Routes of drug administration
- 1. Name Laraib Tariq Department pharm D Semester 3rd Subject Pharmacology Topic Routes of drug administration
- 3. ROUTES OF DRUG ADMINISTRATION: Definition: Route of administration is the pathway followed by any substance ( drug, fluid, poison etc) to reach into body (targeted area). Route of administration affects the drug bioavailability and help us to determine the pharmacological effects. Various properties can determine the route of drug administration e.g; 1.Properties of drug (water, lipid soluble, ionization) 2.Therapeutic effect (rapid or slow onset of action)
- 4. Following are the routes of drug administration.
- 6. ENTERAL ROUTE: The safest, popular and simple form of medication is enteral administration (by mouth) into GI track. Both ends of GIT can be utilized, the mouth and the anus. The medication can be taken by several ways e.g can be positioned under the tongue( sublingual), between the gums( buccal) and cheeks. They promotes the direct absorption into the bloodstream. Enteral administration involves esophagus, stomach, small and large intestine. The most common route in enteral is by ingesting them orally.
- 8. 1. Oral route: The first and best choice of drug administration is oral route since it is convenient .Neither special knowledge nor special supplies are required( syringes, needles). The instructions are easily understandable to the patients, reducing the visit to the health centre. So it is advantageous to both patients and physician. Can be easily self administered, without need of doctor. In some cases oral route is advantageous (toxicities can be reversed by binding to activated charcoal) but also not suitable for drugs which are affected by harsh acidic environment of stomach (low gastric ph inactivates the drug).
- 10. GASTRIC RESISTING PREPARATIONS: Sometime drugs are targeted to GI sites such as for heart burn purposes, then in this case oral route is best way of administering drugs. Therefore they must be absorbed from GI system to gain access to systemic circulation and reach the site of action. In this case drugs may be affected by GIT environment because some drugs are poorly absorbed in GIT( heparin) or some become irritating to stomach(aspirin). So in order to keep drug safe to reach into body, two types of preparations are available. 1.Enteric coated preparations. 2.Extended release preparations.
- 12. 1:ENTERIC COATED PREPARATIONS: It is the polymer barrier that protects the drug release from stomach acidic ( ph 3) environment to the intestine less acidic ( ph 7-9 alkaline) environment. It is also an efficient way to achieve drug target. Sometime certain Anthelmintic need to achieve high concentration in certain sections of intestine so enteric coating is best for such dosage form. So all the drugs which are damaged by stomach secretions or cause gastric discomfort are administered in this form. Like aspirin, omeprazole etc cause severe gastric discomfort, for such preparations enteric coating tends to avoid activation and in mouth and esophagus.
- 13. These preparations takes time from 30 mints to 7 hours to reach to the intestine depending upon the type of food present in stomach. Fatty acids, waxes, plant fibers and plastics are use for enteric coatings.
- 14. 2:EXTENDED RELEASE PREPARATIONS: Extended release drugs have special coatings that promotes the slow release of drug in GI fluids. It increase patient compliance and maintain concentration within therapeutic range for a long period of time as compared to immediate release dosage forms. Have duration of 8 hours or longer.
- 15. ADVANTAGES OF EXTENDED RELEASE DRUGS: Decrease in frequency of administration of drug relative to other dosage forms Maintain therapeutic range Lessens the intensity of undesired effects Lessens the drastically increase in blood level after administration of other dosage forms. Beneficial for drugs having short half life. For example 2 doses of extended release morphine are enough for pain relief relative to oral morphine which is administered six times a day having half life of 2 to 4 hours.
- 18. SUBLINGUAL ROUTE: Sublingual means to place the drug under the tongue and buccal means to place between cheek and gums as there is high capillary network and promotes the drug to enter the systemic circulation. This route is significant for highly soluble drugs by preventing the first pass affect e.g nitroglycerine. If we take nitroglycerine by oral route than more than half is cleared by first pass effect.
