Routes of Drug Adminstration PDF

Dr. Nada Ibrahim Elshiekh  A route of drug administration is the way by which a drug is delivered into the body.  The choice of the route of drug administration depends up on Factors  1- Physical characteristics of the drug: EDTA is a chelating agent not absorbed orally (from GI...

Dr. Nada Ibrahim Elshiekh  A route of drug administration is the way by which a drug is delivered into the body.  The choice of the route of drug administration depends up on Factors  1- Physical characteristics of the drug: EDTA is a chelating agent not absorbed orally (from GIT). It must be given by I.V injection during treatment of heavy metal poisoning  2- Rapidity of response (Rapidity is required for the response): The ↑ the rate of drug absorption→→→→↑ in the rapidity of response. I.V. and Inhalation routes →→→→ rapid response. S.C. and implantation →→→→ slow response.  3-The rate of the drug release: S.C and Implantation →→→→ slow release of the drug.  4- The first hepatic effect (metabolism): Nitroglycerine is given sublingually (rapid onset) →→→→ by pass the first hepatic metabolism (short duration of action).  5-The nature and location of the disease.  6-The condition of the patient (conscious or unconscious).  7-The purpose of medication: Magnesium sulphate orally is purgative but I.V. or S.C. is CNS depressant and muscle relaxant. A) Body orifices B) Parental C) Topical 1.Orally 1.Intravenous (I.V) 2. Intramuscular(I.M) 2. Rectal 3. Subcutaneous(S.C) 3. Nasal route 4. Intradermal (I.d) 5. Intraperitoneal (I.P) 4. Vaginal route 6. Intracardiac 5. Urethral route 7. Intra-articular 6.Intramammary 8. Epidural 9. Intra-arterial 10. Intrathecal Enteral Parenteral Others The drug enters the This pathway -Topical or body through GIT usually allows drug percutaneous openings. to be delivered application directly to target -Inhalation -oral tissue. -Sublingual -Injection -Rectal -infusion  1-Oral Route (Per os or per mouth or orally) Advantages Disadvantages 1- Most common route  1- Sometimes inefficient - only part of theof Administration. drug may be absorbed. 2- Safe.  2 - First-pass effect - drugs absorbed 3- Economic.  orally.  3- Slow onset of action due to slow absorption (up to 48 hours in ruminants),so it is Unsuitable in emergency.  4- Irritation to gastric mucosa - nausea and vomiting and even gastric ulceration.  5- Unsuitable in unconscious animals.  6- Unsuitable in the presence of gastrointestinal disturbances e.g vomition ordiarrhea.  7- Destruction of drugs by gastric acid and digestive juices and enzymes (Insulin , Natural Penicillins and pituitary hormones ).  8- Unpleasant taste of some drugs, Need good handling of the animal.  9- The presence of food in the GIT interferes with the absorption of some drugs due to formation of non absorbable food-drug complex as tetracyclines and milk or dairy products.  10- The presence of other drugs may interfere with the absorption of some drugs (drug - drug interaction).  The drug should be: Medications given by this  palatable, route may be placed directly  nonirritant, in the mouth or given by a  stable at the pH tube passed through the of the intestinal tract, mouth.  unaffected by digestive juice and should be adequately absorbed if it is intended to produce a systemic effect.  Some drugs are taken as smaller tablets which are held in the mouth (between buccal and gingival mucosa) or under the tongue. Advantages Disadvantages 1- rapid absorption →→→ rapid 1-Not suitable for administration onset of action. of large volume of drug (Only 2- drug stability (not destroyed by small doses). gastric juice) 2-Unpleasant taste of some drugs. 3- avoid first-pass effect (enter the 3-Not suitable for administration systemic circulation directly and of drugs. of low lipid solubility. not enter the portal circulation). 4-Irritation of oral mucosa.  Mostly enemas or suppositories.  Maybe used for local effect (drugs that are not absorbed) or systemic effect(drugs that are absorbed).  This route can be used for drugs that can be readily absorbed from the rectal mucosa. Advantages Disadvantages 1.It avoid disadvantages of 1- Many drugs may cause oral route. irritation of rectal mucosa. 2.It is suitable for 2- Slow and uncertain unconscious animal. absorption of drugs. 3.It is suitable if patient is nauseous or vomiting 4.good for drugs affecting the bowel such as laxatives.  