The Chemistry of Morphine

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Introduction

Morphine (C17H19NO3) is the active therapeutic agent that is derived from the opium poppy. It acts as a powerful opioid analgesic remedy and as a psychoactive drug that acts directly on the central nervous system to relieve the pain and symptoms related to most mental problems (LeCounter par.1).

The natural source of morphine and the history of its use

The main natural source of opium is the terrestrial plant, Opium Poppy (papaver somniferum). Opium then acts as the source of most opiates such as Morphine (Ebadi 446). The ancient pioneers of Alchemy are said to have employed an opium-based elixir in their studies as an active pain killer. At around 1522, an alchemist known as Paracelsus recommended the use of this formulation as a painkiller. Upon the advent of trade-in opium-based products by Indians in the 18^th century, many physicians and patients adapted the use of another opiate known as Laudanum. The discovery of Morphine dates back to 1804 when a German scientist, Friedrich Serturner, extracted the alkaloid from its natural source. It was introduced into the market around 1817 by the scientist and his company. It was meant for use as an analgesic for patients suffering from opium and alcohol addiction. Another active form of the drug, heroin was synthesized in 1874 and introduced to the public in 1898 by Bayer. Heroin is said to be 1-2 times more potent than its parent drug, morphine. Morphine had become the most abused drug in the world until the production of heroin (Maisto 37). This forced the US government to label it as a controlled substance in 1914. The analgesic strength of the two drugs was undisputed for quite a long time until other classes of opioids began to be synthesized by the late 20^th Century. To date, morphine is still prescribed for opium addiction in case heroin is in short supply (Maisto 228).

Production of Morphine

Morphine was first extracted from the poppy straw by Janos Kabay, a Hungarian chemist. The method involves the extraction of the alkaloids from their combination with the Meconic acid in the opium poppy. This can be achieved through the use of a strong acid such as Sulphuric acid but care should be taken in that the acid chosen does not react with the alkaloids. The crushing plant is mixed with the acid and the extraction is carried out 6-10 times to ensure that all the alkaloids are extracted into the solution. The alkaloids are then extracted from the resultant solution using Ammonium Hydroxide (NH4OH). Finally, morphine should be separated and purified from the mixture of opium alkaloids. The last step is easily achieved because the other alkaloids occur in low concentrations as opposed to morphine which represents about 8-19% of the dry weight of the crushing plant (Ebadi 471).

Uses and Side Effects of Morphine

Morphine’s ability to directly act on the central nervous system makes it a preferred intervention in painkilling. It is capable of directly acting on synapses. Therefore, morphine is indicated for different forms of pain during myocardial infarction, sickle cell crisis, surgical operations (used both for pre-and post-operative pain relief), trauma, and back pain. It is also indicated for relieving chronic pain and pain associated with kidney stones. Morphine has also been employed as an appendage for anesthesia and palliative care. During chronic conditions of diarrhea, morphine is employed as an anti-diarrheal remedy. It has also found therapeutic use in diabetes in lowering and stabilizing the glucose levels besides alleviating other diabetic effects such as neuropathy (Maisto 232).

Reduced gut mobility that sanctions constipation is caused by the action of morphine on the myenteric plexus. It exerts its effect through its receptors in the stomach thereby inhibiting gastric emptying and peristalsis in the intestines. Consequently, the rate at which food enters and leaves the digestive system is greatly reduced. Morphine can also act on the stomach directly thereby inhibiting the rate of NO production (Maisto 243).

Addicts of morphine suffer from extreme feelings of euphoria, ambitions, relaxation, nervousness, drowsiness, and sleeplessness. Morphine is also known to cause tolerance, physiological dependence, physical dependence, and addiction in such victims when used in combination with heroin (Maisto 244). Morphine also causes respiratory depression but this side-effect is dependent on the concentration of the drug. Therefore, it can cause high or low respiratory rates depending on the starting dose.

Pharmacokinetics: Distribution, Absorption, Metabolism, and Excretion of Morphine

The modes of administration for morphine include, oral, intravenous, intrathecal, epidural, subQ, and rectal. It is also abused through inhalation. However, the most convenient route is IV. The drug is distributed in blood with a peak plasma half-life of 20 minutes. Its metabolism occurs in the liver through the Cytochrome P450 enzymes of phase I and glucuronidation to form morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M3G) during phase II reactions (Ebadi 20). The phase II reactions are catalyzed by the enzyme, UDP-glucuronosyl transferase-2B7 located in the mitochondria of the hepatocytes. Consequently, a single dose of morphine yields about 60% of M3G and 10% M6G. The process of morphine metabolism can also be facilitated in the brain and kidneys. About 87% of the metabolized morphine is excreted through urine. Therefore, the elimination half-life of morphine is about 120 minutes (Ebadi 22).

The Mode of Action of Morphine

The therapeutic form of morphine preferred by many physicians is Morphine Sulfate (Ebadi 32). It acts as an agonist of the mu receptors. These are specific receptors for morphine that occur in nerve cells. These receptors occur in large numbers in the spinal cord particularly on the Substantia gelatinosa region which harbors many receptors for initial pain signal processing. The confirmation of the morphine receptor allows morphine to bind tightly. The receptor contains a flat point to which the aromatic ring gets attached to, a curved region that holds the two carbon atoms, and lastly, the anionic site that houses the tertiary nitrogen atom. When morphine is bound to its receptor in the CNS, it leads to decreased production of neurotransmitters from the affected neurons. The resultant effect is a decrease in the intensity of pain in the affected regions (LeCounter par.4).

