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Effects of Medical Marijuana on The Brain System

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Marijuana is a hemp plant called Cannabis sativa It is available in the forms of dried leaves, flowers, stems, and seeds. The resinous concentrate obtained from the plant is known as Hash Oil (NIH).  Marijuana is an annual crop plant. It grows from seeds in open areas exposed to sunlight. It germinates within a week and attains its full growth in 4 to 8 months (Rajasekar). Marijuana contains medicinally active compounds that act on the brain. The main active compound is delta-9-tetrahydrocannabinol (THC).  THC related compounds (cannabinoids) are also medicinally active (NIH). These compounds are called cannabinoids. The THC content varies according to the source of cannabis and its preparation (Ashton).

Nonmedicinal effect of marijuana is the intoxication it can produce. Marijuana is rolled as cigarettes and smoked. The odor of the smoke is distinct, pungent, and sweet-and-sour. Marijuana is consumed along with food and its decoction is served as tea. All variants of marijuana produce initial excitement followed by depression (NIH).

Effects of Medical Marijuana on The Brain System

Marijuana is used in ayurveda for its medicinal properties. Its derivatives act as analgesic, anti-inflammatory, hallucinogenic, and sedative. Marijuana is recommended in cancer chemotherapy as an antiemetic and for treating glaucoma. Marijuana plant in ayurveda is used for its hallucinogenic, hypnotic, sedative, analgesic, and anti-inflammatory properties.  (Rajasekar).

Medical marijuana or medical cannabis is available as leaves and flowering tops. Medical marijuana is a schedule I drug. Derivatives of cannabis or marijuana are in use for their medicinal actions in United States and Canada for a long time. Such derivatives are dronabinol and nabilone that are schedule III and schedule II drugs respectively. Another derivative ‘nabiximol’ has not been approved by the USFDA (Borgelt, Franson and Nussbaum).  The nature of formulation and patient’s character influence the pharmacological actions of cannabinoid compounds. The cannabinoid receptors CB1 and CB2 respond differently. The cannabinoid delta-9-tetrahydrocannabinol exerts primary psychoactive actions. Cannabinoid derivatives dronabinol and nabilone are used for treating nausea and vomiting during cancer chemotherapy. It is also given to patients suffering from anorexia due to acquired immune deficiency syndrome. Cannabis compounds are recommended for treating pain and muscle spasms (Borgelt, Franson and Nussbaum).

More than 400 compounds are present in herbal cannabis. The plant genus cannabis contains more than 60 compounds that are aryl-substituted meroterpenes called cannabinoids. The cannabinoids have potential psycho-activity. Tetrahydrocannabinol (THC) is the active cannabinoid. Other forms of cannabinoids have additive, synergistic or antagonistic action similar to THC (Ashton).

Pharmacokinetics

On smoking marijuana, THC is absorbed into the bloodstream through the lungs. THC is carried to the brain and other organs of the body through the bloodstream. But the absorption of THC is slow when taken along with food or drink (NIH). When herbal cannabis is inhaled as smoke, approximately 50% of the Tetrahydrocannabinol is absorbed into the blood stream through the lungs immediately. The effect of its action is felt within minutes. When consumed orally, the bioavailability in the blood is approximately 25-30% only. This is due to the slow absorption through the gastrointestinal route. THC is partly metabolized in the liver.  Its actions are delayed and prolonged (Ashton). Cannabinoids are highly lipid soluble. After absorption, cannabinoids get distributed to all the body tissues including the brain. After accumulating in fatty tissues, peak concentration is attained in 4-5 days. The half-life of THC elimination of single dose from tissues is about 7 days and complete elimination takes up to 30 days. In the brain, it is differentially distributed and concentrated in neocortical, limbic, sensory, and motor regions. The rapid absorption within minutes and slow absorption for days together indicate their affinity towards fat containing tissues and plasma (Ashton). Cannabinoids get metabolized in the liver. All metabolites are psychoactive having half-lives for prolonged days. Twenty five percent of metabolites are excreted partly in urine. 65% get reabsorbed from the gut. This sequence is responsible for intoxication by cannabinoids (Ashton).

Pharmacodynamics

The effect of cannabinoids takes place on interaction with its receptors. Such receptors are called CB1 receptors and CB2 receptors. The CB1 receptors are present in human brains and peripheral nerves and the CB2 receptors are present in spleen and immune cells (Ashton). Delta-9-tetrahydrocannabinol (THC) constituent of marijuana increases heart rate, slightly increases supine blood pressure, and on occasion produces marked orthostatic hypotension. Marijuana smoking by the people with cardiovascular disease poses health risks due to increased cardiac work, increased catecholamine levels, carboxyhemoglobin, and postural hypotension (Jones). Regular smoking of marijuana leads to bronchitis and emphysema. The constituents of smoke are nicotine, carbon monoxide, irritants, tumor causing chemicals, and carcinogens. Oropharyngeal cancer is prevalent among young people who smoke marijuana regularly (Ashton).

