Drug Dependence And Addiction Biology Essay

Drug dependance occurs when a individual has physical and/or psychological demands for a peculiar drug. Physical dependance can ensue in symptoms of backdown when the individual stops taking the drug and the backdown symptoms finally differ on the type of drug. Psychological dependance consequences in the individual taking a drug because it gives pleasance and satisfaction, to bring around cravings and to avoid feelings of edginess ( Battegay et al.

1977 ) . Consequently, drugs that cause dependance autumn into two classs ; foremost, the psychomotor stimulations which cause an addition in excitement, encephalon activity stimulation and increased motive power and secondly, the CNS sedatives ; those drugs in which encephalon activity is depressed which finally consequences in sleepiness and desiccation ( Rang et al. 2007 ) . The most common legal drugs that are known to do dependance are ; intoxicant, nicotine and caffeine and the illegal drugs ; opiates, barbiturates, benzodiazepines, pep pills and cocaine. Due to drug dependance being a really large field, this essay will cover a few drugs in greater item and I have chosen to discourse opioids because most people that seek intervention sing drug usage are first and foremost, addicted to opioids ( WHO, 2010 ) . This essay will concentrate on the pharmacological facets ; of how the drug operates, activity dependant on construction, side-effects and pharmacokinetic belongingss ; the manner the drug influences its action.

We Will Write a Custom Essay Specifically
For You For Only $13.90/page!

order now

MAIN SectionDrug dependance is a status that normally causes obsessional behaviors and can ensue in pretermiting other demands, and finally, the despair for the ‘next hit ‘ overrides any concerns for safety. This can normally ensue in complications and unfavorable fortunes. A patient ‘s response to a drug is dependent on overall wellness and facets such as age, diet, gender, cardiovascular map, GI map and many other factors.

Tolerance to a drug occurs when larger doses are needed to bring forth the same consequence of that drug ; the patient normally has a reduced response to the drug with clip ( Berry et al. 2009 ) . Harmonizing to the World Health Organization, there are about 15.3 million people that suffer from drug dependance. Sing the usage of Opiates, the United Nations Office on Drugs and Crime exclaim at that place has been a world-wide elaboration of the production, transit and ingestion of this chemical, chiefly with respects to heroin. Internationally speech production, about 13.5 million people are said to take opioids and out of this bulk, 9.2 million are said to utilize diacetylmorphine.

Given that diacetylmorphine is used by the method of injection, wellness hazards like hepatitis and HIV are on the addition ( WHO, 2010 ) .Opioids are the household of opiates which involves the complete endogenous or man-made substances. Opiates are by and large used for non-synthetic opioids and it is an older term. Opioids are chiefly used to intend opioids and opiates. Consequently, the term opium is the infusion from the poppy, Papaver somniferum. Some opioids include morphia, diacetylmorphine ( diamorphine ) , codeine, pethidine and dolophine hydrochloride ( Rang, H.

P, et Al. 2007 ) . All opioids produce their consequence on the spinal cord and the limbic system, which is associated with emotion. Consequently, opioids are involved in doing effects on the tracts that send hurting from the peripheral nervous system to the cardinal nervous system. This essay will cover morphia, diamorphine, codeine and dolophine hydrochloride as these compounds are known to do the highest tolerance and dependance and they are the uppermost in analgetic authority ( Waller, et Al.

2010 ) . There are three chief types of opioids receptors ; the Mu ( Aµ ) type receptors, Kappa ( K ) type receptors and eventually, the Delta ( I? ) type receptors. The Mu ( Aµ ) type receptors are involved in the binding of morphia.


Mu ( Aµ ) type receptors

Kappa ( K ) type receptors

Delta ( I? ) type receptors






GI motility decreaseA-

A-Table – This tabular array shows the effects of the three major categories of the opioids receptors ( Adapted from Bennett & A ; Brown, 2003 ) .MorphineClinical usage of morphia is largely for terrible hurting, for illustration, in malignant neoplastic disease patients, patients enduring from a myocardial infarction and in terrible life endangering instances like route traffic accidents. It does non by and large cause dependance but nevertheless, if the ingestion is long term like in chronic instances, so dependance may happen ( Joint Formulary Committee, 2010 ) .

How morphia works

Morphine is the standard alkaloid that comes from opium. Morphine acts chiefly on the Mu ( Aµ1 ) type receptors which are located in the CNS ; consequently, the binding of morphia at these receptors gives pain alleviation and feelings of euphory ; nevertheless, peculiar marks of dependance are important in these type of receptors.

