Routes of Drug Administration - Coursework Example

Routes of Drug Administration 2009 Routes of Drug Administration In medicine, a route of medication/drug administration is the way by which a medication in any form is delivered to the target site. Any medication is useless unless it gets into contact with human body and is transported to the place where its effects are needed. Numerous routes of administrations available these days involve different transport mechanisms of the body to fulfill this goal. Oral Route Oral administration route is the eldest method of drug delivery. Amongst the variety of medication delivery routes, oral administration is reported to be the most preferred route for both the clinician and the patient (Shojaei, 1998). This method has several considerable advantages relating to convenience, safety and cost that make it probably the most often used one. Firstly, oral administration involves no pain and is characterized by relative ease for the clinician and the patient. Secondly, since this method does require any additional expenses for either production of orally administered drugs or their administration to patients, it is reasonably considered to be the cheapest. Thirdly, this method offers great variety of choices for the clinician who can, depending on the patient’s needs, administer fast or slow release tablets, suspensions/mixtures or solid medications, etc (Singh & Kim, 2006). Mobility and absence of need to sterilize or use specific devices/machines also contribute to the popularity of oral administration route. While the advantages of oral route are significant, it also has several essential shortcomings relating, for the most part, to the fact that drugs administered orally move through the digestive tract. Firstly, some orally administered medications begin to absorb in the mouth and stomach though typically absorptions begins from the small intestine. On its way to the target organ, the medication passes through the intestinal wall and is further transported to liver. Both these pathways chemically alter many medications which results in decreased amounts of medication carried to the target site. Therefore, such medications are distributed orally in larger doses to compensate for the loss due to liver and intestinal wall related metabolism, while, for example, intravenous administration of the same medications does not involve any chemical alterations and, subsequently, smaller doses are needed to have the same effect. Besides, many medications are inadequately absorbed in the digestive tract or, furthermore, are neutralized by the influence of digestive enzymes and stomach acid (Beers & Berkow, 1999). Secondly, oral administration of medications involves interference with food in the digestive tract as well as other orally administered medications. In many cases such interference affects significantly the amount and speed of the medication absorption. Although special rules exist for each medication administered orally (some shall be taken with food, others on an empty stomach or in combination with certain other drugs that facilitate absorption, etc), still this factor is essential enough to make many medication inappropriate for oral administration (Singh & Kim, 2006). Thirdly, many medications irritate the digestive tract when taken orally. The most common example of such medication is aspirin in any form as well as the majority of other medications that have nonsteroidal anti-inflammatory effects: they negatively affect the lining of both human stomach and small intestine in many cases producing (worsening) ulcers (Singh & Kim, 2006). And finally, other medication administration routes may be needed in cases involving the following: the patient’s inability to take anything by mouth, the need for very precise dose or rapid effect, and high doses/quantities of drugs are also administered using other routes. Inhalation Although inhalation is, similarly to the oral route, also an old method of medications delivery to the target organ, it was not until the last century that inhalation turned into a foundation of increasingly popular respiratory care. The scientific underpinning for respiratory care also termed ‘aerosol therapy’ appeared only in the mid-1970s, after the 1974 Sugarloaf Conference. Early facts on the medication-delivery effectiveness of the aerosol delivery devices commonly used those days (such as MDI, DPI, and nebulizer) demonstrated that lung deposition only reached up to 15 percent of the nominal dose, which significantly limited the use of this delivery method. However, despite this shortcoming pertaining mostly to the early imperfect devices, the data also showed several highly advantageous characteristics of the inhalation route. In many aspects, the revealed advantages of inhalation were critical enough to make it the preferred method of drug administration in many cases (Beers & Berkow, 1999). Firstly, inhaled medications are localized to the target organ and, therefore, smaller dose of medications is required that, for example, in case of oral administration or injection. The smaller is the dose, the fewer are adverse effects on the patient. Furthermore, substantial improvements in the design of respiratory devices improve the efficiency of the method while the old-time benefits also remain in place. Secondly, the method of inhalation allow for rapid absorption of medications which pass the liver on their way to the target site (Rau 2005). However, inhalation also has some disadvantages that noticeably limit its use. While absorption of gaseous substances is fairly efficient, no solids or liquids can be administered via this route if larger than 20 micron only. Besides, serious differences among inhalation devices create usability related challenges to the patient as well as complicate clinician instruction. Probably further improvements in terms of drug loss reduction and functionality, coupled with the introduction of a single universal standard might remove some of the existing shortcomings (Rau, 2005). Intravenous Injection Administration of medications via intravenous injection is a relatively novel and complex method. It is definitely the quickest method of delivery to the target site: the medication is injected directly into blood. Intravenous delivery of medications comprises two major methods: intravenous drip (continuous delivery of liquid medications or fluids through a specific intravenous access device) and intermittent infusion (medications are delivered periodically when the patient requires them). Intravenous injection of medication using a syringe and a needle inserted into the patient’s vein is the most ordinary form of intravenous delivery. Most often medication is injected into the arm vein which shall be prepared properly (bulged) prior to injection. However, while such injection is the easiest and quickest option to administer medications in acute therapy or emergency care unit, other types of intravenous therapy that allow for continuous systematic delivery are normally used in a controlled health-care setting (Beers & Berkow, 1999). Intravenous route is the most reasonable and preferred choice when highly precise dose of medications must be administered or a