This essay will be talking about six of the best selling drugs (avonex, zyloric, adalimumab, ventolin, nardil and glucophage), comparing their molecular targets, pharmacodynamic effects and therapeutic uses. A drug can be defined as any chemical other than food that would affect living processes. (http://www.elmhurst.edu/~chm/vchembook/650drugs.html). They have different site of actions, they either act on the cell where they bring about changes in biochemical reactions, acts outside the cell on GI surfaces for example by chemical or physical interactions or acts on receptors found on the cell membrane by physical or chemical interactions. Receptors are proteins found on the sites of the cell membrane that the drug interacts with to exert its pharmacological effect.
Avonex is a form of naturally occurring protein known as interferon beta 1a which helps to fight viral infections. Interferon beta comes from the interferon family, three types of interferons exist, and these are interferon alpha, interferon beta and interferon gamma. They are released by vital infected cells and macrophages. Interferon beta 1a has the chemical formula C908H1408N246O252S7 made up of 166 amino acid. As other interferon beta such as betaferon and rebiff, avonex does not cure multiple sclerosis but helps to slow down the accumulation of physical disability associated with the disease and also reducing the duration and number of relapse and it is the least effective of the three interferon beta1a. Multiple sclerosis is an autoimmune disease that affects the central nervous system and it involves loss of myelin sheath around nerve fibers. The main symptom is the relapsing- remitting flare ups that occur for a day or more. Clinical trials have shown that the drug helps to reduce the rate of relapse by 30% over a period of two years and also patient with early symptom of this disease who are on a weekly injection of avonex for about two years are less likely to develop more complicated symptoms. A study published in the United Kingdom medical journal by lacet suggested in the first year of administration to patients, interferons are very effective but effectiveness decreased after usage for two years and common adverse effect were observed. Avonex (30mcg) is administered to patients once a week intramuscularly and blood test is carried out every three months of the first year of use to check its effectiveness. This is because it is made of protein and carbohydrate hence will be broken down and inactivated by digestive system when administered orally. Although the real mechanism of avonex is unknown , interferon are known to work by binding to type 1 interferon beta receptors (1FNAR1 and IFNAR2c) on human cell surfaces, resulting in the formation of a polymer. The formation of the polymer results in the formation of janus and thyrosine kinases (Jak1 and Tyrk2). The kinases then phosphorylate the receptors by transphosphorylating themselves. The phosphorylated receptors then binds to transcription activators and signal transducers foring another polymer which helps in the acvtivation of antiviral proteins and multiple immunological changes which helps to boost the immune system. Side effects associated with this drug are flulike symptom, liver damage and depression; as a result the drug should not be used in patients with severe depressive illness or with liver diseases.
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Zyloric contains the active ingredient allopurinol, a xanthine oxidase inhibitor used in long term prevention of gout and formation of certain types of kidney stones. The molecular formula is C5H4N4O. Recent research shows that allopurinol is used in the treatment of chronic heart failures and inflammatory diseases. Xanthine oxidase is an enzyme in the body that produce uric acid from purines, and accumulation of this acid in the joint results in gout, the activity of xanthine oxidase is inhibited by allopurinol resulting in lowered levels of uric acid production in the body hence preventing gout and kidney stones formation. The medication can be used in adults and children. Allopurinol is converted to oxipurinol when it is absorbed from the gastrointestinal tract from where it is then distributed in all tissues except the brain. Zyloric (allopurinol) works in two ways in the reduction of uric acid formation. First, it reduces the amount of hypoxanthine and xanthine that is converted to uric acid, hence the amount of hypoxanthine and xanthine needed for reuse in purine metabolic cycle is increased, and in turn overall formation of purine is reduced by a negative feedback mechanism. Normal daily dose of zyloric is 300mg after meal in mild conditions but in more severe conditions higher doses could be administered orally by appropriate divided dosage regimen. Some of the symptoms of overdose are nausea and vomiting and it should be discontinued when allergic reactions occur. Patients on zyloric should be given one quarter of the required dose of 6 mercaptopurine and azathioprine orally when needed; this is because xanthine oxidase inhibition helps prolong their activities.
