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مختبر ادوية عملي

Routes of drug administration

Factors to be considered when choosing certain route:

1. Site of drug action: e.g., treatment of certain GIT diseases necessitates giving the drug orally.

2. Drug nature: intravenous fluids should be isotonic.

3. Onset of action: treatment of emergency conditions necessitates the use of intravenous route.

4. Duration of action: drugs intended for longer duration of action are given by a route when absorption is slow.

5. Patient status: oral route can not be used when the patient is unconscious, or has difficulty in swallowing, or has repeated vomiting.

6. Desire of the patient.

Routes of administration can be classified as follows:

A. Enteral (GIT): oral, sublingual, and rectal.

B. Paranteral: IM, IV, ID, SC, inhalation, topical, and others

Enteral:

1. Oral: the most common route. Ideally swallowing a solid dosage form should be followed by drinking 150 ml of water while the patient in standing position.

Advantages:

a) Simple, convenient, and acceptable.

b) Oral drugs can be given in different dosage forms.

c) Safe route: since in overdose, it can be managed easily.

Disadvantages:

a) Some drugs are destroyed in the gut (e.g., some penicillins, insulin, oxytocin)

b) Some drugs may cause gastric irritation.

c) Absorption may be affected by food or by other drugs which inhibit gut motility e.g., antimuscarinics and opiods.

d) First pass metabolism (by intestinal wall and by the liver) limits the efficacy of some drugs when taken orally.

2. Sublingual: (for systemic effect)

Advantages:

a. Rapid effect.

b. Avoid first pass metabolism

Disadvantages:

a) Irritation of the mucous membrane of mouth if used frequently.

b) Excess salivation may promote swallowing.

3. Rectal:

Advantages:

• Suitable in patients with vomiting, who cannot swallow, or in children.

• Can be used for local effect to avoid systemic side effects.

Disadvantages:

• Rectal inflammation may occur with repeated use.

• Absorption can be unreliable especially if the rectum is full of feces.

Paranteral

Advantages:

1- Used for drugs that are poorly absorbed from the GI tract and for drugs that are unstaible in GIT (insulin).

2- Used when the patient is unconcious or when rapid onset of action is required (IV).

Disadvantages

• The injected drug can not be recalled simply in case of toxicity.

1. Intravenous route:

(drugs should be given slowly)

Advantages:

• Large volumes can be given via this route.

• Rapid onset of action.

• Suitable for continuous infusion (for rapidly destroid drugs)

• Suitable for too irritant drugs (anticancer drugs).

• No first pass metablism.

Disadvantages:

• IV fluid should be aqueous, and (isotonic)

• Infection and local venous thrombosis.

1. Intramuscular injection (IM):

• Common route, more rapid than subcutaneous route, and less affected by peripheral circulatory failure.

• Isotonicity is not essential except for the comfort of the patient.

• Absorption is more rapid than subcutaneous route

• Drug can be aqueous or specialized depot preparations.

• Sites of injection: gluteal region, upper arm, upper lateral thigh.

Disadvantages:

• Not acceptable for self administration

• May be painful

2. Subcutaneous route (SC):

• Injection (1ml or less) or Mechanical pumps (insulin)

• The solution to be injected should be aqueous

• Poor absorption in case of peripheral circulatory failure

• Reliable and acceptable for self-administration.

Disadvantages

This route should not be used with drugs that cause tissue irritation, because severe pain and necrosis may occur

Others:

Intraperitoneal:

• Relatively large volume of non-irritant drugs

• Absorption is faster than IM or SC

Intraderaml:

• The volume of preparation injected is rarely more than 0.2 ml because the tissue volume is small and compact.

• Absorption is slow due to poor circulation

• The isotonicity is very important because the route is mostly for diagnostic purposes and non-isotonic solutions may cause false signs, which gives false positive results.

Topical (local application):for local or systemic effects: skin, eye, ear, nose, lung, etc…

• For local or systemic effects

• High local concentration with low systemic effects, BUT,...

• Systemic absorption can occur especially when there is damaged tissue.

Inhalation:

• The drug is taken through the inspired air (gas, or aerosol)

• Rapid absorption (wide surface area) with rapid effect almost as rapid as IV route.

• Close control of the dose

• Self administration

• Particularly effective for respiratory disorders because the drug is delivered directly at the site of action and systemic SE are minimized

Disadvantages:

• Need special aparatus

• Should not be irritant if the patient is concious

Other routes:

• Intrathecal/ intraventricular: Used to deliver the drug directly into the CSF

• Intracardiac

• Intragingival

• intraarterial

• Intraosseous

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