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Pharmacology

Pharmacology Nursing Essay

Introduction

The last few years have been coupled with medical services improvement and, as a result of this; the world has witnessed a constant rise in geriatric population. An increased life expectancy has led to this trend, whereby in the United States proportion of the population aged 50 years and more is projected to grow from 12.4% in the year 2000 to 19.6% in the year 2030 (Public Health and Aging,2003). Based on the United States Census Bureau, 39.6 million of individuals are aged over 65 years and even this number has been projected to hit 72.1 million by 2030, thus accounting for 19% of the US population. In addition, elderly persons who depend on the working adults are expected to rise from 59 dependants per 100 working adults in 2005 to 72 dependants per 100 working adults in 2050. This is because almost all of them are educated and therefore working, thus encountering few difficulties (Williams et al., 2013).

According to available information, an older adult who lives alone is more susceptible to medication errors and thus may need someone who is a bit younger and aggressive to provide direction for him or her. This is majorly because many elderly people do not comprehend medication instructions and may even go to the extent of not adhering to prescriptions. In addition, medication errors among elderly people can also be caused by the number of prescribing providers. Having more than one prescribing provider is more likely to confuse elderly persons and, as such, may result in taking wrong medication and even underdosing or overdosing (Weber, Giannakopoulos, & Canuto, 2011).

It can truly be asserted that many physiological changes are known to occur in the process of aging, which is normally accompanied by a reduction in both general system and organ function. It is general knowledge that aging body systems and organs are less responsive as opposed to the young ones to the effects of drugs. In essence, age-associated changes have a great affect on the response of the patient to the drug therapy since both adverse effects and therapeutic effects are altered. This particular state therefore, creates some specific needs and risks for older adults who undergo drug therapy.

In order to effectively and safely manage drug therapy in older adults, nurses ought to be aware of the fact that numerous older adults normally take over-the-counter and multiple prescribed drugs. Simultaneous taking of drugs is known as “polypharmacy”. A geriatric patient or an older adult is normally defined as being an individual who is either 65 years or more. Older adults are normally categorized into three groups, namely: the young-old who are aged 65-74 years, the middle old who are aged between 75 and 84 years of age, and the “old-old” who are aged 85 years or older. Out of these three categories, the old-old category apart from being the one that is growing extremely fast, it is also the one that has higher medical needs. Therefore, it will have the highest consumption of resources in the society during the next half century.

It can be asserted that the majority of older adults are not only independent, but also in good health. They may, therefore get treatment or drug therapy for some chronic conditions, but most of them are usually associated with normal changes in age. However, it will be important to observe that physiological conditions are normally well-managed or controlled in such older people and, therefore; they do not usually consider themselves as being sick. In addition that, it should be stated that some older adults are not independent and they live with compromised or poor health.    

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Section 1: Psychological Changes that Occur with Aging and Their Effect on Absorption, Distribution, Metabolism, and Excretion of Drugs

Psychiatric morbidities that majorly result from aging of the brain, physical health problems, cerebral pathologies, socio-economic determinants, for instance, reduction in economic independence and a family breakdown are common cases among the elderly population. Numerous psychiatric and physical illnesses complicate provision of drug therapy among the elderly. This is in such a way that pharmacodynamics and pharmacokinetic alterations that occur with aging highly affect the manner in which drugs are taken and how human systems interact with each other. To start with, pharmacokinetic changes that are a result of this unique behaviour include the following:

Absorption

Among elderly people, decreasing gastric acidity coupled with delay in the emptying of the gastric, highly reduced splanchnic blood flow, and a decrease in the intestinal motility play a major role in the slow rate at which drugs are absorbed into the body system. As a result, this leads to delays in the onset or start of action of a particular drug that may have been taken by an elderly patient (CuellarBarboza et al., 2014).

