Route of Drug AdministrationBy Abubakar salisu fago.
Drugs are introduced into the body by several routes. Theymay be taken by mouth (orally); given by injection into a vein(intravenously), into a muscle (intramuscularly), into thespace around the spinal cord (intrathecally), or beneath theskin (subcutaneously); placed under the tongue(sublingually); inserted in the rectum (rectally) or vagina(vaginally); instilled in the eye (by the ocular route); sprayedinto the nose and absorbed through the nasal membranes(nasally); breathed into the lungs, usually through the mouth(by inhalation); applied to the skin (cutaneously) for a local(topical) or bodywide (systemic) effect; or delivered throughthe skin by a patch (transdermally) for a systemic effect. Eachroute has specific purposes, advantages, and disadvantage
Most of the drugs can be given through number of routes.Choice of proper route is depend on factors which are related to patient anddrugs as well.Important factors which govern the choice of route of drug administration area. Physical and chemical properties of drugs ( solid/liquide/gas/stability/PH /irritancyb. Site of desire action- localized and approachable and generalized andnonapproacheablec. Rate and extent of drug absorptiond. Effect of digestive juice and first pass metabolism of drugse. Rapidity at which response is desiredf. Accuracy of dose requiredg. Condition of patients
Grossly we can divide into those fora. Local actionb. Systemic actionLocal routes of drug administrationa. Topicalb. Dipper tissuec. ArterialSystemic routesOralSublingual (S.I) or buccalRectalCutaneousInhalationNasalParenterala. Subcutaneous (S.C) – Dermojet, PelletImplantation, Sialistic (nonbiodegradable)and biodegradableb. I.Mc. I.Vd. Intradermal injection
Local route sThese route can be use for localized lesions at accesiblesites and drugs whose systemic absorption is minimalor absents. Thus higher concentration is attained at thesite of desire without exposing the rest of the body.Topical:Refers to external application of the drug to the surfaceof the body for their localized action. It is moreencouraging and often convenient.Drugs can be efficiently delivered to the localized lesionon the skin, eye, ears, nose, oropharyngeal /nasalmucus, rectum , vagina in the form ofpowder, lotion, ointment, cream, suspension, emulsion,suppositories, logenzegs.Non-absorbable drug can be given orally into the GImucosa eg. Sucralfalte or Vancomycine .
Deeper tissue:Certain deep area can be approach through syringe andneedle but drug should be such that systemic absorptionis slow.Eg. Intra-articular injection (hydrocortisone) or intrathecalinjection ( hydrocortisone)
Intra-Arterial route- Close intra-arterial injectionused for contrast media in angiographyAnti-cancer drug can be infused in femoral or brachialartery to localized the effect for lower limbmalignancy.
Intra-arterial route (IA)The parenteral formulation is injected into anaccessible artery.This route requires specialist training to administertherapeutic agents as if the artery is missed, possibledamage to adjacent nerves may result.The IA route is used to administer radiopaque mediato visualize organs, e.g. heart, kidney.
Intradural and extradural routesIntradural and extradural administration isemployed to achieve spinal anaesthesia. Intradural administration involves injection of thetherapeutic agent within the dural membranesurrounding the spinal cord. Extradural administration involves injection of thetherapeutic agent outside the dural membrane andwithin the spinal caudal canals
Systemic RoutesOralOldest and common mode of drugadministration Safer and more convenient and doesnot need any assistance Noninvasive and often painless Product need not to be sterile so drugsis cheaper Both solid and liquid dosage form canbe administer
Oral route of drug administrationWhat is First pass metabolism?First pass effect
Oral Route of drug administrationLimitationsAction is slow thus not suitable for emergency Unpalatable drugs are difficult to administer(Chloramphenicol) drug may be circumvent with capsule May causes nausea and vomiting Can not be used for noncooperative patients/Unconscious and vomitous patients Absorption of drug is variable Others are destroyed the drug with digestive juice(pen) or in liver (GTN, testosterone, lidocaine)
Sublingual or BuccalThe tablet or pellet containing drugs placed under the tongue orcrushed in mouth and spread over the buccal mucosa.Only lipid soluble non-irritating drugs can be give in this route.Absorption is relatively rapid-action can be produce in a minutesThough it is inconvenient one can spit the drug once the desiredaction of drug obtained.The cheap advantages is liver is by passed thus drugs are protectedfrom fast pass metabolism and drugs are directly into the systemiccirculation.Eg. GTN, desamino oxytocin.
