TOKSIKOLOGI DAN TANAMAN OBAT

Aulanni’am & Tim TeachingProgram Kedokteran Hewan UB

What is toxicology?

Superman

The Mercury Cycle

toxic compounds

physical agents

toxicology …………

• Is the study of the harmful effects of chemicals and physical agents on living organisms

• Examines adverse effects ranging from acute to long-term

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toxicology …………

• Is used to assess the probability of hazards caused by adverse effects

• Is used to predict effects on individuals, populations and ecosystems

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These adverse effects may occur in many forms, ranging from immediate death to subtle changes not realized until months or years later. 

They may occur at various levels within the body, such as an organ, a type of cell, or a specific biochemical.

Sources of toxic compounds

Synthetic organic compound

1. Air, water, and food pollutantsAir- CO, oxides of nitrogen, oxides of sulfur, hydrocarbons and particulatesWater-agricultural chemicals including pesticides, herbicides, fugicides, nematocides, rodenticides, fertilizer Halogenated hydrocarbons- chloroform, dichloroethane, tetrachloride

Clorinated aromatics-PCB, TCDDDetergents-alkyl benzene sulfonates

2. Chemical additives in food

As preservatives-antibacterial, antifungal, or antioxidant

To change physical characteristics, taste, color, odor

.

3.Chemicals in work place Inorganics-metals and flurides, CO, etc. Organic compounds-aliphatic hydrocarbons (hexene) aromatic hydrocarbons (eg. benzene, toluene)

halogenated hydrocarbonsalcoholsestersorganometallicsamino compounds

.

4. Drugs of abuse

CNS depressants-ethanol,secobarbitalCNS stimulants-cocaine,

methamphatamine,nicotine, caffeine

Opioids-heroin, morphineHallucinogens-PCP, LSD,THC

5.Therapeutic drugs The danger to the individual depends on :

the nature of the toxic responsethe dose necessary to produce the toxic responsethe relationship between the therapeutic dose and the toxic dose

eg, anticancer drugs are carcinogensDiethylstilbestrol (DES)Thalidomide

Chloroquinol-SMON-subacute myelo-optic neuropathy

Methyldopa, chloropromazine, methotrexate

In general, toxic side effects are not common and may occur only in susceptible individuals or populations.

6. Pesticides

Classes Of Pesticides

Insecticides (kill insects)

• Organochlorines• Organophosphates• Carbamates• Synthetic Pyrethroids

Herbicides (kill plants) Rodenticides (kill rodents) Fungicides (kill fungus) Fumigants (kill whatever)

6. Pesticides

7. Solvents

8. Polycyclic aromatic hydrocarbons (PAH)

Incomplete combustion of organic materials, in smoke from wood, coal, oil, tobacco, in tar and broiled foods

Carcinogens

9. Cosmetics

Allergic reactions and contact dermatitis

Bromate, cold-wave neutralizer

Thioglycolates and tioglycerol-cold-wave lotion and depilatories

Sodium hydroxide-hair straighteners

Naturally occurring toxins

1. Mycotoxins2. Microbial toxins3. Plant toxins4. Animal toxins

"Toxin"=refers to toxic substances that are produced naturally

"Toxicant"=substance that is produced by anthropogenic origin  

An interdisciplinary field…………

Descriptive ToxicologyMechanistic ToxicologyRegulatory Toxicology

Risk =

Hazard X Exposure

Dose / Response

Individual Sensitivity

Effects of Amount on Response

Effects of Size on Response

Ethyl alcohol 10,000Salt (sodium chloride) 4,000Iron (Ferrous sulfate) 1,500Morphine 900Mothballs 500 (paradichlorobenzene)Aspirin 250DDT 250Cyanide 10Nicotine 1Tetrodotoxin (from fish) 0.01Dioxin (TCDD) 0.001Botulinum Toxin 0.00001Bee Venom ??

Agent LD-50 (mg/kg)

Descriptive Toxicology:

The science of toxicity testing to provide information for safetyevaluation and regulatory requirements.

The study of poisonsor

the adverse effects of chemical and physical agents on living organisms.

Toxicology Definitions

“The sensitivity of the individual differentiates a poison from a remedy. The fundamental principle of toxicology is the

individual’s response to a dose.”

S. G. Gilbert (1997)

An Individual View

Mechanistic Toxicology:

Identification and understanding cellular, biochemical andmolecular basis by which chemicals exert toxic effects.