When morphine binds to the Mu ( Aµ2 ) type receptor, this causes respiratory depression and decreased motion of intestine content. Opioid peptide neurotransmitters in the CNS are endorphins, enkephalins and dynorphins. These endogenous opioid receptors attach to the three different types of receptors ( Bennett & A ; Brown, 2003 ) .

The opioid receptors, which are portion of the G protein-coupled receptors ( GPCRs ) household, inhibit adenylate cyclase which causes a decrease in the camp content ( Rang, et Al. 2007 ) . Consequently, opioids cause the K channels to open and suppress the voltage-gated Ca channel gap and this later causes a decrease in electrical irritability and suppression of substance P, which is involved in hurting neurotransmission ( Bennett & A ; Brown, 2003 ) .

Figure – When the agonist binds to the opioid receptor, which is portion of the GPCR household ; GTP activation occurs and adenylate cyclase is inhibited by the GTP-bound I± fractional monetary unit, which consequences in the decrease of camp concentration. Consequently, the I?/I? fractional monetary units cause the K channel activation and suppression of the electromotive force activated Ca channels. Note: GIRK stands for G protein-coupled inwardly-rectifying K channels ( Figure adapted from Kreek & A ; LaForge, 2007 ) .The unbalancing of the CNS chemical science occurs when the organic structure ‘s homeostasis is disrupted and the CNS strives to continue the normal position.

The CNS becomes disturbed and side effects arise ensuing in backdown symptoms. Morphine ingestion causes suppression of adenylate cyclase and this causes a lowering of the intracellular courier, cyclic adenosine monophosphate ( camp ) as shown in figure 1. Homeostasis compensation so tries to increase the camp synthesis but this causes adenylate cyclase production. When the individual stops taking morphia, there is a larger sum of camp produced and this continues until the adenylate cyclase degrees return to the normal criterion. Regular opioid usage causes adenylate cyclase to be amplified and consequently, the high degrees of camp production cause the backdown effects ( Rang, H.P, et Al.

2007 ) .Figure 2- This figure shows that after morphia is consumed, adenylate cyclase is in inhibited which later causes camp production to be reduced. The high degrees of camp production cause backdown symptoms and this lasts until the adenylate cyclase look goes down to a normal degree. When adenylate cyclase rises, camp production lessenings when morphia is consumed and this is a peculiar cause of tolerance. ( Figure adapted from Rang, H.P, et Al.

2007 ) .When backdown takes topographic point, adenosine ; which is involved as adenosine triphosphate ( ATP ) used in energy transportation and besides a important go-between of the cardinal nervous system is of import in drug dependance. The synthesis of adenosine is amplified when a individual goes through drug backdown and this is because camp, which, is obtained from ATP every bit good, is produced in surplus during backdown and is converted to adenosine.

Subsequently, adenosine Acts of the Apostless on the A1 receptors at the presynaptic nervus terminus and it accordingly inhibits the release of the excitant neurotransmitter ; glutamate, in the nervous system. This suppression of glutamate release consequences in the beginning of neural hyperexcitability. There are ongoing trials that may assist people enduring from drug maltreatment ; by the usage of adenosine agonists as these would assist forestall drug backdown symptoms ( Rang, H.P, et Al. 2007 ) .CNS effectsPain alleviation, feelings of euphory, sedation effects, respiratory depression, hypotension, bottleneck of students, sickness.Peripheral effectsContraction of smooth musculus, decrease of intestine motility, scabies, urine keeping.Table – This tabular array shows the effects of morphia when it binds to the Mu ( Aµ1 ) receptors, which are located in the CNS and Mu ( Aµ2 ) receptors which are located in the peripheral tissues ( Reid, et Al.

2006 ) .


The construction consists of a phenanthrene skeleton that has two aliphatic rings, which are made up of C and H, it besides has two planar rings and its structural expression is C17H19NO3 and has a molecular mass of 285.34g. Other parallels of the morphia construction have different groups at the hydroxyl groups on place 3 and 6 in figure 2 or at the nitrogen portion of the molecule on place 17 ( Rang, H.P, et Al. 2007 ) . The man-made opioids have alternate functional groups at places 3, 6 and 17 ; these may be esters, hydroxyl groups, ketones, methyl groups or excess C atoms ( Armstrong & A ; Cozza, 2003 ) .


Position 3Position 6Position 17AlkeneAmine groupAromatic ringAlcohol groupEther groupPhenol groupFigure 3 -the construction of morphia ; exposing the phenol group, ether group, intoxicant group, aromatic ring, amine group and the olefine. ( Diagram adapted from: Nelson, 2008 ) .