highly irritating solution must be delivered to the patient’s body (other methods are likely to cause much pain and/or damage tissues in the latter case). On the other hand, the method of intravenous injection is associated with more difficulties than other types of injection, let alone oral delivery: it may often be difficult for the clinician to properly insert a needle into the patient’s vein. Intravenous route involves immediate delivery of mediation to the bloodstream and, therefore, the effect is produced incomparably quicker than in case of any other route. On the other hand, the effect of intravenously injected medication lasts for a shorter time, and continuous or systematic injection must be used in cases when constant effect is required (Beers & Berkow, 1999). Besides, a number of risks are associated with either type of intravenous delivery. Firstly, any intravenous injection involves damage of the skin which leads to increased risk of infection. Secondly, infiltration of some medication (accidental penetration into the tissues surrounding the vein) may cause serious damage. And finally, embolism (occasional penetration of an air bubble or solid particle) may also occur and in some, though very rare, cases lead to adverse effects and even death (Maki, 1994). Sublingual Route Several types of popular medications are administered via this route. Typically, these medications are in the form of tablets to be held in the mouth or under the tongue to dissolve. Most often these tablets are designed to dissolve slowly. Nitroglycerin and nicotine containing chewing gum are probably the most common examples of medications administered sublingually. The advantages of this method include the following: absence of chemical alterations in live or digestive tract, rapid absorption due to intensive blood supply in the mouth, and stability due to neutral pH level in the mouth. On the other hand, it is not always convenient for the patient to hold medications in the mouth and despite goods absorption only small dose can be administered this way (Wheelera & Sharif, 1996). Transdermal Route This route is used to deliver to the target site many specific medications, and in each case the clinician’s decision regarding use of this method relies on full consideration of several factors. These factors include the site of application, thickness and integrity of the stratum corneum epidermidis, size of the molecule, permeability of the membrane of the transdermal drug delivery system, state of skin hydration, pH of the drug, drug metabolism by skin flora, lipid solubility, depot of drug in skin, and alteration of blood flow in the skin by additives and body temperature (Committee on Drugs, 1997) All systems that rely upon transdermal route of medication delivery have one common shortcoming: the clinician is hardly able to limit medication uptake and control its toxic effects. This concern is especially topical in pediatrics because children’s skin and blood flow in the skin facilitates intensive absorption. On the other hand, the advantages of this method are essential too: the transdermal route bypasses liver and other organs that can alter its chemical composition; transdermal administration is relatively easy to administer and does not require any complex systems which reduces cost of treatment; it is the best option when prolonged or systematic effects are needed (Barry, 2002). Examples of drugs currently administered by the transdermal route include scopolamine patches to prevent motion sickness;18,25–29 a eutectic mixture of local anesthetics (EMLA) cream to reduce the pain of procedures;30–34 corticosteroid cream administered for its local effect on skin maladies;35 TAC for anesthesia when suturing small lacerations;36,37 and fentanyl patches to treat cancer pain or chronic pain syndromes.38–41 Episodes of systemic toxic effects, including some fatalities in children, have been documented with each of these, often secondary to accidental absorption through mucous membranes (Committee on Drugs, 1997). Conclusion Evidently, each of the routes described above has unique features that can be considered either advantages or shortcomings depending on the situation. Different combinations of features that characterize each delivery route contribute greatly to the effects of medications on the patient because the outcomes of identical treatment may vary immensely depending on the route of drug administration. Thus, some medications are absorbed inconsiderably from the gastrointestinal tract, but if injected intravenously produce observable results. Patients preferences coupled with the situation of use also seem to seriously influence the choice of administration route. Thus, oral route is mostly preferred by the patient as it involves no pain or complex preparations. However, the limitations of this method (absorption limitation, metabolism, etc) make it irrelevant in many cases. Similarly, though transdermal administration may be used as a valid replacement for oral route in some cases, only limited number of medications is suitable for this delivery pathway. Furthermore, neither of these routes is likely to be the first choice in emergency treatment and intensive care units where injection with its advantages perfectly suits the purposes of intensive and emergency treatment in terms of quickness and reliability. Therefore, it will be reasonable to state that the route of drug administration in each case shall rely on analysis of the following factors: the characteristics of the medication to be administered and the purpose of treatment, namely quickness and duration of effects, the need to bypass liver and/or digestive tract, etc. No single route or method of medication administration can be considered to be the ideal option for all medications in all circumstances, and, therefore, further research is critical to determine the most effective delivery route for each medication. References Barry, B. W., 2002, ‘Drug delivery routes in skin: a novel approach’, Advanced Drug Delivery Reviews, 54, Supplement 1, pp. S31-S40 Beers, M. H. & Berkow, R., 1999, The Merck Manual of Diagnosis and Therapy, 17th Edition, John Wiley & Sons Committee on Drugs, 1997, ‘Alternative Routes of Drug Administration – Advantages and Disadvantages (Subject Review)’, Pediatrics, Vol. 100 No. 1 July 1997, pp. 143-152 Maki, D. G., 1994, ‘Infections caused by intravascular devices used for infusion therapy: Pathogenesis, prevention, and management’, In: Bisno, A.L., Waldvogel, F.A. (Eds), Infections Associated with Indwelling Medical Devices, 2nd ed. Washington DC: American Society for Microbiology, pp. 155-212. Rau, J. L. 2005, ‘The inhalation of drugs: advantages and problems’, Respiratory Care, 50(3), pp. 367-82 Shojaei, A. H., 1998, ‘Buccal Mucosa as a Route for Systemic Drug Delivery: a Review’, Journal of Pharmacy and Pharmaceutic Science, 1 (1), pp. 15-30. Singh, N. B. & Kim, K. H., 2006, ‘Drug Delivery: Oral Route’, Encyclopedia of Pharmaceutical Technology, Academia of Pediatrics Wheelera, A. W, & Sharif, S, 1996, ‘Sublingual delivery of vaccines: Can we enhance the immune response induced via this route?’ European Journal of Pharmaceutical Sciences, 4, Supplement 1, Page S39 Read More