Regulatory Toxicology:

Determination of risk based on descriptive and mechanistic studies, and developing safety regulations.

Clinical Toxicology:

Diagnosis and treatment of poisoning; evaluation of methods of detection and intoxication, mechanism of action in humans (human tox, pharmaceutical tox) and animals (veterinary tox). Integrates toxicology, clinical medicine, clinical biochemistry/pharmacology..

Occupational Toxicology:

Combines occupational medicine and occupational hygeine.

Environmental Toxicology: Integrates toxicology with sub-disciplines such as ecology, wildlife and aquatic biology, environmental chemistry.

 The scope of toxicity A.Mechanisms of Toxic Action

1. Biochemical toxicology

2. Behavioral toxicology-behavior is the final integrated expression of nervous function

3. Nutritional toxicology-the effects of diet

4. Carcinogenesis-cell growth

5. Teratogenesis-developmental process

6. Mutagenesis-genetic material

7. Organ toxicity-organ function

B. Measurement of toxicants and toxicity

1. Analytic toxicology

2. Toxicity testing

3. Toxicologic pathology

4. Structure-activity study

5. Biomathematics and statistics

6. Epidemiology

C. Applied Toxicology

1. Clinical toxicology

2. Veterinary toxicology

3. Forensic toxicology

4. Environmental toxicology

5. Industrial toxicology

 D. Chemical use classes

1. Agricuture chemicals

2. Clinical drugs

3. Drugs of abuse

4. Food additives

5. Industrial chemicals

6. Naturally occurring substances- phytotoxin, mycotoxin, inorganic minerals

7. Combustion products

 E. Regulatory Toxicology

1. Legal aspects-formulation of laws

and regulations and their enforcement

2. Risk assessment-

the definition of risks, potential risks

and risk- benefit equations

F. Development of antidotes

VSC/BMB497A 8

Xenobiotic

O

O

O

O O

OMe

Target OrganismCommunity/Population

Ecosystem

Absorption

Target Tissue

Target Cell

Exposure

Distribution

Metabolism

Classical

Toxicology

Xenobiotic

O

O

O

O O

OMe

MembraneTransport

OrganismToxicity

TissueToxicity

Reg

ulat

ory

Tox

icol

ogy

Excretion

Epidemiology/Environmental Toxicology

TargetMolecule

Cellular andMolecular Events

CellularToxicity

Mol

ecul

aran

d C

ellu

lar

Tox

icol

ogy

Genetic SusceptibilityBiomarkers

Risk assessment

Mechanismsand treatmentof toxicity

Risk characterization

Biology

Response

Metabolism

Toxic Effects

1. Immediate effect and delayed effect

CO, cyanide

2. Local effect and systemic effect

target organ

3. Reversible and irreversible effect

4. Anaphylactic reaction (allergic reaction)

5. Idiosyncratic reaction

Dose

Dose by definition is the amount of a substance administered at one time.

However, other parameters are needed to characterize the exposure to xenobiotics. 

The most important are the number of doses, frequency, and total time period of the treatment.For example:

650 mg Tylenol as a single dose

500 mg Penicillin every 8 hours for 10 days

10 mg DDT per day for 90 days

A common dose measurement is mg/kg body weight.

The commonly used time unit is one day and thus, the usual dosage unit is mg/kg/day.

Environmental exposure units are expressed as the amount of a xenobiotic in a unit of the media.

mg/liter (mg/l) for liquids

mg/gram (mg/g) for solids

mg/cubic meter (mg/m3) for air

Other commonly used dose units for substances in media are parts per million (ppm), parts per billion (ppb) and parts per trillion (ppt).

Fractionating a total dose usually decreases the probability that the total dose will cause toxicity.  The reason for this is that the body often can repair the effect of each subtoxic dose if sufficient time passes before receiving the next dose.  In such a case, the total dose, harmful if received all at once, is non-toxic when administered over a period of time.  For example, 30 mg of strychnine swallowed at one time could be fatal to an adult whereas 3 mg of strychnine swallowed each day for ten days would not be fatal.

vinyl chloride,

high dose-hepatotoxicant

long latent period at lower doses-carcinogen

very low dose-no effect

aspirin

chronic use-deleterious effects on the gastric mucosa, fatal dose 0.2-0.5 g/kg

metals

  dietary essentials eg. Iron, copper, magnesium, cobalt, manganese, and zinc

toxic at higher dose

"All substances are poisons; there is none which is not a poison. 