Rectal:Certain irritating and unpleasant drug canbe given through rectal route in the form ofsuppositories or retention enema for theirsystemic effects.•It is rather inconvenient andembracing, absorption is slower, irregularand often unpredictable.•Drug absorbed through externalhaemorrhoidal (50% by passed) andinternal haemorrhoidal veins.Rectal inflammation and leaking can occur.eg.Diazepam, Indomethacine, paraldehyde.
Vaginal Route: Some drugs may be administeredvaginally to women as asolution, tablet, cream, gel, suppository, or ring. Thedrug is slowly absorbed through the vaginal wall. Thisroute is often used to give estrogen to women atmenopause, because the drug helps prevent thinningof the vaginal wall, an effect of menopause (seeMenopause: Hormone Therapy).
Cutaneous:Highly lipid soluble drug can be applied over the skin forslow, constant and prolong absorption. Drugs usually inthe form of ointment , cream, or in the form of speciallydesigned device like transdermal drug delivery system aregiven in this route.> The drug should be highly lipid soluble and non-irritantin nature.> Liver is by passed.>Absorption can be enhanced by rubbing the drugs overthe skin.>Transdermal drug delivery system:
Inhalation:Volatile liquid and gases are given in this routefor their systemic actions. Eg. General anesthesia. Absorption take place from the vast surface ofalveoli- action is very rapid. When administration is discontinued the drug isdefused back into the exhaled air and eliminateand action slowly subside. Thus control administration is possible inmoment to moment by adjustment. Irritant vapor cause inflammation to respiratorytract and cause excessive secretionand may choke the air way.
Nasal Route: If a drug is to be breathed in andabsorbed through the thin mucous membrane thatlines the nasal passages, it must be transformed intotiny droplets in air (atomized). Once absorbed, thedrug enters the bloodstream. Drugs administered bythis route generally work quickly. Some of themirritate the nasal passages. Drugs that can beadministered by the nasal route include nicotine(for smoking cessation), calcitonin (forosteoporosis), sumatriptan (for migraineheadaches), and corticosteroids (forallergies).
Subcutaneous (S.C)The drug is deposited into the loose subcutaneous tissuewhich is richly supplied by nerves (irritant drug can not beinjected) but less vascular ( absorption is slower). Onlysmall volume of drug can be injected through this route.Self injection is possible because deep penetration is notneeded.The route should be avoided to shock patient who arevasoconstricted.Some special forms of these routesa. Dermojetb. Pellet implantationc. Sialistic and biodegradable implants
Dermojet:In this method needle is notneeded, a high velocity jet ofsolution is projected from themicro fine orifice of a gun likeimplements. The solution iscross the superficial layer anddeposited into thesubcutaneous tissue. It isusually painless.
Pellet Implantation:Drug in the form of solid pellet is introduce under the skin with a trocher and cannula. Thisprovides sustained release of drugs over weeks together to few months.Eg. DOCA and testosterone.
A- Intravascular (IV, IA):- placing a drug directly into blood stream.-May be - Intravenous (into a vein) or - intraarterial (into anartery).Advantages1- precise, accurate and immediate onset of action, 100%bioavailability.Disadvantages1- risk of embolism.2- high concentrations attained rapidly leading to greater riskof adverse effects
B-Intramuscular :(into the skeletal muscle).Advantages1- suitable for injection of drug in aqueous solution(rapid action) and drug in suspension or emulsion(sustained release).Disadvantages1- Pain at injection sites for certain drugs.