Heroin physiological effects

Agonist drugs can also bind directly to the postsynaptic receptor, so mimicking the physiological effect of the neurotransmitter for example, morphine and heroin bind to the brain s opiate receptors and, thus, directly stimulate feelings of pleasure and pain... 

Fentanyl, a synthetic chemical compound, was discovered to be about 100 times as potent as morphine or heroin. Its chemical structure shown in Fig. 17.11 indicates that it can also be classified as an alkaloid. This compound has been widely used as an anesthetic in surgical procedures, as the physiological effects are much shorter-acting than morphine. And it gives a high like heroin, though short-lived. 

For many centuries morphine and codeine, alkaloids found in the oriental poppy plant, have been used as effective painkillers. Codeine, which is structurally similar to morphine, is used in some prescription painkillers and cough syrups. Heroin, obtained by a chemical modification of morphine, is strongly addicting and is not used medically. The structure of the prescription drug OxyContin (oxycodone) used to relieve severe pain is similar to heroin. Today, there are an increasing number of deaths from OxyContin abuse because its physiological effects are also similar to those of heroin. 

P-Endorphin. A peptide corresponding to the 31 C-terminal amino acids of P-LPH was first discovered in camel pituitary tissue (10). This substance is P-endorphin, which exerts a potent analgesic effect by binding to cell surface receptors in the central nervous system. The sequence of P-endorphin is well conserved across species for the first 25 N-terminal amino acids. Opiates derived from plant sources, eg, heroin, morphine, opium, etc, exert their actions by interacting with the P-endorphin receptor. On a molar basis, this peptide has approximately five times the potency of morphine. Both P-endorphin and ACTH ate cosecreted from the pituitary gland. Whereas the physiologic importance of P-endorphin release into the systemic circulation is not certain, this molecule clearly has been shown to be an important neurotransmitter within the central nervous system. Endorphin has been invaluable as a research tool, but has not been clinically useful due to the avadabihty of plant-derived opiates. 

Physiologically, cocaine is a powerful stimulant that quickens the heartbeat, but it wears off much faster than heroin, which works to depress the heart rate. The stimulant effect of the cocaine and the depressant effect of heroin wreak havoc on the heart, which can lose its rhythm. Cocaine frequently masks how much heroin has been consumed, and when the cocaine s effects dissipate, heart failure can result. John Belushi and River Pheonix both died this way after taking speedballs. 

Methadone is frequently used to treat heroin, codeine, hydrocodone, oxycodone, and morphine addictions. Methadone when used as prescribed, is safe and effective and does not cause euphoric sensations but does relieve physical withdrawal symptoms and reduces physiologic cravings. Methadone does have side effects which may be intolerable to some patients. They include constipation, water retention, drowsiness, skin rash, excessive sweating, and change in sex drive. Methadone has been used successfully in the treatment of opioid addiction for over 30 years. 

During heroin metabolism, the acetyl groups must be cleaved to yield morphine this might simply be hydrolysis or it may be an enzyme-mediated process. Codeine is also demethylated this is known to be an enzyme-mediated process (there are no simple chemical processes that would achieve this under physiological conditions), and some 10 %-15 % of the population are deficient in the enzyme, so codeine is not converted to morphine, and codeine has little analgesic effect for this group. Another 10 % of the population has overactivity of the enzyme, so that the codeine is demethylated very rapidly and effectively, and they must be careful not to consume an overdose, which would be less for them than for someone with more standard enzyme activity. Finally, in order to be excreted effectively in urine, the morphine is converted to a sugar derivative, to ensure water solubility. 

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