Effect on The Brain

When the THC enters the brain, it stimulates brain’s reward system leading to euphoric feelings with heightened sensory perception. It stimulates the brain cells to release the dopamine (NIDA). The THC acts on cannabinoid receptors in the body cells. The Brain contains highest concentration of cannabinoids receptors. Chemicals similar to the THC are present in the human body and in the neural communication network called the endocannabinoid system. The THC overactivates the endocannabinoid system that is responsible for normal development of brain and its function. The brain part responsible for influencing sensory perceptions gets activated by the THC that alters the normal functions of the brain (NIH). Marijuana affects the brain development in young people sometimes causing damage on thinking, learning and memory. Deficiency in cognitive abilities is not restored fully even after quitting smoking marijuana (NIH). Marijuana consumption affects the daily life and worsens the existing problems. Heavy users show lack of life satisfaction and poorer state of mental and physical status. Their academic and career successes are also affected.  Productivity suffers heavily due to absenteeism, sluggishness, and accident (NIH).

Hallucination and fear are the psychotic reactions exhibited in high dose marijuana usage. It aggravates the symptoms of illness in patients with schizophrenia. Marijuana use leads to development of psychosis at a later stage. The genetic variables, amount of drug used, drug potency, and age influence the psychotic reaction. Young people are at increased risk for problems at later age. Mental health problem among adult users include anxiety, depression, suicidal thoughts, and lack of willingness to get engaged in normal activities. Marijuana consumption during pregnancy affects the brain of the fetus. Children develop symptoms of attention deficit, poor memory, and problem solving abilities. Risk of injury and death are associated with its use while driving vehicle as marijuana impairs judgment and motor coordination (NIH).

Addiction

Disorder due to the illicit use of the drug marijuana is widespread. Marijuana is commonly used by the young people and adults causing much damage to their health. Marijuana alters the physical and mental status. The emotional and behavioral changes take place affecting the normal life (Nixon). Marijuana addiction takes place in three stages: 1) obsession while acquiring marijuana, 2) habitual use of marijuana and 3) relapse due to frequent use of marijuana. The abnormal use of marijuana leads to many disorders.  Acute and chronic use of marijuana affects medical, psychiatric, neurological, traumatic and sociological consequences. Main course of addiction should be identified. The addiction or dependence is diagnosed as the etiological or precipitating factor to prevent and treat these conditions (Miller and Gold).

Abstinence of marijuana usage: Long-term marijuana users trying to quit, show the symptoms that make them difficult to abstain. Withdrawal syndrome takes place following the restriction on the daily use of marijuana. The main symptom is negative mood characterized by irritability, anxiety, sleeplessness, and misery that lead to craving. These symptoms are associated with muscle pain, chills, and reduced food intake due to loss of appetite (Haney, Hart and Vosburg),  (NIH).

Cognitive-behavioral treatment and motivation are the interventions to control marijuana addiction. No standard medications are available at present. But medications are available to lessen the withdrawal symptoms, block intoxication, and prevent relapse (NIH). These symptoms are relieved on administering the oral THC. Alternatively, divalproex (combination of sodium valproate and valproic acid) administration reduces craving.  However, it increases the irritability and other symptoms. It has been found that divalprox affects badly the mood and cognitive behavior (Haney, Hart and Vosburg).

Several medications have been tried clinically for treating marijuana users. Medications tried are grouped into three categories: 1) using drugs that are effective in other disorders 2) using drugs that are known to reduce the cannabis withdrawal symptoms and 3) using drugs that act directly on cannabinoid receptors. Controlled laboratory and clinical studies have shown that several drugs have proven therapeutic actions for treating marijuana addiction problems.  Such drugs are buspirone, dronabinol, fluoxetine, lithium, lofexetine and rimonabant. These are known as antidepressant drugs (Vandrey and Haney).

Conclusion

Thus, Marijuana has medical uses as well as negative intoxicating and psychotropic effects. Marijuana’s abuse results in psychomotor impairment that carries high risk of road, rail and air traffic accidents. Chronic use ends up with dependence, withdrawal symptoms and cognitive impairment. The continued usage of marijuana causes respiratory, cardiovascular and other health problems. In spite of the ill effects of marijuana’s abuse and addiction, the derivatives of marijuana have shown promising results and potency to treat many diseases and disorders.

Works Cited
  • Ashton, C.Heather. “Pharmacology and effects of cannabis: a brief review.” The British Journal of Psychiatry 178, 101-106. 2001. Web 19 May 2014
  • Borgelt, LM, et al. “The pharmacologic and clinical effects of medical cannabis.” Pharmacotherapy 33.2  195-209, 2013. Web 19 May 2014
  • Haney, M, et al. “Marijuana withdrawal in humans: effects of oral THC or divalproex.” Neuropsychopharmacology 29.1  158-70, 2004. Web 19 May 2014
  • Jones, RT. “Cardiovascular system effects of marijuana.” J Clin Pharmacol 42.11 suppl  58-63. 2002. Web 19 May 2014
  • Miller, NS and MS Gold. “The diagnosis of marijuana (cannabis) dependence.” J Subst Abuse Treat 6.3, 183-92. 1989. Web 19 May 2014
  • NIDA. “How does marijuana use affect your brain and body?” 2012. National Institute on Drug Abuse. 2012. Web. 19 May 2014
  • NIH. “DrugFacts: Marijuana.”  National Institute of Drug Abuse (2014) . Web. 19 May 2014
  • Rajasekar, Saha. “Marijuana (Cannabis): Its Illusion And Information.” International Journal of Pharma and Bio Sciences 3.1  190-200. 2012. Web 19 May 2014
  • Vandrey, Ryan and Margaret Haney. “Pharmacotherapy for Cannabis Dependence: How Close Are We?” CNS Drugs 23.7, 543-553. 2009. Web 19 May 2014

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