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Adalimumab, brand name humira, is an injection used to reduce inflammatory effect in patient with severe crohn's disease who did not respond to treatment with immunosuppresants such as azathroprine and rheumatic anthritis. Crohn's disease is a progressive inflammation of the ileum resulting in diarrhoea with abdominal pain and weight loss. Anthritis affects the joints and cause pain. Humira was approved as a TNF Alpha blocker in December 2002. The body's response to injury is inflammation as it helps to repair the injury but it results in pain, fever and diarrhoea in the case of crohn's disease. The protein responsible for inflammation promotion is tumour necrosis factor alpha (TNF), a chemical present in the immune system that triggers other cells to cause inflammation following initial inflammation of infected cells. People suffering from crohn's disease and rheumatid arthritis have large concentration of this protein in their joints and skin. The main job of humira (adalimumad) is to help reduce the production of TNF in order to reduce inflammation. Adalimumab should not be taken by patients suffering from neurologic diseases, those that have history of heart failure and highly infectious patients. It can be prescribed by itself or with non steroidal anti inflammatory drugs which will help ease the pains caused by the inflammation. For crohn's disease,the required adult dose of adalimumab is 80mg initially then 40mg after two weeks on initial dose or 160mg in four divided dose over 1 or 2 days initially then 80mg two weeks after initial dose and then 40 mg on alternate weeks or every week if necessary, the required dose in rheumatic anthritis is 40mg on alternate weeks which could be changed to 40mg weekly if necessary in patients taking just adalimuma. If no response within twelve weeks, then treatment should be reviewed. Some of the side effect associated with adalimumab is headache, rashes, and abdominal pain and urinary tract infections, and these are common in the early stage of treatment.
Ventolin is one of the brand names for salbutamol, the chemical name is 4-[2-(tert-butylamino)-1-hydroxyethyl. In United Kingdom, Salbutalmol became available under the brand name ventolin in 1969. It is used in the treatment of mild to moderate asthma, bronchitis and emphysema by short acting on beta 2 adrenergic receptors. These conditions result in narrowing of airways which makes breathing difficult, salbutalmol opens up the airways hence making breathing easier. Salbutamol results in stimulation of 2-adrenergic receptors and to lower extent 1-adrenergic receptors. This stimulation then results in the activation of adenylase cyclase and accumulation of cAMP, concentration of intracellular calcium ion decrease and methyl transferase activity alteration. As a result of these changes, bronchial smooth muscles are relaxed and mucus clearance by cilia action is increased. Some of the ways salbutalmol can be taken are by: mouth ( 4mg three times daily in sensitive and elderly patients who were initially on 2mg , 400micrograms/kg four times daily for children under two and 1-2 mg three to four times daily for children tow to six years) ,subcutaneous injection ( 500micrograms repeated if necessary every four hours), and aerosol inhalation(100-200 micrograms up to four times a day for persistent symptoms in adults and 100 to 200 micrograms for persistent symptoms up to four times a day for children). The duration of action is between three to five hours. Common adverse effects assosciated with ventolin are nausea, headache, restlessness and anxiety.
Nardil, an anti depressant drug is a brand name for phenelzine. Phenelzine is a monoamine oxidase (MAO) inhibitor used in the treatment of serious cases of depression when other antidepressants have failed to work. The molecular formular of phenelzine is C8H12N2H2SO4. Monoamine oxidase is an enzyme in the body. There are two naturally occurring chemicals (neurotransmitters) in the brain known as serotonin and non epinephrine that maintain mental wellbeing and also prevent depression occurrence. These chemicals are broken down by monoamine oxidase increasing occurrence of depression, phenelzine irreversibly inhibits the activity of monoamine oxidase thus levels of the neurotransmitters are increased as less is broken down, reducing depression occurrence. The recommended dose is 15mg three times daily and this could be increased to four times daily after two weeks and gradually reduced to lowest required dose. The effectiveness of the drug could take up to eight weeks to show up and it is known to affect sleep, therefore should be taken long before bed time. Phenelzine is associated with a large number of side effects and contraindications; this is because it has an effect on the monoamine oxidase in other parts of the body. Some of the side effects are headache, insomnia, anorexia, dry mouth and constipation. The use of phenelzine for kids under sixteen, patients with high blood pressure and those with cardiovascular disease is rare as it is only prescribed to them in extreme cases. Patients on nardil medication should avoid dopamine, cocaine and amphetamines medication, as combination of the medications could result to hypertension problems.
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Glucophage, brand name metformin is an oral medication used in the treatment of type 2 diabetes mellitus. Type 2 diabetes is a disorder that occurs when the amount of insulin produced by the pancreas is lower than the required amount. Insulin is a hormone secreted when blood sugar level are high, it stimulates the uptake of glucose from blood into the tissue and liver to be stored as glycogen, since patients with type 2 diabetes produce low levels of the insulin stimulation of glucose uptake is reduced hence resulting in high levels of glucose in the blood (hyperglycaemia). Metformin reduce the production of glucose and increase its uptake in muscles thus reducing risk of type 2 diabetes. The mechanism of action of metformin is not really known but studies have shown that it could be associated with its ability to activate AMP activated kinase , a metabolic enzyme that increase glucose uptake into muscles. There is a 75% chance of a child getting the disease if both parents are affected and also 60% of patients diagnosed develop some sort of retina damage within 20 years. Side effects associated with metformin are nausea, vomiting and anorexia.