Distribution

Age advancement by an individual is in many cases characterised by an increasing proportion of body fat, which is a result of an increase in elimination of various psychotropic medications. Decreased volume of lithium and hence its high concentration in the body are mainly caused by a decrease in body water as an individual advances in age. This decreased amount of body water eventually results in smaller amount of plasma albumin in the elderly. Since drugs normally dissolve in blood plasma, this case may result in a large proportion of drugs remaining free in blood. Consequently, there is a likelihood of a serious drug reaction in the body. Therefore, due to a greatly decreased cerebral blood flow, drugs available in the brain for action at a particular serum concentration will be decreased to a greater extent (Roels, Mattelaere, & Claikens, 2014).

Metabolism

Elderly people experience a decrease in the mass of the hepatic flow of blood and a decrease in certain body metabolic processes as opposed to others who may be a bit younger. This is because, as one ages, demethylation and hydroxylation levels of the body decrease such that it results in the prolonged action and accumulation of drugs such as chlordiazepoxide and diazepam. This is due to the fact that P-450 CYP2D6 activities of the body system do not actually change with age, but however psychiatric or non-psychiatric drugs can easily result in the changing or alteration of this component and even modification or change of effects of several psychotropics (Vejpongsa & Yeh, 2014).

Once a patient, particularly an elderly one, takes drugs such as fluoxetine, paroxetine, venlafaxine, mirtazapine, and valproate, the activity of P-450 CYP2D6 will be highly inhibited, which will in turn have an effect on metabolism of drugs like desipramine, nortriptyline (TCAs), risperidone, venlafaxine paroxetine, carbamazepine, olanzapine clozapine, and typical antipsychotics (Vejpongsa & Yeh, 2014). When such a case occurs, there is a high likelihood that difficulties and complications will emerge when one tries to treat a given psychiatric disorder of a particular patient. This is likely to force whoever may be in charge to co-administer these medications to achieve some positive results.

Excretion

Age advancement by an individual goes hand in hand with various anatomical changes that specifically take place in the body renal system. The said changes that are most likely to occur as one advance in age include loss of glomeruli, renal mass, thickening of the membrane’s basement of tubules and glomeruli, and intimal thickening of the arterioles coupled with obliteration of arterioles located in cortical glomeruli. As a result, the filtration rate of the glomerular will be reduced or minimized significantly. This poses a threat to normal operation of the body because the rate of filtration and the renal work will be highly minimized or reduced. In such case, there occurs accumulation of drugs, for instance, lithium and rivastigmine that might have been taken in normal dosage by a patient in an advanced age. Therefore, such an individual is most likely to suffer from severe drug toxicity, which constitutes a serious health problem (Suzuki, Hashimoto, Anzai, & Nagasawa, 2014). 

Section 2: Factors that Predispose Older Patients to Adverse Drug Reactions

Response to drugs taken by an elderly individual is slow as a result of the above-mentioned reasons. Furthermore, senior-aged people also experience adverse drug reactions, which may happen due to the following factors:

Age

Elderly patients who may be experiencing multiple health problems normally have an adverse drug reaction. This is usually the case because at this age the rate of drug absorption and metabolism in the body system is comparatively slow due to reasons that have been mentioned before. Therefore, once drugs are taken, they accumulate consecutively up to a toxic level that may as well lead to other more serious health problems. In addition to this, older people in many cases have various health complications and, as such, they will buy several over-the-counter drugs (OTCs) and have several prescriptions from medical practitioners. This may lead to high rates of drug consumption, which may accumulate in the body due to a low absorption rate caused by decreased body water and a higher amount of tissue fat (Pavelets, Lobanov, Vavilova, & Latsko, 2014).

Creatinine Clearance Category

This refers to the function of the kidney, which plays a major role in the excretion of drugs that might have been taken. As an individual advances in age, there is a change in renal profile and many elderly people usually have kidney diseases, which affects drug clearance and metabolism in the body. Therefore, increased accumulation of drugs due to the kidney’s failure leads to an adverse drug reaction in the elderly.

Body Weight Fat Distribution

Drugs are distributed to and from the body mainly by dissolving in cellular body fluids. However, as an individual grows old, the water percentage of his or her body decreases and there is an increased disposition of fats. Therefore, there is a higher concentration of fats in the body than water. Since taken drugs have to be absorbed by cellular fluids, mainly water, for easy transportation, this will not take place, thus leading to their accumulation in the body and an adverse reaction when they reach a toxicity level.