- 20. PARENTAL ROUTE: This route introduces the drug directly into systemic circulation. It is route of choice for drugs that are poorly absorbed or unstable in GIT( insulin and heparin), for unconscious patients or for rapid onset of action. This pathway is good because it do not follow first pass effect and have high bioavailability.
- 22. TYPES OF PRENTERAL ROUTE:
- 23. 1:Intravenous (IV): It is helpful for non orally absorbed drugs. IV allows speedy affect and full level of control over the amount. It provides 100% bioavailability. No absorption relevant factors are found in IV because there is rapid and full bioavailability. The patient response is accomplish with a precision which is not possible by other doses. It is the singe way of giving the irritating solutions because if we inject drug slowly then blood dilutes considerably. It is good for localize affects because drug is injected directly into artery.
- 24. Usually for patient comfort, veins of forearms( basal and middle cephalic vein) or in the wrist( cephalic accessory and medial ante-brachial) are most common sites for IV. In certain cases, it may be necessary to resort to a central IV route, which consists in a catheter located at the outlet of the superior vena cava (right atrium). This is required when it is not possible to channel peripheral routes, for prolonged treatments or when hypertonic solutions must be administered.
- 26. Fast IV injection: The administration of single dose directly into the vein but in a small volume. By this way the medication diluted in the venous system is directly enter into the heart, pumped to the lungs and spread to the rest of the body. Therapeutic affect start within 20 t 40 seconds thus useful route for emergencies and pain management. Slow IV injection: Administration into vein but in a large volume and for a long period of time. Here medication enter the body by infusion pump, forcing the solution to pass the catheter inserted in a vein.
- 28. 2:Intramuscular injections (IM): It is the administration of injection directly into the muscle in different areas. 1. Upper part of arm: deltoid muscle is best target in this case but it may be painful for patients because this area has higher rate of absorption. 2ml amount is injected. 2. Glutes: dorsogluteal muscle is site of action in this case. Here the rate of absorption is slow because of high amount of adipose tissues.7-8ml amount is injected. 3. External thigh phase: vastus lateralus muscle are targeted in this phase. This phase is usually for babies and infants due to incompletely develop muscles. It may causes high risk of nerve damage.5ml amount is injected. Aqueous solution medication are quickly absorbed depending on the blood flow to the injection site. Some time local heat, massage, or exercise can be modulated to some degree.
- 31. AQUEOUS AND DEPOT PREPARATIONS: Aqueous solutions are absorbed rapidly relative to depot preparations which has slow absorption because they consist of suspension of drug in non aqueous vehicle like polyethylene glycol. First drug diffuse out of the muscle then precipitates the site of action. It dissolves over an extended period of time. Examples are haloperidol (sustained release drug) and medroxyprogesterone.
- 32. 3:Subcutaneous (SC): It is the administration of drug injected under the skin into the adipose layer beneath the dermis. So that is why also called hypodermic administration. It is slower than IV injection. It provides the constant and uniform affect. It is used for drugs that are not irritating to the tissues otherwise causes severe pain and necrosis. It provide prolong and slow action. We can alter the period of drug absorption as in insulin injections depending upon the particle size, protein complexation and Ph. Drug absorption implanted under the skin in a sold pellet form occur slowly over weeks or months. This route is affected for certain hormones e.g contraceptives.
- 33. It is applied on the external side of arm or thigh or on the anterior face of abdomen. Usually injected smaller amount than IM. It minimize the risk of hemolysis or thrombosis as occur in IV.
- 35. IV ,IM AND SC INJECTION:
- 36. OTHERS: 1: Oral inhalation: Route for inhalation both oral and nasal gives the quick delivery of medication due t large surface area of mucous membrane in respiratory and pulmonary epithelium. This route is a fast as IV bolus ones. Gasses drug such as aerosol (anesthetics) and dispersed form are given via inhalation. It is usually use for respiratory disorder patients( asthma or pulmonary disorder patients) because drug is delivered directly to the site of action without causing systemic side effects. Example: bronchodilator, corticosteroid, albuterol.