Side-effects normally experienced with morphine ingestion are respiratory depression ; which causes a reduced sensitiveness to carbon dioxide and this is the premier cause of decease in patients who over dosage. Morphine ingestion can do an addition in pCO2 when morphia disposal is a bit high ; oxygen impregnation lessenings and on occasion consequences in hypoxia. Miosis, Nausea and emesis and irregularity are other considered side effects.

Constipation occurs due to a lessening in the GI motility. Histamine release is another side consequence and therefore morphia is non recommended for people that suffer with asthma. Withdrawal and dependance symptoms are non as widespread in morphia as they are in diamorphine ( Dale & A ; Haylett, 2009 ) .

Pharmacokinetic Properties

When morphia is taken orally, it is metabolized when it passes from the intestine wall to the liver and it is said that 20 % of a individual dosage goes to the system circulation ; this is known as the first-pass consequence in which the concentration of morphia is much less when it gets to the system circulation. In minutes of circulatory daze like in route traffic accidents, morphia is given intravenously because hypodermic and intramuscular injections would take excessively long to be absorbed ( Bennett & A ; Brown, 2003 ) .Subsequently, morphia is metabolized by two variety meats ; the liver and the kidney. It is metabolized to morphine-6-glucuronide and morphine-3-glucuronide which are secreted in the piss.

A survey undertaken on morphine-6-glucuronide shows that is has pain relief effects ; nevertheless larger sums of morphine-6-glucuronide are needed to give the same result as morphia ( Skarke C, et Al. 2002 ) . The half life of morphia is between 3-4 hours ( Rang, et Al. 2007 ) .

Diamorphine ( besides known as 3,6-diacetylmorphine and diacetylmorphine )Diamorphine is a man-made drug processed from morphia. It is used in medical specialty for ague and chronic hurting. Subsequently, is more effectual than morphia with respects to trouble alleviation, due to its solubility.

It is a really common drug that causes dependance and for this ground it is banned for medical usage in most states ( Bennett & A ; Brown, 2003 ) .

How diamorphine works

Diamorphine is a narcotic anodyne, which is known to hold rather a strong dependance liability. Bing an parallel of morphia, this substance is similar in construction to morphine and Acts of the Apostless by comparable mechanisms. Heroin is the diacetate ester of morphia and later, it is more lipotropic and crosses the blood-brain barrier easier due to the ethanoyl group groups. This causes major addition in euphory and addictiveness ( Rang, et Al. 2007 ) .

Heroin itself does non hold strong CNS effects, which is due to a low affinity binding to the opioid receptors. ( Rossi et al.1996 ) . However, diamorphine goes through an intermediate procedure during metamorphosis, as shown in figure 3, to bring forth a compound called 6-acetylmorphine and this metabolite has a much greater affinity for the Mu ( Aµ ) type receptors and is able to traverse the blood encephalon barrier where it is subsequently metabolized to morphine when it is penetrated into the CNS ( Weitz et al. 1988 ) .

Heroin is normally injected but it is besides snorted and inhaled by smoking. The method of injection causes the greatest feeling of euphory ; accordingly, euphory tends to take much longer when diacetylmorphine is injected into the musculus or by snorting and smoking usually takes 15 proceedingss before these feelings occur. Following to the euphoric emotions, sleepiness starts to take topographic point and normally mental map is dulled and this is because the usage of opioids causes depression of the CNS. When mental map is dulled, this causes reaction clip to diminish every bit good as cardiac end product and respiration have a decreased consequence. With drawn-out diacetylmorphine usage, the organic structure becomes accustomed to holding this drug in its system and larger doses are required to give the euphoric feelings ; consequently, larger doses normally cause over dosage. Withdrawal effects arise when diacetylmorphine depletes in the system taking to the side effects ( Stenter & A ; Mathieson, 2007 ) .


Figure 4- Diamorphine undergoes a rapid metabolization procedure ( Diagram adapted from Barret et Al. 1991 ) .Diamorphine is deacetylated really quickly to 6-acetylmorphine which is less lipid soluble than its precursor and consequently, crosses the blood-brain barrier at a slower rate. Nevertheless, 6-acetylmorphine has a greater affinity to the opioids receptors situated in the encephalon ( Morrison et al. 1991 ) .

Morphine is metabolized to morphine-6-glucuronide, morphine-3-glucuronide and normorphine as shown in figure 3, which is another metabolite of morphia ; they are all secreted in the piss.