Alcohol Drinking

The majority of elderly people are associated with taking alcohol in their free time. Alcohol alters the metabolism of various drugs and interaction with other drugs, which may be harmful to the patient’s body. Increased consumption of alcohol has an effect of activating enzymes that play a role of transforming taken drugs into harmful substances that damage the liver and other body organs. As a result, metabolism processes of drug absorption and transportation are greatly hindered, thus resulting in toxic drug accumulation and adverse reactions within the body (Kitachev et al., 2014).

Polypharmacy

Many elderly people normally suffer from more than one disease and, therefore; they will have to take several drugs whether they are prescribed or over-the-counter. Sometimes, when drugs are combined, synergistic toxicity may occur, hence causing adverse reactions in the body of a patient.

Section 3: 1.Classes of Medication

 This section will focus on two classes of medications namely antihistamines and antidepressants. In each class of medication, 3 commonly prescribed medications and their mechanism of action, 3 commonly used non-prescriptive medications and their mechanism of action, and 3 complementary therapies and their mechanism of action will be discussed.

Antihistamines

Antihistamines are medications used for the treatment of allergies. Some of the common allergies treated by antihistamines include allergic conjunctivitis, urticarial, allergic skin conditions, allergic rhinitis, hay fever among others. Antihistamines are commonly available in forms such as nasal sprays, gels and lotions, creams, capsules, and tablets (Simon & Simons, 2008). Most of the antihistamines medications are available over the counter; however, some of them may require prescription. Commonly prescribed antihistamines covered in this paper include Clarinex, Xyzal, and Elestat. This section has also discussed three commonly used over the counter antihistamines namely Allegra, Zyrtec and Claritin.

Clarinex, Xyzal and Elestat Prescription Antihistamines and their Mechanism of Action

There are many commonly prescribed antihistamines, but this section will focus on three namely clarinex (desloratadine), xyzal (levocetirizine), and elestat (epinastine).  Clarinex (Desloratadine)

Clarinex is available in form of tablets and oral solution. Clarinex tablets contain 5mg desloratadine as well as the following compounds: polyethylene glycol, dibasic calcium phosphate dehydrate USP, titanium oxide, talc USP, corn starch NF, among others. Its oral solution contains o.5 mg/1ml desloratadine and a number of inactive compounds such as sodium benzoate NF, propylene glycol, purified water USP, and sorbitol solution USP (Small & Kim, 2011). Clarinex is a histamine antagonist with selective histamine H1- receptor activity. Desloratadine with a concentration of 2-3ng/ml interact very well with histamine H1- receptor (Simon & Simons, 2008). Desloratadine powder is very soluble in propylene gycol and ethanol, but slightly soluble in water.

Xyzal (Levocetirizine)

Xyzal is also available inform of tablets and oral solution. Its tablets contain a number of inactive elements such as titanium dioxide, magnesium stearate, microcrystalline cellulose, and hypromellose (Small & Kim, 2011). Its solution form contains inactive elements such as purified water, sodium acetate trihydrate, methylparaben, saccharin, and maltitol solution. Xyzal is a locally active, direct antagonist of histamine H1- receptor and a suppressor of the release of histamine from the cell (Simon & Simons, 2008).

Elestat (Epinastine)

Elestat is a solution that contains epinastine HCL and is administered to the eyes. It also contains benzalkonium chloride as a preservative. Other inactive elements in elestat include sodium hydroxide, edatate disodium, sodium phosphate monobasic, sodium chloride and purified water.  Elestat is a histamine H1- antagonist. It is a selective inhibitor of histamine H1- receptors (Simon & Simons, 2008). Epinastine has affinity for histamine H2- receptor and is a selective for histamine H1-. Epinastine also has affinity for 5-HT2-, α1, and α2 receptors (Simon & Simons, 2008).   

