Dr. RAGHU PRASADA M SMBBS,MDASSISTANT PROFESSORDEPT. OF PHARMACOLOGYSSIMS & RC.

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Enteral routesOralSublingualRectal

Parentral routesIntra venousintra muscularintra peritonialIntrathecalintramedullaryIntra-arterialIntra-articularSubcutaneousIntracardiacEpidural

InhalationalTransdermal

Topical routeConjunctival, nasalAuditory, vaginalUrethralInunctionDermal

1. Commonest, Convenient , Cost effective2. No Skill required, Self medication, Safest,

Sterilization is not required3. Acceptable, Less Adverse effects compared to

parenteral route4. Painless,5. Large volume (doses) can be givenBoth for systemic /local effects in G.I.T (All effects)For local effect e.g. neomycin (an aminoglycoside),

anthelmintics, antiamoebic.

1. Absorption varies (delay, decrease, or increase )2. affected by food or drugs that affect GI motility

e.g. antimuscarinic, opioids )3. Dose may not accurately be delivered4. Irritation of gastric mucosa5. Patient compliance not ensured6. First pass metabolism/Presystemic elimination -

Metabolism of drug (to inactive form) afteradministration before it reaches the systemiccirculation.Greater the first pass effect, lesser will be the

bioavailability

Not suitable for Unconscious patients, Vomitingpatients, Emergency --- (Slow onset of action)Following drugs can not be given by oral route:Drugs destroyed by Stomach pH -benzyl penicillin)Drugs destroyed by Intestinal enzymes (e.g., InsulinHydrophilic drugs which can not absorbed

(e.g. neomycin)Drug interaction: One drug can affect the absorptionof other drug e.g., antacids decrease the absorption of

tetracycline.

Rapid onset of actionUseful in emergency- (glyceryl trinitrate, nifedipine &ergotamine), especially if tablet is crushed, giving greatersurface area for solutionEffect can be terminated by spitting out tabletNo sterilization required, No skill neededFirst pass hepatic metabolism Increase bioavailability

Not affected by gastric acidity or intestinal enzymes

Inconvenient for frequent useIrritation of oral mucosa & excessive salivationPromotes swallowing, so losing the advantage of bypassing the first pass effectPatient compliance not ensuredNot suitable for large doses and vomiting patientsBitter, irritant drugs cannot be given

Can be used for producing both the systemic effectsand local effectsDrugs that are irritant to stomach can be given bysuppository (aminophylline)Suitable in unconscious, vomiting , motion sickness,migraine or when a patient can not swallow, & whencooperation is lacking (sedation in children)

Sterilization is not requiredMinimal skill is requiredAvoid 50% first pass hepatic metabolism (from

lower rectum)For local effect e.g. in proctitis or colitisDemerit-Psychological, patient may be embarrassedIrritation of mucosa & inflammation may occur

with repeated useAbsorption unreliable, especially if rectum is full of

faeces

Rapid onset of actionUseful in emergencyNo first pass effect, 100% bioavailability,Dose more accurately delivered & give effective, &Highly predictable blood concentrationSuitable in vomiting , motion sickness, migraineUnconscious patients, or when a patient can not

swallow & when cooperation is lackingLarge volume (doses) of drug can be given

Costly, Inconvenient, Local irritationMore chances of adverse effects,most dangerousMaximal Sterilization, Skill is requiredSelf-medication is not advisableDrugs that are too irritant(anticancer agents) to be givenby other routes

Chances of local venous thrombosisand infection with prolonged infusion

Reliable and suitable for irritant drugs anddepot preparations (penicillin, neuroleptics,medroxyprogesterone) can be used at monthly

or longer intervalsAbsorption is more rapid than subcutaneous injectionor oral route (soluble preparations are absorbed within10 – 30 mins)

DemeritsInconvenient

Painful especially for frequent useMore chances of adverse effects than oral route

Sterilization is requiredChances of infection are more

Skill required for administrationLocal irritation at site of administration

Not acceptable for self administrationIf any adverse effect occur that can not be

removed.