The right dose differentiates a poison and a remedy.“

Paracelsus (1493-1541)

Knowledge of the dose-response relationship:

establishes causality that the chemical has in fact induced the observed effects establishes the lowest dose where an induced effect occurs - the threshold effect determines the rate at which injury builds up - the slope for the dose response.

Dose Response

Individual, or graded, dose-response relationship

results from an alteration of a specific biochemical process

Quantal dose-response relationship

in a population-”all or none”

determination of the LD50

LD (lethal dose)50-the dose required to kill 50% of a population of an organism under stated conditions

Normal equivalent deviations(NEDs)NED for 50% response is 0NED for 84.1% response is 1Probit (probability unit)=NED+5

LD50 is used to:

A) classify substances or products for regulatory purposes including safe transportation and labeling,B) provide information for treatment of acute

intoxications C) standardize certain biological products,D) set dose levels for subsequent toxicity studiesE) provide comparative information on the

chemical's dose response curveF) provide data for evaluation and validation of

alternative test methods.

Classical LD50

The Classical LD50 test is used to determine the lethal dose (LD50) of a substance that will kill 50% of test animals.

Typically, this method can use 100 or more animals.

The test material is administered in increasing doses, usually 5 or more, to groups of 10 male and 10 female animals. Mortalities are recorded within a given period, and the LD50 is determined with the aid of statistical calculations.

2. Limit TestAcute toxicity test in which, if no ill-effects occur at a pre-selected maximum dose, no further testing at greater exposure levels is required.

Five to ten animals of each sex or 10 animals of the susceptible sex are administered a dose specified by regulations. Toxic responses occurring within a given period are recorded. Based on the results, a regulatory action or additional testing may be required.

The LD50 tests have become controversial among toxicologists, animal welfare organizations, legislators and the public primarily due to the ethics of using a large number of animals and evaluating only mortality.

CURRENT POLICIES

Food and Drug Administration: •Does not require the use of the Classical LD50 test. •Accepts alternatives. •Refers to the Limit test.

Organization for Economic Cooperation and Development:

•Discourages the use of Classical LD50 test. •Recommends the Limit test (2 g/kg dose). •When compound related mortality occurs in the limit test, then 5 animals per dose, at least 3 dose levels are used to produce a range of toxic effects and mortality rates; clinical observations and pathological investigations are conducted.

•A fixed dose procedure, which uses morbidity instead of mortality as the end point, is also recommended.

British Toxicology Society:

•The LD50 should only be determined with any accuracy where scientifically and ethically justified. Such cases are relatively rare.

•Examination of few animals in detail rather than many for statistical purposes.

•Limit tests could be used, provided animals in distress are killed humanely, if this would not interfere with the objectives.

•For classification of substances and preparations, a fixed-dose procedure targeted to acute signs could replace the current practice of LD50 determination.

Descriptive animal toxicity tests

Two main principle

1. The effects produced by a compound in

laboratory animals, when properly qualified,

are applicable to humans.

2. The exposure of experimental animals to

toxic agents in high dose is necessary and

valid method of discovering possible hazards

in human.

Descriptive animal toxicity tests

Acute Single dose with effects occurring for a short period of time (usually up to 96 hr)

Acute lethality (die in a 14-day period)

LD50 (Median Lethal Concentration)

Skin & eye irritation

sensitization

Subacute Multiple doses administered for up to 14 days

Subchronic Continuous dosing for up to 90 days

NOAEL-no observed adverse effect level

Chronic Continuous dosing for up to 6 months to 2 years

carcinogenic potential

• Acute effects do not predict chronic effects

• Doses causing chronic effects may not cause acute or sub-acute effects

• Chronic effects of a chemical exposure may manifest themselves as a common disease and go unnoticed

Course Objectives

Understand…….

• mechanisms by which chemicals cause cell injury and cell death

• the mode of action of specific organic and inorganic chemicals

• how to interpret results of in vitro tests for the evaluation of in vivo toxicity

• How multiple chemical exposures and other stressors can alter toxicity

• What factors influence individual susceptibility

• the importance of dose in determining adverse effects

of chemicals

• what factors influence the target organ dose of a chemical

• mechanisms by which chemicals affect specific organ system functions