Allegra, Zyrtec and Claritin OTC Antihistamines and their Mechanism of Action

Most of the over the counter antihistamines belong to four generic names namely fexofenadine, cetirizine, loratadine, and acrivastine. There are many over the counter antihistamines in these generics, but this section will only focus on three: Allegra (fexofenadine), Zyrtec (cetirizine), and Claritin (loratadine).

Allegra (fexofenaidine)

The active element of Allegra is the fexofenadine hydrochloride. Allegra is a histamine H1- receptor antagonist which is available in three forms: oral suspension, ODT, and tablets. The tablet contains 180, 60, or 30mg fexofenadine hydrochloride (Simon & Simons, 2008). The inactive elements contained in the tablet include pregelatinized starch, microcrystalline cellulose, croscarmellose sodium, iron oxide blends, among others. The ODT tablet contains 30 mg fexofenadine hydrochloride with a number of inactive elements such as aspartame, povidone K-30, citric acid anhydrous, mannitol, etc. (Small & Kim, 2011). The oral suspension contains 6 mg fexofenadine HCL per ml and a number of inactive elements such as xylitol, propylene glycol, cream flavour, sodium phosphate dibasic heptahydrate, edeate disodium, titanium dioxide among others. 

Allegra mechanism of action involves blocking histamine H1- receptors on cells. By blocking the histamine receptor, it prevents the activation of histamine receptor. In other words, Allegra offers exclusive suppression of peripheral histamine receptors. It has negligible antiserotonergic or anticholinergic activity and it is not likely to penetrate to the blood, and thus, it does not cause drowsiness unless one takes an overdose (Simon & Simons, 2008).

Zyrtec (cetirizine)

The active element in Zyrtec is cetirizine hydrochloride, which is selective and orally active histamine H1- receptor antagonist. It is available in three forms: tablets, chewable tablets, and syrup. Oral tablets are available in 10 and 5 mg strengths with a number of inactive elements such as titanium dioxide, polyethylene glycol, lactose monohydrate, colloidal silicon dioxide, etc. The chewable tablet is also available in 10 and 5 mg strengths. Its inactive elements include carmine, acesulfame potassium, blue dye, mannitol, betadex NF, cellulose, among others (Simon & Simons, 2008). When in the syrup form, it contains 1 mg/ml cetirizine hydrochloride with several inactive elements such as water, glacial acetic acid, banana flavour, sugar syrup, glycerine, etc. (Simon & Simons, 2008).

Zyrtec mechanism of action involves blocking histamine H1- receptors on cells. By blocking the histamine receptor, it prevents the activation of histamine receptor. In other words, Zyrtec offers exclusive suppression of peripheral histamine receptors. It has negligible antiserotonergic or anticholinergic activity and it is not likely to penetrate to the blood, and thus, it does not cause drowsiness unless one takes an overdose. Cetirizine can powerfully suppress flare and wheal reaction at dose of 5-10 mg after intradermic histamine injection in adults and children (Buck, 2010).

Claritin (loratadine)

The active element of Claritin is the loratadine. It is available in three forms namely tablets, syrup, and rapidly-disintegrating tablets. In its tablet form, it contains 10 mg micronized loratadine with the following inactive elements: magnesium stearate, lactose, and corn starch. In syrup form, it contains 1 mg/ml micronized loratadine with a number of inactive elements such as water, citric acid, sugar, edetate disodium, among other. The rapidly-disintegrating tablets contain 10 mg with inactive elements like mint flavour, mannitol, gelatin, and citric acid (Simon & Simons, 2008).

Claritin mechanism of action involves blocking histamine H1- receptors on cells. By blocking the histamine receptor, it prevents the activation of histamine receptor. In other words, Claritin offers exclusive suppression of peripheral histamine receptors. It has negligible antiserotonergic or anticholinergic activity and it is not likely to penetrate to the blood, and thus, it does not cause drowsiness unless one takes an overdose (Small & Kim, 2011).