The word parenteral is derived from two Greek words Para=beside and enteral from intron = intestine.  1- Injections routes: A- Intravenous B- Intra-arterial C- Intramuscular D- Subcutaenous E- Intradermal F- Intraperitoneal G- Intrathecal H- Epidural I-Intracardiac J- Intra-articular  Intravenous injection or (IV injection ) is the giving of substances directly into a vein.  This route is made by inserting the needle into superficial veins.  Drugs given by this route produce the most rapid onset of action accompanied by the shortest duration.  The injected drug must be in an aqueous solutions.  The irritant drugs must be injected slowly and diluted.  The injected drug must be miscible and inert to the blood.  Intravenous medication should be administered slowly to avoid toxic or allergic reactions. Large ruminants, Dogs and cats Birds Rabbits small ruminants and equine  Jugular vein. Recurrent tarsal Wing vein. Ear vein. vein (hind limb) Cephalic vein in (Fore limb).  1.IV can deliver continuous medication, e.g., morphine for patients in continuous pain, or saline drip for people needing fluids.  2.100% bioavailability ( IV ).  3.suitable for unconscious animals.  4.The best route in an emergency case.  5.Avoid all disadvantages of oral route (First pass effect & destruction of drugs by gastric acid and juice).  6.More accurate dose.  1.Induction of phlebitis or abscess at the site of action due to local irritation.  2.Increased incidence of embolism.  3.Erythrocytic agglutination or hemolysis may be occurred due to injection of hypotonic or hypertonic solutions.  4.Not suitable for insoluble preparations.  5.Expensive.  6.Need application of strict hygienic measures.  7.The drug can not be recalled (High risk).  8.Increasing the adverse effects due to increasing the absorption.  In this route the drugs are injected directly into the artery (within artery).  It increased drug delivery to the area  Localization of effect in particular tissue or organ.  It is mainly used for cancer chemotherapy. Liver tumors, head & neck cancers.  Diagnostics agents.  In this route the drugs are injected directly deeply into the skeletal muscles (usually gluteal and upper thigh muscles) in most animals species.  The intramuscular route of administration produces a slower onset of action than the intravenous route but usually a longer duration of action.  The onset of action can be relatively fasten with a water- base form (aqueous ) or slower with other diluents (vehicle) such as oil.  As muscles are less sensitive to pain, hence are more suitable for injecting moderately irritant drugs.  1.Very rapid absorption of drugs in aqueous solution (slower but longer than IV route).  2.Used for oily preparation or drugs on suspension  3.Repository and slow release preparations.  4.Suitable for administration of moderately large volumes of drugs.  1.Pain at injection sites for certain drugs.  2.It may result in abscess formation at the site of injection due to local irritation.  3.Absorption is sometimes erratic, especially for poorly soluble drugs, e.g. diazepam, phenytoin.  4.The solvent maybe absorbed faster than the drug causing precipitation of the drug at the site of injection.  1.In this route the drugs are injected under the skin.  2.It is used when a slow and continuous absorption of drugs is needed.  3.It is suitable only for non irritating drugs.(Irritant or hyper- osmotic solutions should not be given by this route.)  4- The absorption rate following SC injection can be more delayed by:  a-Incorporation of vasoconstrictor agent in drug solution.  b-Application of tourniquet adjacent to the site of injection.  c-Implantation of drugs in the form of solid pellets under the skin.  Advantages Disadvantages 1.Rate of absorption slow 1.Pain, necrosis and and sustained. tissue sloughing. 2.Suitable for insoluble 2.It is suitable only for non irritating suspension and solid pellet drugs(isotonic solution) implantations. 3.It is suitable for administration of relatively large volumes of saline and glucose solution  1- Drug is injected into the skin.  2- It is used in diagnostic tests as Tuberculin test.  3- Testing drug sensitivity (Penicillins).  4- Anesthesia  1.It is the injection of a substance into the peritoneum (body cavity).  2.IP injection is more often applied to animals (more common in experimental animals than humans).  