- 38. 2:Nasal inhalation: In nasal route drugs are insufflated through the nose either in the form of topical or systemic administration. These are locally acting drugs( such as decongestant for cold and allergy treatment) having minimal systemic effects. Example of such drugs are migraine drugs, nicotine replacement, hormone replacement, desmopressin( for diabetes incipidus) and corticosteroids.
- 41. 3:Intrathecal: It is the administration of drug via injection into the spinal cord or into the subarachnoid space so that it reaches the cerebrospinal fluid and useful in spinal anesthesia, chemotherapy or pain management applications. Use to treat brain tumors.
- 42. It is useful for drugs that fight against certain infections specially post neuro-surgical. These drugs can easily cross the blood brain barrier and specially compounded by the pharmacist or physician because it can not contain any inactive constitutes relative to other drugs given by injections(IV,IM,SC). Sometime it is referred as intrathecal because it means to introduce something into the anatomic space or potential space inside a sheath usually brain and spinal cord arachnoids membrane (under which is the subarachnoid space). Example: Intrathecal immunoglobulin development(for production of antibodies in spinal cord)
- 43. Example: Intrathecal amphoterecin B (to treat cryptococal meningitis) Intrathecal immunoglobulin development (to produce antibodies in spinal cord)
- 44. 4: Topical: It means to apply on the mucous membrane via different dosage forms e.g creams, lotions, gels etc. Usually used when localize affect is require. These are epicutaneous means apply directly to the skin. They can be applied on the tissues other than skin surface such as eye drops( to conjunctiva), ear drops( to ears), or applied to surface of tooth.
- 45. If we strictly say that it has local affect then it can be included in enteral route of medication that has poor absorption in GI. Example: one poorly absorbed antibiotic is vancomycin, which is recommended by mouth as a treatment of Clostridium difficile colitis. Other examples are clotrimazole cream(for skin fungal infection)
- 47. 5:Transdermal: It achieve systemic affect by applying to the skin usually in form of patches. But the rate of absorption is different depending upon the physical characteristic of skin, drug lipid solubility. It is usually used for slow release of drugs such as Nitroglycerine, the antiemetic scopolamine, and anti anginal drug and nicotine transdermal patches( for smoking cessation). In transdermal delivery drug passes through two sub-layers of epidermis to reach into the dermis.
- 48. Stratum cornium is the upper layer of the skin, thickness varies from ten to hundred depending upon the body region. Its composition elements are flattened keratinocytes, surrounded by lipid matrix that is difficult to penetrate. Stratum cornium is the significant barrier for transdermal drug (90%). Below stratum cornium is the viable epidermis. Its thickness is ten times as stratum cornium. But the rate of diffusion is faster here rather than the stratum cornium because it has greater degree of hydration. Below epidermis lies dermis, approximately 1mm thick, 100 times more thick than stratum cornium. It contain vessels that distribute drug into systemic circulation.
- 52. 6:Rectal route: Rectum is the ending portion of large intestine, 15cm long from colon to anal sphincter. It is use for both local and systemic affects. It is non keratinized surface, smaller than the duodenal mucosa. Usually rectum is empty, occupied by few milliliters of fluid ph ranging from 6-8 , and very viscous due to presence of mucin. This characteristics of drug hinders drug absorption since it imposes serious limitations to the drug dissolution process. It is best use for drugs that are destroyed in GIT environment.
- 53. Due to reduce surface area and shorter residence time, the physiochemical characteristics of drug are critical factors. Generally lipophylic drugs are better absorbed than hydrophilic, latter presents slow and incomplete absorption. This route is suitable for solid or liquid dosage form, suppositories, jelly capsule or enemas. Absorption from aqueous and alcoholic solution occur slowly and have great therapeutic effect. For example use of diazepam for suppression of seizures. Suppositories absorption is slow. It depends upon drug formulation, particle size, lipid solubility. Usually water soluble-base suppositories(release by dissolution), low melting point fat bases(melt at body temperature). Sometime contain emulsifying agent to keep drug dissolve in it.
- 55. Thank you!