Antidepressants

Antidepressants are drugs used for the treatment of depression. These drugs can also be used several other medical disorders such as post-traumatic stress disorder (PTSD), generalised anxiety disorder (GAD), and obsessive-compulsive disorder (OCD). In some cases, these drugs are used for the treatment of people with chronic (long-term) pain (Perveen, Razi, Haider, Qayyum, & Haleem, 2013). Their mechanism of action is not well understood, but they are thought to work by increasing neurotransmitters in the brain. Although antidepressants are capable of treating symptoms associated with depression, they are not capable of addressing the causes of depression. There are so many types of antidepressants, but the most common ones are SSRIs (Selective Serotonin Reuptake Inhibitors), MAOIs (Monoamine oxidase inhibitors), and Tricyclics antidepressants (TCAs) (DeVane, 2006). The three are prescription medications. Over the counter antidepressants include St John’s wort, folic acid, and omega 3.

SSRI, TCA, and MAOI Prescription Antidepressants and their Mechanism of Action

The most commonly prescribed type of antidepressants is the SSRIs. They are normally considered best because they cause fewer adverse effects. Another thing that makes these drugs popular is that even an overdose cannot result to a serious problem. Other antidepressants that are also prescribed include TCAs and MAOIs. Examples of SSRIs include fluoxetine, sertraline, paroxetine, citalopram, escitalopram, and fluvoxamine. Examples of TCAs include nortriptyline (Allegron), lofepramine (Gamanil), and imipramine (Tofrani). Examples of MAOIs include phenelzine (Nardil) and moclobemide (Manerix) (Moncrieff & Cohen, 2006).

SSRIs

The mechanism of action for SSRIs is normally presumed to be associated to its inhibition of the “CNS Neurol uptake” of 5HT or serotonin.  (Perveen, Razi, Haider, Qayyum, & Haleem, 2013). SSRIs block uptake of “Serotonin” into the human platelets and they are also selective inhibitors of the “neuronal serotonin” reuptake. In addition to that, they are also known to have weak impacts on both dopamines neuronal and norepinephrine (Perveen, Razi, Haider, Qayyum, & Haleem, 2013).

TCAs

Function by increasing the amount of norepinephrine in the brain and to some extent it is also increases the serotonin levels. Some TCAs mechanism of action also blocks the action of acetylcholine and histamine. Because of these actions they are also used for other treatments too (Moncrieff & Cohen, 2006).  

MAOIs

Mechanism of action involves blocking the monoamine oxidase, which in turn increases the levels of dopamine, serotonin, and norepinephrine. Inhibiting the monoamine oxidase also increases the levels of tyramine in the body, which could lead to an increase of blood pressure. This may lead to a hypertensive crisis (Perveen, Razi, Haider, Qayyum, & Haleem, 2013).

John's Wort, Folic Acid and Omega 3 OTC Antidepressants and their Mechanism of Action

It is not likely to find the non-prescribed (over the counter) antidepressants because depression is not specific disease that does cause physical pain. Therefore, people are not likely to look for depression medications from a pharmacy. However, some medications can be offered over the counter. This section will focus on three over the counter medications namely: St John’s wort, folic acid, and omega3.

St. John's wort

 The correct mechanism of action of St John’s wort is not known, but it blocks serotonin reuptake and changes the levels of γ-aminobutyric acid, norepinephrine, dopamine, as well as other neurotransmitters (Nahas & Sheikh, 2011).

Folic acid

Mechanism of action involves boosting one or more of the 3 monoamines: dopamine, serotonin, and norepinephrine. It acts as a critical regulator of tetrahydrobiopterin, which is an important co-factor of the synthesis for trimonoamine neurotransmitter. By improving the synthesis of trimonoamine neurotransmitter, it offers the antidepressant actions (Stahl, 2007).

 Omega 3  

Omega-3's (DHA and EPA) together with antidepressants may be more effective than antidepressants alone (Logan, 2003).Works by regulating the serotonin reuptake in the brain (Perveen, Razi, Haider, Qayyum, & Haleem, 2013).

Complementary Therapies for Controlling Allergies

Honey: Honey is believed to reduce allergic symptoms though there is little scientific evidence. However, people who are allergic to bee stings or pollen, as well as children under the age of 1 year should not take honey.