3.It is generally preferred when large amounts of blood replacement fluids are needed, or when low blood pressure or other problems prevent the use of a suitable blood vessel for intravenous injection.  Advantages Disadvantages 1.Rate of absorption is rapid due 1-It may result in peritoneal to great surface for adhesion. absorption→→ rapid onset of 2-It may result in peritonitis action. at the site of injection. 2.The ease of administration 3- Danger of infection. compared with other parenteral methods. 3.It is suitable for administration of large volumes of drugs and blood replacement fluids when IV injection is difficult.  It is an injection into the spinal canal (intrathecal space surrounding the spinal cord), as in spinal anaesthesia or in chemotherapy or pain management applications.  This route is also used for some infections, particularly post-neurosurgical.  1.The bioavailability to CNS is 100%.  2.The drug needs to be given this way to avoid the blood brain barrier.  3.It is suitable for treatment of serious CNS infections (meningitis and brain tumors).  Injection or infusion into the epidural space, e.g. epidural anesthesia. (The epidural space is outside the dura mater (meninges) but inside the spinal canal.  The drug is injected around the nerves come out of the spinal canal to the various parts of the body.  It is used for epidural anaesthesia during labor, uterine and vaginal prolapse.  Selecting the injection site, the first movable saccro-coccygeal space, by moving the tail up and down and feeling for a depression  intrathecal epidural is an injection of narcotics is an injection or infusion of (and sometimes small local anesthetic/narcotic amounts of local anesthetics) mixture into the epidural into the spinal fluid, which is space, where the nerves come in direct contact with the out of the spinal canal to the spinal cord. various parts of the body.  1.The drug is injected directly into the heart muscles or ventricles.  2.They are used in emergencies.  3.The two primary complications are injury to the coronary artery and haemorrage within the pericardium.  1.The drug is injected directly into the joint capsule.  2.is a procedure used in the treatment of inflammatory joint conditions, such as rheumatoid arthritis, goutt, tendinitis, bursitis and occasionally osteoarthritis.  3.This route needs strict sterility measures.  1.The drug is injected directly within the udder.  2.Intramammary infusions are an important part of mastitis treatment and control.  3.Proper aseptic infusion procedures are necessary to maximize treatment effectiveness and prevent contamination of the quarter being infused.  4.The udder must be completely evacuated prior to drug infusion.  Applied to  a- Inhalation  b-Skin  c- Mucous membranes Nasal Eyes Vaginal  Gaseous and volatile agents and aerosols.  Rapid onset of action due to rapid access to circulation: a. Large surface area. b.Thin membranes separates alveoli from circulation. c. High blood flow.  Avoids hepatic first-pass loss  Local application at the desired site of action in pulmonary disease  Treatment of bronchial asthma.  It may results in pulmonary irritation.  1-Dermal: rubbing in of oil or ointment (local effect )  Usually used for local effect  Ideal →→ no skin penetration, systemic absorption  Large variation in absorption due to: -Blood supply -No of hair follicles -Skin damage -Hydration Properties of drug -vehicle  Absorption of drug through skin (systemic action).  Delivery of drug to bloodstream via skin.  Small lipid soluble drugs more readily absorbed.  It is characterized by: -stable blood levels. -no first pass metabolism. i- Nasal (Intranasal): ii- Eyes (Intraocular): iii- Vaginal(Intravaginal): It is usually used for Used for local Used for local local effects. effects, usually in the effect. The used drug form of drops, Systemic preparations are ointments, lotions absorption may be drops, oint. or cream. Drug crosses cornea occurred. Drugs are well and enters aqueous Pessaries, creams, absorbed from nasal humor distributes to gels, douches. mucosa into systemic other parts of the circulation. eye. Prolonged effect – with gels, ointments.  Intravenous →→→ 30-60 seconds  Intramuscular →→→ 10-20 minutes  Subcutaneous →→→ 15-30 minutes  Rectal →→→ →→→ 5-30 minutes  Ingestion →→→ →→ 30-90 minutes  Sublingual →→→ 3-5 minutes  Inhalation →→→→ 2-3 minutes  Transdermal (topical) →→→ variable (minutes to hours)