**Bioprospecting**

This is the screening of a large number of natural products, chemical entities, large libraries of peptides, nucleic acids and other organic molecules for biological activity. This approach may lead to identification and development of new drug molecules.

**Disease model Animal model Route of administration Physiological**

Parenteral

e. GIT effects Rat Oral GIT motility and secretions

If an agent possesses useful activity it would be further studied for possible adverse effects on other major organs. These studies might suggest the need for further chemical modification to

The data from animal studies form a basis for the calculation of the initial or starting doses to be used in the subsequent clinical studies. The human equivalent dose calculations for the maximum recommended dose are normally based on either the body surface area or body weight. The candidate drugs that survive initial screening and profiling must be carefully evaluated for potential risks before and during clinical testing. The main types of evaluation

This involves looking at the effects of large single doses of therapeutic agent. Acute toxicity studies are usually performed in animal models such as mice and rats. These studies enable

This is similar to acute toxicity but measures the effects of multiple doses based on expected duration of clinical usage. It entails haematological, histology and electron microscope studies to identify organs which might be affected by toxicity. It usually lasts between one to three

These studies are required when the drug is intended to be used in humans for prolonged periods. The goals of this investigation are mostly similar to those of sub-acute toxicity.

investigators to correlate any observed effects with the systemic level of the drug.

months. This enables the selection of putative compounds for subsequent studies.

Dog/guinea pig Parenteral Respiratory rate and

c. CNS Mouse, rat Parenteral Degree of sedation

a. Blood pressure Hypertensive rat

b. Cardiac effects Dog (conscious)

d. Respiratory effects

**13.3. Preclinical trials**

**Acute toxicity**

**Sub-acute toxicity**

**Chronic toxicity testing**

(conscious)

**Table 2.** Putative animal models used in studying effects of drugs

needed from safety and toxicity studies include:-

achieve desirable pharmacokinetic/pharmacodynamic properties.

Dog (anesthetized)

**measurements**

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(cardiac output)

amplitude

Parenteral Systolic/diastolic

Introduction to Biochemical Pharmacology and Drug Discovery

Oral Electrocardiography
