Parenteral administration

Question 1

Main routes of administration

Answer 1

IV-Rapid response, Large/small vol, solutions/emulsions, disperse phase <1micrometre

IM- rapid absorption, small vol, can be used for controlled release

SC- slow onset, vol around 1ml, can be used for implants, preferred route for insulin

Question 2

Disadvantages of parenteral

Answer 2

Allergies are rapid and intense
Cannot reverse effects easily
More expensive due to asceptic technique
Pain due to needles 
Skill needed to administer

Question 3

General requirements for parenterals

Answer 3

Must be sterile
Free from endotoxins/pyrogens
Free from visible particulates
Suspensions can’t be given IV and droplet size must be <3micrometre

Question 4

Common excipients

Answer 4

Co solvents- Glycerol, ethanol, propylene glycol

Surfactants- Tween series (non ionic surface acting)

Buffers-Acetate, citrate or phosphate salts to maintain pH

Question 5

Common excipients cont.

Answer 5

Tonicity- NaCl, dextrose

Preservatives- benzalkonium chloride, benzoic acid, cresol

Anti oxidants- ascorbic acid, citric acid, EDTA

Question 6

Colligative properties

Answer 6

Properties dependant on the no of solute to solvent particles in solution, not the identity of the solute

Question 7

Vapour pressure depression

Answer 7

Adding non volatile solute to solvent reduces vapour pressure above solution

Question 8

Boiling point elevation (BPE)

Answer 8

Adding non volatile solute to solvent increases boiling point

Change in Tb=Kb x m

Kb= (BPE)

m=mixture of solutes

Question 9

Freezing point depression

Answer 9

Adding non volatile solute to solvent decreases freezing point

Change in Tf=Kf x m

Question 10

Osmotic pressure (pi)

Answer 10

pi= nRT/V=cRT

R=8.31 JKmol

Question 11

Osmotic pressure- van’t hoff factor

Answer 11

with electrolytes pi depends on the number of particles (ie ion)

van’t hoff factor=i

pi=icRT

i applies to other calculations eg. Tf=iKf x m

Question 12

Van’t hoff factor

Answer 12

i=a+b as no of particles= no of ions
some salts do not completely dissociate therefore
i<a></a>

Question 13

Osmolality/Osmolarity

Answer 13

1 mole= amount of solute making up avorgardos number of particles

Osmolality=no of osmoles/kg of solvent
Osmolarity=no of osmoles/litre of solution

Question 14

Osmolality of biological fluids

Answer 14

275-295 mOsm/kg

Often in range 286 mOsm +/- 4

Question 15

Isotonicity

Answer 15

Where there is no net movement of solvent with respect to a biological membrane

Isosmotic is over a perfect semipermeable membrane which biological membranes are not

Question 16

Isotonic/hypertonic/hypotonic

Answer 16

Isotonic: Preferred. required for intraspinal/thecal and mucous membrane admin

Hypotonic: Adjusted with dextrose or NaCl

Hypertonic: Must be administered to large vein or very slowly. May increase absorption of IM drugs