Routes of Drug Administration PDF

Faculty of Pharmacy Topic 6: Routes of Drug Administration Systemic and local administration: Systemic administration means that drug enters the blood stream distributing throughout the body and produces systemic effects. While local administration is the s...

Faculty of Pharmacy Topic 6: Routes of Drug Administration Systemic and local administration: Systemic administration means that drug enters the blood stream distributing throughout the body and produces systemic effects. While local administration is the simplest mode of administration; drug is applied to the site where the desired action is required (lower side effects). Classification of routes of drug administration: Systemic Local Enteral Parenteral Skin Topical Oral Inhalation Intranasal Sublingual Transdermal Eye drops Transdermal Buccal Injection Inhalational Rectal Others 1  Faculty of Pharmacy Enteral routes Routes where the drugs administered via: Oral routes Sublingual routes Buccal routes Rectal routes Drug 2  Faculty of Pharmacy Oral route Most drugs can be administered orally for systemic effect mainly. Drug is in the form of solid (tablets & capsules) or liquid (solutions & suspensions). Absorption may begin in mouth and stomach. However, most drugs are usually absorbed from small intestine to blood circulation. Advantages of oral route Most commonly used method Safe, convenient, and painless method Self- administration of drugs and easy to administer. Less expensive Disadvantages of oral route: Slower onset of action. Presence of food in GIT can affect drug Not suitable with: absorption: - Acid sensitive drugs - Absorption of tetracyclines is slower “Penicillin-G” with milk products “calcium” - Unconscious and First-pass metabolism (First-pass effect, uncooperative patients presystemic metabolism): the drug - Emesis and diarrhea concentration when administered orally, Bad taste and smell of is greatly reduced before it reaches the some drugs systemic circulation. 3  Faculty of Pharmacy First pass effect (First-pass metabolism, presystemic metabolism) The drug gets metabolized at a specific location in the body (mainly in liver), resulting in reduced drug concentration before reaching systemic circulation. 4  Faculty of Pharmacy Sublingual and buccal routes: They are two different ways of giving drug by mouth. Both sublingual and buccal drugs come in tablets or films. Sublingual route Buccal route It involves placing a drug under the tongue It involves placing a drug between (Sublingual cavity) to dissolve the gums and cheek to dissolve and then drug absorbed into blood. and then drug absorbed into blood. Advantages of Sublingual and buccal Disadvantages of Sublingual and routes buccal routes v The cheek and sublingual cavity have Not applicable with unpleasant many blood capillaries, So, taste & odor Generate excessive production of o Drugs absorbed directly into the saliva bloodstream Prevent the patient from eating, or drinking during administration o Rapid onset Due to small size of oral cavity, o Avoid digestive system (enzymes, only potent drugs can be acid, food) delivered (Small doses) o Bypass first pass effect. Irritation of the mucous v If patients have trouble swallowing membrane medication v Action can be terminated by spitting out medicine. 5  Faculty of Pharmacy Sublingual route Buccal route Example: Example: Glyceryl trinitrate Fentanyl (analgesic). (GTN) for angina Rectal route It involves administration of drugs in the rectum. Rectum's wall is thin and rich in blood vessels, so, the drug is readily absorbed and distributed to the body. 6  Faculty of Pharmacy Rectal drugs may be: ♦ Solid dosage forms: such as Suppositories ♦ Liquid dosage forms: such as Enema Enemas: treat constipation by introducing fluids into the intestines through the rectum. The liquid softens the stool, while the enema nozzle loosens the rectum, stimulating the bowel movement. Retention enema: It is used to diagnose the pathology of lower intestine. Rectal drug administration for: A) Local effect on rectal conditions such as glycerin suppositories (laxative). B) Systemic effects such as Cetal and Dolphin suppositories (antipyretic & analgesic) Advantages of rectal route Useful in unconscious or uncooperative patients. Useful in patients with nausea or vomiting Drug cannot be destroyed by enzymes. Preferred if drug is gastric irritant. Disadvantages of rectal route Chances of rectal inflammation. irregular & unpredictable Absorption Inconvenient & not acceptable by patients. Some of the drug absorbed from upper rectum can be subject to the first pass effect, bioavailability therefore, may be less than 100% 7