Butterbur extract: Butterbur herb has the capability of reducing the symptoms related to nasal allergies. Nonetheless, there are still safety concerns about this herb.

Nasal saline irrigation: There is sensible evidence that putting salty water into one of your nostril and running it out with the other can reduce allergy symptoms. This method is considered safe, but devices being used to conduct it should be cleaned and used in the correct manner. Unsafe water should be used in nasal saline irrigation.

Acupuncture: Acupuncture treatment is also associated with seasonal allergy relief. However, how this treatment works is not clear.

Complimentary Therapies for Controlling Depression

Yoga: Physical exercises usually play a major role in attaining body and mind control. Physical exercises help to relax the body and are therefore considered as the most appropriate for people with depression.

Acupuncture: This is an ancient technique, during which fine needles are placed at superficial parts of the skin for given a period of time so that nerves of a person are awakened, therefore releasing natural painkillers.

Color therapy: It is assumed that a given colour may affect an individual’s mood and, thus, colours can be used so as to solve the problem of depression.

Massage: It plays a key role by helping to ease tension within muscles and reducing mental and emotional anxiety experienced by an individual who is depressed.

Section 4: Potential Drug Interaction

Combining antihistamines with other drugs can alter their effect. It is always advisable to avoid drug interaction where possible because its effects may be unpredictable and potentially severe. When taking first-generation antihistamines, one should avoid the following types of medication: tricyclic antidepressants, benzodiazepines, MAOI antidepressant, and sleeping tablets. There no important interaction for most of the second-generation antihistamines; however, one should not take second generation antihistamines with mizolastine or rupatadine. It is also not advisable to take cold and cough medicines with antihistamines (Simon & Simons, 2008).

Though there can be drug interaction between antidepressant with other substances, most of them are not clinically significant. MAOIs and TCAs may have clinically significant interactions but the newer compounds SSRIs do not have any significant interactions because of their selective mechanism of action. Some of the drugs that should be avoided include benzodiazepines, warfarin, buspirone, antiepileptics, tramadol, and lithium (DeVane, 2006).    

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Conclusion

Elderly people suffer from a myriad of complications associated with their age. Therefore, good healthcare should be provided and better medications should be available for them. It is critical to note that most serious health problems such as depression and high blood pressure are evident among the elderly as a result of their life patterns and living standards. It is important that healthcare concerned with caring for the elderly people become aware of the relevant medication which can be used to treat them appropriately. Appropriate drugs should be used to treat elderly people to ensure they live longer. Factors that predispose older patients to adverse drug reactions include age, creatinine clearance category, body weight and fat distribution, alcohol drinking, and polypharmacy.

Antihistamines are medications used for the treatment of allergies. Most of the antihistamines medications are available over the counter; however, some of them may require prescription. Commonly prescribed antihistamines covered in this paper include Clarinex, Xyzal, and Elestat. This section has also discussed three commonly used over the counter antihistamines namely Allegra, Zyrtec and Claritin.

Antidepressants are drugs used for the treatment of depression. These drugs can also be used several other medical disorders. Their mechanism of action is not well understood, but they are thought to work by increasing neurotransmitters in the brain. There are so many types of antidepressants, but the most common ones are SSRIs (Selective Serotonin Reuptake Inhibitors), MAOIs (Monoamine oxidase inhibitors), and Tricyclics antidepressants (TCAs) (DeVane, 2006). Over the counter antidepressants include St John’s wort, folic acid, and omega 3.

There are many complementary therapies that can be used to treat allergies and depression. Some of the complementary therapies that can be used to control allergies include honey, butterbur extract, nasal saline irrigation, and acupuncture. Complementary therapies that can control depression include yoga, acupuncture, color therapy, and massage. Combining antihistamines with other drugs can alter their effect. It is always advisable to avoid drug interaction where possible because its effects may be unpredictable and potentially severe. Though there can be drug interaction between antidepressant with other substances, most of them are not clinically significant.

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