Abstract
The connection between therapeutics and toxicology is characterized by a key scientific concept; the same drug can act as either a toxicant or a drug with respect to the dosage, exposure circumstances, susceptibility in the biology, and clinical circumstances. This review discusses that fine line incorporating the toxicological and pharmacological views of dose-response relationship, pharmacokinetics and toxicokinetics, molecular mechanisms of action and the therapeutic window. It covers the origins of therapeutic benefit and toxic harm when interacting with shared cellular and molecular targets, such as receptors, enzymes, and nucleic acids and highlights the key mechanisms of toxicity including oxidative stress, mitochondrial dysfunction, apoptosis, and necrosis. The review also discusses the target specificity, controlled dosing and optimization of exposure used to differentiate therapeutic action and toxicity. The cases of classical and modern toxins such as digoxin, arsenic trioxide, botulinum toxin, chemotherapeutic agents, opioids, and so on, where the opposite to therapy is toxicity but, in these circumstances, its biological cause, can confirm that the latter is not the opposite of the former. The regulatory approval, safety margins, pharmacovigilance, medication errors, risk of overdose, and the increasing role of personalized medicine to decrease adverse outcomes are also discussed in the article. The developmental trends to consider in the future, including precision toxicology, use of artificial intelligence in predicting toxicity, designing safer drugs, and use of biomarker-based approaches in evaluating drug safety are discussed as new methods of enhancing the decision-making process in therapy. In general, the review finds that dose is the conclusive determinant of is-the-agent-healing medicine or is-the-agent-toxic medicine and that the balance between therapeutic good and toxic evil requires an understanding of the mechanisms that goes deep.