBS).
- Motion sickness: Scopolamine is available in patches to prevent motion sickness.
- Antidote: Atropine serves as an antidote for some nerve agent and insecticide poisonings.
Foxglove
- Active compound: The leaves of the foxglove plant contain cardiac glycosides, primarily digoxin.
- Medicinal uses:
- Heart failure: Digoxin is used to improve the strength and efficiency of heart muscle contractions.
- Arrhythmias: It is also prescribed to control the rate and rhythm of an irregular heartbeat, such as atrial fibrillation.
Oleander
- Active compound: Oleander contains toxic cardiac glycosides, such as oleandrin, which are similar to the active chemical in foxglove.
- Medicinal uses: While the plant is highly poisonous and unsafe for self-medication, researchers are investigating oleandrin for potential anticancer properties. Lab studies have shown that it may suppress cancer cell growth, but human trials are limited.
Aconite (Wolfsbane)
- Active compounds: This plant contains diterpenoid alkaloids, such as aconitine, which are highly toxic, especially to the nervous system and heart.
- Medicinal uses:
- Traditional Chinese Medicine (TCM): After extensive processing to reduce its toxicity, aconite has been used for centuries to treat pain, inflammation, and heart conditions.
- Analgesic: Less toxic derivatives of the alkaloids have shown analgesic (pain-relieving) and anti-inflammatory properties.
Autumn Crocus
- Active compound: The autumn crocus contains the powerful alkaloid colchicine, which inhibits cell division and can be lethal in high doses.
- Medicinal uses:
- Gout: Colchicine is a mainstay for treating and preventing gout attacks, as it reduces the inflammation caused by uric acid crystal deposits.
- Familial Mediterranean Fever (FMF): It is also used to prevent inflammation-related attacks in FMF, a genetic inflammatory disorder.
Nux Vomica (Poison Nut)
- Active compounds: The seeds of the nux vomica tree contain strychnine and brucine, two toxic alkaloids that affect the nervous system.
- Medicinal uses:
- Traditional Medicine: Processed seeds have been used in Ayurvedic and Traditional Chinese Medicine for conditions such as rheumatic pain, nervous system disorders, and gastrointestinal issues.
- Neurological research: The controlled use of these compounds has aided in research on how the nervous system functions.