🧪 NEW DRUG DEVELOPMENT AND PRECLINICAL TOXICITY STUDIES

-

By Dr. Sk Sabir Rahaman, MBBS, MD (Pharmacology), DFM(Family Medicine), FCFM, CCEBDM, CCLSD 

🌍 INTRODUCTION: WHY STUDY DRUGS BEFORE HUMAN USE?

Before a new drug is tested in humans, it must undergo preclinical studies in laboratory animals. These studies are done to:

  • Establish scientific rationale for safety

  • Determine safe dose ranges and routes of administration

  • Predict potential toxicities and side effects in humans

  • Comply with regulatory and ethical standards (GCP, GLP, CPCSEA/CCSEA guidelines in India)

⚖️ The ultimate goal: Protect human participants when clinical trials begin.

🔑 TYPES OF PRECLINICAL TOXICITY STUDIES

✅ General Rule: Preclinical toxicity testing must be done in two animal species — one rodent (rat/mouse) and one non-rodent (dog/monkey), using the intended human route (oral, IV, inhalation, etc.).

1. Acute Toxicity Studies

  • Purpose: To determine LD₅₀ (median lethal dose) and identify immediate toxic effects.

  • Method:

    • Animals receive a single dose or graded doses.

    • Monitored for 24–72 hours for mortality and clinical signs.

  • Outcome: Defines the safety margin and helps select the starting human dose (usually 1/100th of LD₅₀ in animals).

  • Example: A drug with LD₅₀ = 200 mg/kg in rats → starting human dose ≈ 2 mg/kg.

2. Subacute (Repeated-Dose) Toxicity Studies

  • Purpose: Detect cumulative toxicity and target organ damage.

  • Duration: 14–28 days.

  • Parameters Monitored:

    • Body weight, food/water intake

    • Hematology (Hb, WBCs), Biochemistry (liver enzymes, kidney function)

    • Histopathology of vital organs (liver, kidney, heart, lungs, etc.)

  • Outcome: Establishes:

    • Maximum Tolerated Dose (MTD)

    • No Observed Adverse Effect Level (NOAEL)

  • Clinical Tip: If hepatotoxicity appears in rats, then LFTs are monitored closely in Phase I human trials.

3. Chronic Toxicity Studies

  • Purpose: Assess long-term safety and simulate chronic human use.

  • Duration: 6–12 months (sometimes longer depending on intended therapy).

  • Animals: One rodent + one non-rodent species.

  • Monitoring: Same as subacute, but with more focus on:

    • Organ damage

    • Carcinogenic potential

    • Cumulative effects of repeated dosing

  • Example: Chronic NSAID exposure → renal papillary necrosis in animals → routine renal monitoring in patients.

4. Special Toxicity Studies

These assess genetic, reproductive, and developmental risks:

TypePurposeCommon Tests
MutagenicityDNA mutations & chromosomal damageAmes test, chromosomal assays
CarcinogenicityDetect cancer-causing potential2-year rodent studies
TeratogenicityFetal malformations (birth defects)Administered to pregnant animals
Reproductive ToxicityFertility, pregnancy, lactation effectsPre-mating to lactation studies

⚠️ Clinical Application: The thalidomide tragedy (causing birth defects) → made teratogenicity testing mandatory worldwide.

📊 HOW THESE STUDIES GUIDE HUMAN TRIALS

Study TypeHuman Application
Acute ToxicitySets initial human dose and emergency safety guidelines
Subacute ToxicityDefines short-term therapeutic window
Chronic ToxicityEssential for chronic diseases (HTN, diabetes, epilepsy)
Special ToxicityGuides use in pregnancy, pediatrics, cancer therapy

⚖️ REGULATORY & ETHICAL FRAMEWORK (INDIA)

  • Preclinical studies must follow Good Laboratory Practice (GLP).

  • Ethical oversight by CCSEA (formerly CPCSEA – Committee for the Control and Supervision of Experiments on Animals), Ministry of Environment, Forest & Climate Change, Govt. of India.

