Routes of drug administration

1. Routes of drug administration Siva Nageswara Rao.Mekala Assistant professor, Dept of Clinical Pharmacology.

2. 1 2 3 4 Introduction Each routes with classification Advantages Disadvantages Contents www.themegallery.com

3. Most of the drugs can be administered by different routes. • Drug and patient related factors determine the selection of routes for drug administration. • Factors: 1) characteristics of the drug 2) Emergency /routine use 3) Condition of the patient (unconscious, vomiting ,diarrhoea) 4) Age 5) Sometimes patient’s and doctor’s choice.

6. LOCAL ROUTES • Used for localised lesion at accessible sites • Systemic absorption from these sites is minimal or absent • High concentration is attained at desired site without getting exposed to the rest of the body

7. LOCAL ROUTES TOPICAL • Skin • Epidermis – lipid bilayer • Dermis – readily absorbed • lipid soluble drugs are readily absorbed Causes of systemic toxicity Highly lipid soluble Abraded skin E.g. Ointment, powder Cream, Lotion

8. TOPICAL • Mucous Membranes • Drugs are applied to the mucous membranes of the conjunctiva, nasopharynx, oropharynx, vagina, colon, urethra, and urinary bladder primarily for their local effects.

9. Eye • Local effects usually require absorption of the drug through the cornea; • corneal infection or trauma thus may result in more rapid absorption.

10. Oral cavity: eg: Clotrimazole (oral candidiasis) • GIT : Neomycin –not absorbed from GIT (for sterilization of gut before surgery) • Ear and nose: drops, ointments, sprays etc for infection and allergic conditions. • Vagina: Pessary ,cream or tablet for vaginal candidiasis.

11. Rectum and anal canal: As enema (administration of drug into the rectum in liquid form). • Evacuant enema (for evacuation of bowel) eg. Soap water enema – soap acts as a lubricant and water stimulates the rectum. • Retention enema: e.g.. Methylprednisolone in ulcerative colitis. • As suppository: (administration of the drug in solid form into the rectum)e.g.. bisacodyl (for evacuation of bowel).

12. Bronchi : As inhalation eg: salbutamol , ipratropium bromide etc for bronchial asthma and COPD. www.themegallery.com

13. INTRA ARTICULAR(deeper) tissues) • Here drugs are injected directly into joint space for the treatment of local conditions • Eg: Hydrocortisone acetate in the treatment of rheumatoid arthritis. infiltration anesthesia with local anesthetics.-Lignocaine Repeated administration may cause damage to the articular cartilage.

14. Systemic routes • Drugs administered by this route enters the blood and produce systemic effect. • Enteral – directly into the GI tract • Oral • Rectal • Sublingual • Parenteral • Intravenous • Intramuscular • Intraperitoneal • Subcutaneous • Intra arterial • Intrathecal - Inhalation

15. ORAL (ENTERAL) • Oral ingestion is the most common method and acceptable route for drug administration. Advantages: • Safer • Painless • Cheaper • Convenient for repeated and prolonged use • Can be self administered.

16. Disadvantages to the oral route : • Oral route has a slow onset of action. Not suitable for/in: • Unpalatable and highly irritant drugs • Unabsorbable drugs (aminoglycosides) • Drugs that are destroyed by digestive juices (adrenaline) • Drugs with extensive first-pass metabolism (lignocaine) • Unconscious patients • Uncooperative and unreliable patients • Patients with severe vomiting and diarrhoea.

17. Not absorbed via oral route Drugs which are • Highly polar e.g. streptomycin • Being quaternary salts – e.g. d-tubocurarine • Destroyed by digestive juices- e.g. penicicilin-G ,Insulin, oxytocin • Having high first pass metabolism e.g. morphine, isoprenaline

18. Enteric coated tablets: • Enteric-coated tablets: • cellulose, acetate, kerarin etc. • Used to prevent gastric irritation, protect the drug from gastric acid and retard the absorption of the drug thereby prolonging its duration of action. Eg Diclofen,Dynasprin encotabs

19. Sustained-or time release preparations: • These preparations consists of drug practical's, which have different coatings that dissolve at different intervals of time. • Uses: 1) prolongs the duration of action of the drug 2) Reduces the frequency of drug administration 3) Improves patient compliance. Eg: Nifedipine (For Hypertension) Pyridostigmine( For myasthenia gravis) Diclophenac www.themegallery.com

20. RECTAL ADMINISTRATION. The rectal route often is useful when oral ingestion is precluded because • the patient is unconscious • when vomiting is there Approx. 50% of the drug bypass the liver However, rectal absorption often is irregular and incomplete, and many drugs can cause irritation of the rectal mucosa e.g. Diazepam in children with status epilepticus

21. SUBLINGUAL ADMINISTRATION: • A tablet is placed under tongue and allowed to dissolve in mouth or crushed • Active substance gets absorbed through buccal mucous membrane directly into circulation

22. Advantages • Self medication, • rapid onset, • quick termination and • high bioavailability • direct absorption into circulation- bypasses liver • Safe and convenient • Action can be terminated by spitting out the tablet. www.themegallery.com

23. For example, nitroglycerin is effective when retained sublingually because it is nonionic and has very high lipid solubility. Thus, the drug is absorbed very rapidly. • Nitroglycerin also is very potent; relatively few molecules need to be absorbed to produce the therapeutic effect.(Acute anginal attack) • Other examples are Nifedipine, Ondansetron, Domperidone, isoprenaline, methyl testosterone, clonidine etc.