Side effects of diamorphine are similar to morphine ; giddiness, itchiness, sweat, sickness and emesis, irregularity, sleepiness, lessening in watchfulness, meiosis and in high doses respiratory depression is apt to happen ( Smith & A ; Beecher 1961 ) .

Pharmacokinetic Properties

Diamorphine has a 2-3 minute half life is uncommonly detected in the blood due to its rapid transition to 6-acetylmorphine ( Rang, et Al. 2007 ) . The backdown symptoms begin after 6-12 hours. Consequently, the peculiar backdown symptoms experienced consist of feelings of anxiousness, insomnia ; runny nose, sweat, febrility, diarrhea, back and musculus hurting, musculus cramps, dilation of the student and goose bumps ( Stenter & A ; Mathieson, 2007 ) .

Codeine ( 3-methylmorphine )

How Codeine works

Codeine is another morphia parallel that has high affinity for the Mu ( Aµ ) type receptors and a well lower affinity to the Kappa ( K ) type receptors and the Delta ( I? ) type receptors. Codeine is less powerful than morphia and is usually taken orally because it has a good soaking up. It is rather normally combined with isobutylphenyl propionic acid, paracetamol and acetylsalicylic acid.

This drug is utile in mild/moderate hurting like concerns, back hurting etc. and dependance does happen on occasion but it is non every bit common as morphia and diamorphine. It has some antitussive activity and is often used as a suppressant in cough medicine, like codeine linctus ( Reid, et Al. 2006 ) .

Peoples who are by and large dependent on codeine have outside jobs like depression or anxiousness upsets. Codeine is of popular usage in chronic hurting sick persons and the ground people could go dependent is if their hurting intervention is non assisting to handle their hurting efficaciously ( Sproule, et Al. 1999 ) .


Codeine has a methyl group on place 3 of the hydroxyl group on the morphia construction.

It is changed from -OH to -OCH3, as in figure 5 ( Armstrong & A ; Cozza, 2003 ) .Extra methyl groupPosition 3Figure 5- The construction of codeine with the excess methyl group on place 3 ( Figure adapated from National Center for Biotechnology Information, 2010 ) .


Long term usage of codeine can do irregularity ( Bennett & A ; Brown 2003 ) and it chiefly has similar side effects to the other two opioids mentioned above.

Pharmacokinetic Properties

Codeine is metabolised to morphine and the glucuronides by the CYP3A4 and CYP2D6 enzymes ( Nagar & A ; Raffa, 2008 ) and undergoes first base on balls metamorphosis ; consequently, 10 % is demethylated to organize morphia. The half life of codeine is between 3-4 hours ( Bennett & A ; Brown 2003 ) .

Codeine is metabolized by the enzyme CYP3A4 to norcodeine and is besides glucuroridated to codeine-6-glucuronide in the liver. In add-on, codeine is besides metabolized to morphine by the enzyme CYP2D6 and the metamorphosis of morphia occurs, where it is glucuronidated to morphine-3-glucuronide and morphine-6-glucuronide which is involved in the result of hurting alleviation and the kidney is in charge of the glucuronide remotion as shown in figure 6. However, accretion of the glucuronides, possibly in an over dosage, could hold desperate effects on the kidney ( Nagar & A ; Raffa 2008 ) .Figure 6- Diagram demoing the metamorphosis of codeine in the liver by the enzymes CYP3A4 and CYP2D6. The glucuronides are excreted by the kidney ( Adapted from Nagar & A ; Raffa 2008 ) .DecisionOpioids are really normally used to handle different types of ague and chronic hurting.

The production of metabolites from each drug has great importance in the drug efficaciousness and tolerability in patients. To avoid opioid dependance, drugs that do non hold active metabolites may be prescribed for ague and chronic hurting instances ( Nagar & A ; Raffa 2008 ) . Lots of drugs can do dependance ; nevertheless, the household of opioids were explored, three of the drugs were discussed ; morphia, diamorphine and codeine, this enabled the similarities, differences and the root of drug dependence on a pharmacological footing to be displayed ; accordingly, when the organic structure ‘s homeostasis is imbalanced, the CNS attempts to change the organic structure back to a normal degree. In drug dependance, backdown is common and by utilizing adenosine agonists, these can assist with the backdown symptoms ; consequently, more research is being undertaken to assist those enduring from drug maltreatment ( Rang, H.P, et Al.

2007 ) .


I'm Ruth!

Would you like to get a custom essay? How about receiving a customized one?

Check it out