  • Mandatory approvals before starting:

    • Institutional Animal Ethics Committee (IAEC) approval

    • CCSEA registration of animal house

  • Only after preclinical package (toxicity + pharmacology) is complete → IND (Investigational New Drug) application is submitted to DCGI (CDSCO) for human trials.

📝 SUMMARY

  • Preclinical toxicity studies are mandatory before clinical trials.

  • Include acute, subacute, chronic, and special tests in at least two animal species.

  • Outcomes: MTD, NOAEL, organ-specific risks.

  • Guide dose selection, patient monitoring, and trial design.

  • Governed by GLP, IAEC, and CCSEA regulations in India. 



📘 Prepared by Dr. Sk Sabir Rahaman
📍 Specialist Family Physician | Consultant Pharmacologist | Lifestyle & Diabetes Expert

🌐 Visit My Website for  Articles & other Free PDFs and Resources

Comments

Post a Comment

Popular posts from this blog

🏥 Insulin Storage: Myths vs. Facts Every Diabetic Should Know

-
By Dr. Sk Sabir Rahaman, MBBS , MD (Pharmacology), DFM(Family Medicine), FCFM, CCEBDM, CCLSD   For millions living with diabetes, insulin is more than a medication — it’s a lifeline . However, widespread misconceptions about insulin storage often lead to avoidable panic, especially during heatwaves, power outages, or while traveling . 🚫 The Myth: "Insulin must always stay refrigerated" Many believe that insulin instantly loses effectiveness once it’s out of the fridge. This is not true — and can cause undue stress, particularly in hot climates like India or during journeys where refrigeration isn’t available. ✅ The Fact: Most insulin types tolerate room temperature According to World Health Organization (WHO) and insulin manufacturer guidelines : 🔹 Opened insulin vials or pens can be safely kept at room temperature (15–25°C / 59–77°F) for up to 28 days. That means: You don’t need to return it to the fridge every time after injection. It's safe fo...
Read more

🧴 TREATMENT OF POISONING – A COMPREHENSIVE OVERVIEW

-
By Dr. Sk Sabir Rahaman, MBBS , MD (Pharmacology), DFM(Family Medicine), FCFM, CCEBDM, CCLSD   🧪 Definition & Scope Toxicology : Branch of pharmacology dealing with harmful effects of chemicals on living organisms. Poisoning : Harmful effects caused by ingestion, inhalation, dermal exposure, or injection of toxic substances (drugs, pesticides, household chemicals, industrial agents, venoms). Medico-legal importance : All poisoning cases are medical emergencies. Must be reported to police/authorities (especially suicidal, homicidal, or accidental cases) under Indian law. 🛑 General Principles of Management (ABCDE of Toxicological Emergencies) A – Airway Ensure patency (tongue fall, aspiration common in comatose patients). Place in left lateral position to reduce aspiration. Intubate with cuffed endotracheal tube if airway compromised. Regular suction of secretions. B – Breathing Monitor with pulse oximetry and ABG. Give humidified oxy...
Read more

🌿 Rational Use of Medicines (RUM): A Guide for Safer and Smarter Prescribing

-
By Dr. Sk Sabir Rahaman, MBBS , MD (Pharmacology), DFM(Family Medicine), FCFM, CCEBDM, CCLSD   📍 Specialist Family Physician | Consultant Pharmacologist | Lifestyle & Diabetes Expert Medicines save lives, ease suffering, and improve health outcomes. But when they are used irrationally , they can cause more harm than good. The World Health Organization (WHO) emphasizes the importance of the Rational Use of Medicines (RUM) to ensure patient safety, treatment effectiveness, and cost efficiency. In this blog, we’ll explore what RUM means, why it matters, and how healthcare professionals can practice it effectively. 📌 What is Rational Use of Medicines? According to WHO: “Rational use of medicines requires that patients receive medications appropriate to their clinical needs, in doses that meet their individual requirements, for an adequate period of time, and at the lowest cost to them and their community.” In simple words: it’s about prescribing the right medicine, in t...
Read more