24. PARENTERAL INJECTIONS • Routes of administration other than enteral are called parenteral.(par – beyond, enteral –intestinal) • Advantages • Rapid onset and suitable for emergency • Unconscious, uncooperative and unreliable patients • The presence of vomiting • Suitable for irritant drugs High first pass metabolism not absorbed orally destroyed by digestive juices.

25. Disadvantages: • Require sterilization and aseptic conditions • Are expensive • Self medication is not possible • Causes local tissue injury to nerves , vessels etc. www.themegallery.com

26. INJECTIONS • The major injectible routes are intravenous subcutaneous intramuscular.

28. INTRAVENOUS: Drugs are injected directly into the blood stream through vein . Produces rapid action A drug can be injected as • Bolus (single ,relatively large dose of a drug injected rapidly or slowly as a single unit into a vain E.g. Streptokinase immediately after MI • Slow intravenous- e.g., aminophylline ,morphine • Intravenous Infusion (adding the drug to a bottle containing dextrose/saline) - dopamine infusion in cardiogenic shock.

29. ADVANTAGES: • Bioavailability is 100% • Quick onset of action , so it is the route of choice in emergency Eg: I.v diazepam for status epilepticus • Large volume can be given Eg: I.v fluid in case of severe dehydration. • Highly Irritant drugs can be given Eg: anticancer drugs • Can be titrated with response • Can be given, if the patient is unconscious, uncooperative

30. DISADVANTAGES: • Self medication not possible ii. Asepsis required iii. Once the drug injected, its action cannot be halted Iv .Extravasations can cause injury and sloughing of surrounding tissue www.themegallery.com

31. Precautions. • Drug should usually be injected slowly. • Before injecting ,make sure that the tip of the needle is in the vein. www.themegallery.com

32. SUBCUTANEOUS: Injection of a drug into a subcutaneous site • Only non irritant drugs are preferred • The rate of absorption following subcutaneous injection of a drug often is sufficiently constant and slow to provide a sustained effect. E.g., insulin , Adrenaline. • The incorporation of a vasoconstrictor agent in a solution of a drug to be injected subcutaneously also retards absorption. E.g., lidocaine and epinephrine

34. Advantages: • Self administration is possible Eg: Insulin Disadvantages: • Suitable only for non irritant drugs • Drug absorption is slower, hence not suitable for emergency. www.themegallery.com

35. PELLET IMPLANTATION: Drugs are implanted under the skin in a solid pellet form and absorption occurs slowly over a period of weeks or months e.g., testosterone • DERMOJET: High velocity jet of drug solution is projected from a micro fine orifice into subcutaneous space e.g., mass inoculations • IMPLANTS: Drugs packed in tubes and capsules are implanted under the skin. Non-biodegradable are to be removed and not the biodegradable one e.g., Norplant (levonorgestrel )

36. INTRAMUSCULAR • The drug is injected into deltoid muscle or gluteus muscle of buttock • Alternative area is vastus muscle underlying lateral surface of leg in children • 5-10 ml of drug can be given at a time • Mild irritant, and colloids can be injected • Self administration not possible, can injure nearby nerves, painful and may cause abscess. • E.g., antibiotics, antiemetic

37. INTRAARTERIAL: • This route is rarely employed. • Drug is injected directly into an artery to localize its effect in a particular tissue or organ e.g., anticancer like nitrogen mustard • Diagnostic agents sometimes are administered by this route (e.g., coronary angiography) • Intraarterial injection requires great care and should be reserved for experts.

38. INTRATHECAL: Drugs are injected directly into the spinal subarachnoid space e.g., Spinal anesthetics lignocaine Antibiotics – amphotericin B, given for systemic mycosis

39. INTRADERMAL • The drug is injected into layers of skin raising a bleb e.g., BCG vaccine • Small amount of this drug is given • Employed for testing drug sensitivity • Small pox vaccine

40. INHALATION Drugs are given by the • Metered dose inhalers • Dry powder inhalers • Nebulizers • Gases - general anesthetics drugs by this route produce rapid effects

43. Nasal sprays: Drug is absorbed through the nasal mucosa to provide a therapeutic effect. Such absorption takes place through mucosa overlying nasal-associated lymphoid tissue. Some peptide hormone analogues given as nasal sprays are • antidiuretic hormone • gonadotrophin-releasing hormone • calcitonin • sumatriptan These peptides are inactive when given orally as they are quickly destroyed in the gastrointestinal tract

44. SPECIAL DRUG DELIVERY SYSTEMS • These incorporate drugs in a dosage forms that release the medication - At predetermined site • At predetermined rate • Over an extended period of time from a single application

45. OCUSERTS: • Thin elliptical micro units • contain drug in a reservoir • drug is slowly released through a membrane by diffusion at a steady state • e.g., Pilocarpine ocuserts are used in glaucoma. • Placed under lower eyelid to deliver pilocarpine for a period of 7 days following a single application.

46. Transdermal: Adhesive patches which deliver drug at a constant rate into systemic circulation • By this route drug is delivered at a constant and predictable rate • Also these preparations provide smooth and steady plasma concentrations for a period of 1-3 days • The sites of application are chest, abdomen, upper arm, lower back, buttocks, mastoid.

47. Controlled-release topical patches have become increasingly available. Examples include nicotine for tobacco-smoking withdrawal scopolamine for motion sickness nitroglycerin for angina pectoris testosterone and estrogen for replacement therapy

48. Transdermal route (Adhesive patches): • Drug is administered in the form of patch (Varies from 5-10square cms)

50. Advantages: • Self administration is possible • Patient compliance is better • Duration of action is prolonged • Systemic side effects are reduced • Provides a constant plasma concentration of the drug Disadvantages: • Expensive • Local irritation may cause dermatitis and itching • Patch may fall off unnoticed. www.themegallery.com