Injections - parenteral Flashcards

1
Q

What are the types of injections?

A

a drug is given by a route which takes it directly into body fluids, thus by-passing the preliminary process of passage across GI membranes
- directly into systemic circulation

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2
Q

What is an injection?

A

Intravenous = most common
Intramuscular
Intradermal (subcutaneous)
Intra-arterial
Intracardiac
CNS injections (intraspinal, intra-ventricular, etc.)Intra-articular
Ophtalmic injections (subconjunctival, intra-vitreal, etc.)

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3
Q
Where are the following injections inserted into?
intradermal
subcutaneous
intravenous
intramuscular
A
intradermal
- into the dermis = skin layer under the epidermis (upper skin layer) 
subcutaneous
- into the subcutaneous tissue = tissue layer between the skin and muscle 
intravenous = most common
- into a vein
intramuscular 
- into a muscle
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4
Q

What happens during an iv injection?

A

it is a bolus injection

  • injected all at once
  • concentration peaks very quickly = reaches maximum
  • decreases = excretion, metabolism, distribution
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5
Q

What is the drip between a drip and repeated injections?

A

both are used for sustained release of drugs

drip

  • given at a steady rate over time
  • concentration increases until it plateaus in the desired level

repeated injections
- repeatedly injected when concentration levels fall below the specific therapeutic window

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6
Q

What are the employed types of iv formulations? What formulations should not be used?

A

employed types

  • aqueous solutions
  • oil in water emulsions

must not be used

  • water in oil emulsions = not compatible with blood (70% water)
  • suspensions = drugs are not fully dissolved and can clog/block the veins
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7
Q

What are the advantages of iv injections?

A

quick onset of action
- useful for when fast therapeutic responses are required

first pass metabolism is by-passed
- avoids liver metabolism

bioavailability
- 1 = entire available dose is administered and used

patient cooperation is unnecessary
- useful for unconscious patients, patient adherence is not a factor

allows precise dosing at a controllable rate
- can maintain the drug in a therapeutic level

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8
Q

What are the disadvantages of iv injections?

A

self administration is less likely so trained staff is required

drug is irretrievable
- in the case of an overdose, it cannot be retrieved

possibility of an overdose

injection site reaction

compliance
- low

sterility

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9
Q

What is the therapeutic window?

A

concentration range in which drug levels have the best effects
- must be sustained in this level

too high = toxicity
too low = ineffective treatment

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10
Q

What is the ideal treatment for persistent pain? When should iv and im injections be used?

A

breakthrough medication which can be used along side around the clock (regular) medication is ideal
- can cover the spikes of painful events that break through the regular drug treatment

iv injections are best for break throughs in pain
- fast onset of action

im injections are best for chronic pain/painful events over prolonged time

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11
Q

What are factors affecting the rate of drug absorption from the muscle?

A
blood supply to the muscle 
massage 
- can increase blood supply
ionisation of drug
type of formulation
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12
Q

What are the types of formulation for im injections?

A

aqueous solutions
suspensions in aqueous vehicle
suspensions in oily vehicle
- take time for drugs to diffuse through the muscle into the blood therefore the drugs will not clot blood vessels

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13
Q

Where are drugs inserted into? What are their properties?

A

site of injection is a critical factor in determining the absorption rate since different muscles have different degrees of vascularity

arm - deltoid
- most rapid absorption due to greatest vascularity

thigh - vastus lateralis
- second most rapid absorption

buttocks - gluteus maximus

  • least rapid absorption
  • lowest vascularity = poor circulation
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14
Q

What can facilitate absorption and spreading of drugs in im injections?

A

heat or massage can increase blood supply

addition of the enzyme hyaluronidase to the preparation facilitates the spreading of the drug in the muscle
- alters permeability of the connective tissue through the hydrolysis of the hyaluronic acid

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15
Q

What are the features of im injections?

A

allows delivery of exact amounts of drug whilst allowing site control over the rate of absorption

compared to iv
- it has slower onset, slower excretion leading to prolonged time in the bloodstream

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16
Q

What are the features of subcutaneous injections?

A

subcutaneous tissue is less vascularised than muscle tissue
- drugs are absorbed more slowly and the effects are prolonged

route is only suitable for small dose volumes

more painful than intramuscular due to greater number of nerves

high potency drugs are often given by this route due to the low amounts required (e.g. steroids)

17
Q

What are the routes of administration for subcutaneous injections?

A

drug injected into alveolar connective tissue just below skin surface

  • absorption slower than I.M. route generally
  • spreads action across several hours to avoid too intense / short / frequent use
18
Q

What are the different vehicle formulations? What are their properties?

A

water

  • high chemical purity
  • pyrogens free = free of substances that cause fevers
  • can only be prepared by distillation

sterilised water

  • used to dissolve or dilute parenterals before use
  • pyrogen free
19
Q

How can water be purified?

A

distillation of potable water

suitable pre-treatment required

  • chemical softening and filtration
  • deionization and pH adjustment
  • followed by reverse osmosis and distillation
20
Q

What are non-aqueous solvents? When are they used? What is their role?

A

water miscible co-solvents
- glycerin, propylene glycol (PEG)

  • used in small-volume injectables
  • for use via IM route

increase solubility in water
stabilize drugs degraded by hydrolysis

21
Q

What are the different types of additives? What is their purpose? What are their properties?

A

anti-microbial agents

  • excipients used to prevent the growth of bacteria
  • are used in multiple dose vials = to prevent contamination as multiple doses are taken
  • stable and effective in the free form at low concentrations
  • may interact with other components (including packaging –rubber cap)

anti-oxidants

  • prevent degradation of the active ingredient
  • have a lower oxidation potential than the active ingredient = oxidised preferentially
  • butylated hydroxy toluene

chelators
- remove traces of metals
= metals catalyse oxidative degradation

buffers
- ideal pH of parenteral products is 7.4