Stimulant: Caffeine

 Stimulants are psychoactive drugs that induce temporary improvement in either mental or physical functions or both. stimulants are also reffered to as "uppers". Caffeine is a central nervous system stimulant of the methylxanthine class. It is the most widely consumed psychoactive drug in the world. it is legal and unregulated in nearly all partss of the world so its is prone to abuse. Caffeine is chemically realated to the adenosine and guanine bases of DNA and RNA. Its major source is coffee. beverages containing caffeine are taken to prevent drowsiness and boost performance. taking caffeine with alcohol reduces the potency of caffeine but alcohol effects remain the same.

Uses
- Treatment and prevention of bronchopulmonary dysplasiain premature infants.
- Treatment of apnea of prematurity.
- Treatment of orthostatic hypotension
- Treatment and prevention of drowsiness

Side Effects

Positive effects
- Increased attention and alertness, decreased fatigue.
- Lower risk of cardiovascular disease
- Lower risk of diabetes
- Lower risk of cancer
- Increased metabolic rate
Negative effects
- Anxiety
- Increased vasoconstriction and blood pressure
- Reduced control of fine motor movement
- Stimulation of urination
- Increased sleep latency

Overdose
Symptoms of caffeine overdose or intoxication includes restlessness, anxiety, insomnia, increased urination, muscle twitching, rapid heart beat, psychomotor agitation.
In cases of larger overdoses, depression, disorientation, disinhibition, delusions, hallucinations, psychosis etc.
Massive overdoses may result in death.

Mechanism Of Action
There are many proposed mechanism of action to explain the effect of caffeine. the most prominent mechanism is inhibition of cell surface receptors for adenosine and this consequently prevenys the onset of drowsiness induced by adenosine.

Pharmacodynamics
Caffeine has effects on the central nervous system, kidney, and cardiac and skeletal muscle as well as smooth muscle.
- Central Nervous System Effects
In low and moderate doses, caffeine cause mild cortical arousal with increased alertness and deferral of fatigue. The caffeine contained in beverages—eg, 100 mg in a cup of coffee—is sufficient to cause nervousness and insomnia in sensitive individuals and slight bronchodilation in patients with asthma. The larger doses necessary for more effective bronchodilation commonly cause nervousness and
tremor in some patients. Very high doses, from accidental or suicidal overdose, cause medullary stimulation and convulsions and may lead to death.\
- Effects on Kidney
Caffeine is a weak diuretics. This effect may involve both increased glomerular filtration and reduced tubular sodium reabsorption. The diuresis is not of sufficient magnitude to be therapeutically useful.
- Effects on Smooth Muscle
The bronchodilation produced by caffeine is the major therapeutic action in asthma. Tolerance does not develop, but adverse effects, especially in the central nervous system, may limit the dose. In addition to their effect on airway smooth muscle, these agents—in sufficient concentration—inhibit antigen-induced release of histamine from lung tissue; their effect on mucociliary transport is unknown.
- Effects on Skeletal Muscle
The respiratory actions of caffeine may not be confined to the airways, for they also strengthen the contractions of isolated skeletal muscle in vitro and improve contractility and reverse fatigue of the diaphragm in patients with COPD. This effect on diaphragmatic performance—rather than an effect on the respiratory center—may account for theophylline・s ability to improve the ventilatory response to hypoxia and to diminish dyspnea even in patients with irreversible airflow obstruction.

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