Picniciple Of Toxicology | Chronopharmacology | Unit 5 Pharmacology 6th Semester

The lecture begins with an introduction to toxicology as the branch of pharmacology studying harmful and adverse effects of drugs and chemical products on the body. The instructor credits Paracelsus and Mathieu Joseph Bonaventure Orfila as fathers of modern toxicology. Toxicology types are categorized as acute (effects within 24 hours), sub-acute (effects appearing around 90 days), and chronic (effects developing over 90 days to years), with examples like mercury poisoning, heavy metal exposure, and long-term smoking.

The lecture then covers genotoxicity, explaining how toxic agents like radiation, chemicals, or viruses damage DNA through strand breaks, base changes, or cross-linking, potentially leading to mutations, cancer, autoimmune disorders, or cell death. Carcinogenicity is explained as DNA damage that activates oncogenes and suppresses tumor suppressor genes, leading to uncontrolled cell division and metastasis, treated with chemotherapy, radiotherapy, and surgery. Teratogenicity describes how toxic substances cross the placental barrier to harm fetal development, causing birth defects, growth delays, or miscarriage, with folic acid and iodine supplementation recommended for pregnant women. Mutagenicity covers how mutagens alter DNA sequences to cause permanent genetic mutations, linked to cancer and hereditary disorders.

The poisoning section covers general principles including ABC (airway, breathing, circulation) stabilization, activated charcoal administration, gastric lavage, urinary alkalinization, and hemodialysis. Specific poisonings discussed include: barbiturate poisoning (CNS depressant overdose causing respiratory depression and coma, treated with activated charcoal and supportive care); morphine poisoning (opioid overdose with naloxone as antidote); organophosphorus poisoning (acetylcholinesterase inhibition causing SLUDGE symptoms — salivation, lacrimation, urination, defecation, GI upset, emesis — treated with atropine); lead poisoning (organ damage especially in children, treated with chelation therapy); mercury poisoning (oxidative stress and organ damage, treated with chelation); and arsenic poisoning (energy disruption and nerve damage, treated with chelation therapy).

The final section covers chronopharmacology, introduced by Halberg in 1960, which studies how drug effects vary according to biological timing and body rhythms, especially the circadian rhythm. Biological rhythms are classified as circadian (24-hour cycles like sleep-wake, hormone secretion), ultradian (less than 24 hours, like heartbeat and breathing), and infradian (more than 24 hours, like the 28-day menstrual cycle). Chronotherapy applies this knowledge by administering medications at optimal times — asthma inhalers at night, antihypertensives in the morning, statins at night, and anti-inflammatories in early morning — to maximize efficacy and minimize side effects.