Can be used for local and systemic effects bothReliable and acceptable for self administration

(e.g. diabetic patients taking Insulin)For local effect --- e.g. local anestheticsPoor absorption in peripheral circulatory failureRepeated injections at one site can cause

lipodystrophy, resulting in erraticabsorption (insulin)

Small amount of drug can be givenSlow absorptionTuberculin syringeExample: BCG vaccine, diagnostic tests,

Allergic sensation testing

Site: Lumen of arteryMerits: Greater concentration of the drug can bedeliveredDemerits: Expertise and asepsis is requiredExamples: Radiopaque contrast for coronaryangiography and cerebral angiography

Site: Subarachanoid spaceMerits: Bypass blood brain barrier and blood CSF barrier-acts directly on meninges and spinal cordDemerits-Asepsis required, expertise is neededPainful and Risky Eg: Radio-opaque contrast media,Xylocaine inj, intrathecal injection of streptomycin in TBEpidural-Through vertebral interspace between dura andlining of spinal canal Eg: Xylocaine injection

Site: Tibial or Sternal bone marrowThe needle is introduced into marrow cavity andeffects are similar to those following intravenousinjection. This route is used when veins are notavailable specially in children.Merit: onset of action very fastDemerits: Strict aseptic conditions,

Expertise and skill requiredPainful and risky

Examples: Bone Marrow transplantation

Site: Injection directly into the joint space Merit: High concentration is obtained in localized area Demerits: sepsis, Joint damage, Pain Examples: Hydrocortisone, Gold chloride for

rheumatoid arthritisIntra Cardiac

In cardiac arrest intra-cardiac injection ofadrenaline is made for resuscitation.

Drugs directly into the nose.Desmopressin is administered intranasally in theTreatment of diabetes insipidusSalmon calcitonin- osteoporosisGnRH analogues

Site-Peritoneal spaceThe peritoneum offers a large absorbing surface areafrom which drugs enter circulation rapidly butprimarily by way of portal vein. Hence First-Pass effectnot avoided.Example: Dialyzing fluid-poisoning and renal failureIn lab animals

Merits-Rapid absorption-large surface areaDemerits-Painful, Risky, Adhesions, Peritonitis

Drugs as gases can be rapidly taken up or eliminatedCan be used for both local & systemic effectsSelf administration is practicableAs gas General anaestheticsAs aerosolβ2 –adrenoceptor agonist bronchodilators

Aerosols & powders provide high localconcentration for action on bronchi, minimizingsystemic effects

Aerosols can also be used for systemic effect, e. gergotamine for migraineAs powder, e.g. sodium chromoglycate

Special apparatus is neededDrug must be nonirritant.If the patient is unconsciousObstructed bronchi (mucus plugs in asthma) maycause therapy to fail

Active ingredient is delivered across theskin for systemic distribution.Example: transdermal scopolamine, transdermalnitroglycerine

Conjunctival, nasal and auditoryEye drops, Ointment, nasal drops, nasal spraysIsotonic aqueous solutions of drugs- sulfacetamide,chloramphenicol, gentamycinAtropine & β-adrenoceptor blocker to eyeVaginal and urethralSolutions, ointments, emulsions, foams, tablets,suppositories and pessaries -Antifungal agentsInunction and dermalRubbing the drug preparation on to the skin, dusting,spraying

MeritsHigh local concentration can be usedwithout systemic effect

Demerit-Systemic effects can occur especially whenthere is tissue destruction e.g., adrenal steroids& neomycin to skinOnly small number of drugs can be used bythis route, Slow onset of action and localreactions can occur

Intravenous 30-60 SecondsIntraosseous 30-60 SecondsEndotracheal 2-3 MinutesInhalation 2-3 MinutesSublingual 3-5 MinutesIntramuscular 10-20 MinutesSubcutaneous 15-30 MinutesRectal 5-30 MinutesIngestion 30-90 MinutesTransdermal (Topical) Variable (Minutes To Hours)

“All substances are poisons;there is none which is not a poison.The right dose differentiates a poison from a remedy.”

Paracelsus (1493-1541)

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