Tobacco (tambakhu) is used throughout the world for smoking in cigarettes, cigar, pipes etc and is also chewed either alone or mixed with lime. It is prepared from cured leaves of Nicotina tabacum. It contains an alkaloid Nicotine which is one of the most deadly cardiac poisons. Tobacco dry leaves contain from 0.6 to 6 % of nicotine. Nicotine is colorless, volatile, bitter and hygroscopic liquid. It is soluble in water and alcohol. Only 3 to 4 drops of pure poison if taken internally may prove fatal.
Nicotine is a stimulant of the central nervous system, and is abused widely all over the world in the form of inhalation (cigarette, cigar, pipe, beedi), nasal insufflation (snuff), or chewing. Person consuming excess of tobacco for a long period may suffer from chronic poisoning.
The chemical formula of nicotine is C10H14N2.
- It is present in Smoking tobacco.
- It is used by Chewing and Snuff.
- It is also used as Insecticide.
- In adult, the lethal dose is 40 to 60 mg of nicotine
- 15 to 30 gm of crude tobacco if taken orally.
- Cigarette contains about 10–20 mg of nicotine but by smoking only 1–2 mg is taken inside.
Fatal period of nicotine is 5 to 15 minutes.
Absorption, metabolism and excretion
● Tobacco or nicotine is absorbed from skin, mucous membrane and lungs.
● It is metabolized in liver and excreted in urine.
● Small amounts are also excreted in Breast milk. Nicotine levels in breast milk are maximum immediately after a woman smokes a cigarette, and nicotine levels in breast milk begin to decrease over the next two hours. According to several sources, the half-life of nicotine in breast milk is 95 minutes.
Mechanism of Action
► Nicotine acts on nicotine receptors present in autonomic ganglia, adrenal medulla, central nervous system, spinal cord, neuromuscular junction and chemoreceptors of carotid and aortic bodies. It binds stereo-specifically to select acetylcholine receptors (nicotine receptors).
► In the CNS, the highest concentration of nicotine receptors is found in the limbic system, midbrain, and brainstem.
► At moderate doses, nicotine stimulates the reticular activating system producing an alerting pattern on the EEG, with resultant favourable effects on memory and attention. But higher doses cause tremor and convulsions due to a CNS disinhibition mechanism.
► Nicotine stimulation of vagal centres in the medulla induces nausea and vomiting, while the gastro-oesophagal reflux is provoked due to a lowering of sphincter pressure and increased acid secretion. Larger doses cause diarrhoea due to both central and parasympathetic excitation.
► By acting directly on nicotine receptors in endocrine glands, as well as by stimulating neurohumoral pathways in the CNS, nicotine enhances release of catecholamines, vasopressin or antidiuretic hormone, growth hormone, ACTH, cortisol, prolactin, serotonin, and beta endorphins. Nicotine also increases amylase, trypsin and chymotrypsin activity.
► Nicotine also suppresses appetite and also resulting in weight loss.
Sign and symptoms
Early Effects (15min to 1 hour)
- Pain in abdomen
- Tachycardia followed by bradycardia.
- Blurred vision
- Muscle fasciculations
- Constricted and dilated pupils
Delayed Effects (after 1 hour)
- Also known as nicotine addiction.
- Common among smokers, tobacco chewers.
- Develops physical dependence, manifested by recurrent craving for tobacco, tolerance, cough, impaired memory and amblyopia.
- Tobacco withdrawal is manifested by change in mood, insomnia, restlessness, constipation, headache and anxiety.
- Lung cancer
- Respiratory diseases: Emphysema, bronchitis, asthma, pneumonia.
- Obstetric and neonatal conditions: Abortion, abruptio placenta, placenta praevia, preterm labour, pre-eclampsia, growth retardation, congenital malformations, sudden infant death syndrome, foetal or neonatal death.
- Peptic ulcer
- Alzheimer’s disease.
- Decontamination by stomach wash.
- Emesis is contraindicated.
- Gastric lavage with Activated charcoal is effective and must be administered in the usual manner.
- In cases of dermal exposure (e.g. wet tobacco leaves, spillage of nicotine liquid), clothing should be removed, and skin thoroughly washed.
- Symptomatic and supportive measures.
- Benzodiazepines for convulsions are suggested.
- Atropines for bradycardia are suggested.
- IV fluids and vasopressors (dopamine or noradrenaline) for hypotension are suggested.
- Respiratory compromise is managed by oxygen, intubation, and positive pressure ventilation.
- Nicotine replacement therapy.
Physiological Effects of Nicotine
- CNS stimulation, with improvement of attention and memory.
- Relief of anxiety
- Reduced hunger and body weight
- Increased metabolic rate
- Increased levels of catecholamines, vasopressin, growth hormone, ACTH, cortisol, prolactin and betaendorphin.
- Lipolysis, increased free fatty acids.
- Increased heart rate, cardiac output and blood pressure.
- Cutaneous and coronary vasoconstriction.
- Relaxation of skeletal muscles.
Post mortem findings
- Brownish stains may present over skin.
- Brownish froth at mouth and nostrils.
- Signs of asphyxia.
- Tobacco smell may present.
- Brownish discoloration of esophagus and gastric mucosa.
- Stomach may contain fragments of tobacco leaves.
- Pulmonary edema.
Test for detection of Nicotine
► Acute poisoning can be confirmed by estimating plasma nicotine level.
► High pressure liquid chromatography is generally utilised to assay nicotine levels. Plasma level greater than 40 to 50 ng/ml indicates serious toxicity.
► Polymorphonuclear leucocytosis and glycosuria are often encountered in nicotine overdose.
► Passive tobacco smoke exposure is usually determined by estimating cotinine levels in plasma, urine, or saliva.
► Fagerström Test for Nicotine Dependence.
Medico legal aspects
- Accidental poisoning may occur due to overdose.
- Specially, among children may be seen as they may ingest cigarette or tobacco leaves by mistake.
- Sometimes, they may also suffer after drinking hookah water which contains high concentration of nicotine.
- Suicidal and homicidal poisonings are rare but have been reported.
- suicidal ingestion of nicotine pesticides used to be reported occasionally.
- Tobacco is also used for infanticide or to procure criminal abortion.
- Occupational hazard.
- Malingering to induce illness
- Putrefaction has no effect on nicotine. So, nicotine can be detected even after death for a long time.
- Dr. K.S. Narayan Reddy. The essential of forensic medicine and toxicology.34th edition.
- VV Pillay. Modern medical toxicology.4th edition.
- R.K.Sharma. Concise textbook of forensic medicine and toxicology. 3rd edition.