Uses of Morphine in Cancer Pain management

Research done on cancer cells indicate that these cells can respond to orally administered analgesics and adjuvants (Hanks 1). This prompted the WHO to develop a program that came to be known as the analgesic ladder which involves a set of sequential steps in the use of analgesics in the management of cancer pain. This program allows different governments and health institutions the flexibility in choosing specific drugs for use. This also involves integrating the disease-modifying remedies and non-drug approaches with the symptomatic treatment drugs used in the management of cancer pains. Through this program, several oral opioids have been employed in the treatment of moderate and severe pains (Hanks 1). Under this program, a set of guidelines were developed concerning the use of morphine. It is documented that the first choice opioid for severe pain related to cancer should be morphine. This should be administered through the oral route in two forms (that is) the normal and the modified release formulations. The guidelines also give the formal method for dose titration which involves the use of the normal release morphine dose. In this case, the drug is administered every four hours. The same dosage is also given for breakthrough pain. The total daily dose of morphine is then reviewed daily to allow for adjustments in the regular dosage (Hanks 2).

The regular dosage is increased just in case the pain returns before the time for the next dose expires. The most preferred formulation for regular dosing is the normal release formulation of morphine. However, this formulation is unavailable in many countries thereby forcing many patients to use the modified type. Additionally, a double dose of the normal formulation is effective in relieving pain overnight for patients who receive the normal release dosage at a four-hour interval. If for some reason the patient cannot take medication orally, the best alternative route of administration is subcutaneous. And for continuous parenteral administration of morphine, the preferred route is subQ infusion. Other alternative routes are recommended depending on the patient’s status (Hawks 2). It is also documented that, for cancer pain management to be achieved effectively, morphine should be used as a step 3 opioid in achieving sufficient analgesia while limiting the occurrence of side effects. It has also been shown that some patients may develop intolerance to orally administered morphine. In this case, alternative opioids are recommended for use.

Morphine Overdose

When one accidentally or intentionally takes too much morphine they risk getting an overdose. Since the drug is highly addictive, cases of overdosing are very common. Overdosing morphine can be fatal and may even lead to death. Research has shown that the minimum lethal dosage for morphine is about 200mg (Maisto 243). However, if the drug causes hypersensitivity, a dosage of about 60mg can lead to death. It causes asphyxia, respiratory depression (high or low respiratory rates), and death. The symptoms of morphine overdose can occur in different parts of the body. The drug causes pinpoint pupils in the eyes, vomiting, and nausea, spasms of the stomach and intestines, and constipation in the gastrointestinal tract. The drug can also affect the heart and its blood vessels thereby causing low blood pressure and weak pulses. Its effects on the nervous system are associated with cases of coma, seizures, drowsiness, and lack of sleep. Additionally, morphine overdose can affect the respiratory system causing shallow breathing, no breathing, slow and labored breathing, or difficulty breathing (Maisto 245). Moreover, its effects on the skin include bluish-colored fingernails and lips.

Patients with morphine overdose are advised to seek early medical attention. Treatment of morphine overdose involves gastric lavaging (involves a healthcare provider pumping the patient’s stomach to force the contents out), inducing vomiting through the use of special oils, administration of charcoal to prevent the absorption and distribution of morphine. Naloxone and Narcan can be used as an intervention to counter morphine overdose. The treatment of patients with extreme cases of poisoning involves supportive care through treatment of the symptoms that arise.

Conclusion

This report entails a detailed account of the chemistry of morphine. Morphine is one of the over 40 alkaloids extracted from opium. It is a potent analgesic also used as a psychoactive agent. Its use as a therapeutic agent dates back to the 14^th Century when it was first used as a painkiller though sparingly. It was also used as a pain killer by soldiers of the American civil war whereby it was reported to have caused extensive addiction among the soldiers. It has found extensive therapeutic application in the 21^st Century especially in pain relief. Heroin is a synthetic form of morphine that is more potent than the parent drug therefore it has been abused over the ages. This makes it a controlled substance however it is recommended for treatment of alcohol and opium addiction.

Despite morphine having numerous uses in relieving different forms of pain such as back pain and chronic pains, it has been shown to have several side effects on the gastrointestinal tract and the respiratory system. It is also highly addictive and therefore it causes tolerance, physiological and physical dependence.

Morphine is administered as its Sulfate form through blood and is transported to target sites in plasma. Its metabolism occurs in the liver where it is converted into inactive conjugate forms that can easily be excreted through urine. The brain and kidneys also facilitate the process of morphine metabolism.

The mode of action for morphine involves acting as a mu receptor agonist thereby reducing the production of neurotransmitters from the affected neurons. It has thus been employed in the management of cancer pain through a program developed by the WHO that enables a stepwise use of analgesics to treat cancer. Large doses of morphine can however lead to an overdose manifested in form of severe symptoms and even death. Therefore, its prescription should be limited to qualified and trained medical practitioners.

Works Cited

Ebadi, Manuchair. Pharmacodynamic basis of herbal medicine (2^nd ed.), Boca Raton: Taylor & Francis Group, 2007. Print.

Hanks, G.N., De Conno, F., Cherry, N., Hanna, M., Kalso, E., McQuay, H.J., Mercadante, S., Meynadier, J., Poulain, P., Ripamonti, C., Radbruch, L., Casas, R.J., Sawe, J., Twycross, R.G. and Ventafridda, V. Morphine and alternative opioids in cancer pain: the EAPC recommendations. British Journal of Cancer; 84.5 (2001): 587-593.

LeCouteur, Penny, and Burreson, Jay. Napoleon’s Buttons: How 17 Molecules Changed History. Penguin Putnam, 2003. Web.

Maisto, Stephen, Galizio, Mark and Connors, Gerald. Drug use and abuse (5^th Ed.). Belmont: Thomson Higher Education, 2008. Print.

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