L68: Drug Administration And Dosage Form

Question 1

Parenteral route

Answer 1

Dosage form:

• solution
• suspension (only SC and IM)
• emulsion
• powder for reconstitution

1. IV (superficial vein / subclavian vein)
   - injection vs infusion (physical characteristics, fluid pressure, height of infusion)
   - Advantage: quick response, 100% bioavailability, oral route cannot use (unconscious)
   - Disadvantage: trained personnel, w/o emulsion or suspension cannot be used
2. SC (slower absorption)
   - Advantage: can be given by patient, 100% bioavailability
   - Disadvantage: small volume only (1 ml), painful, lipohypertrophy / lipoatrophy
3. IM
   - gluteal: adult, larger volume
   - deltoid: rapid absorption
   - vastus lateralis: infant/children
   - Advantage: large volume (2 ml), faster then SC
   - Disadvantage: trained personnel, site of injection influence absorption
4. Intradermal
   - 0.1 ml between epidermis and dermis
   - slow absorption
   - diagnostic test
5. Intra-arterial
   - rapid dispersal of drug
   - target a specific organ
   - manipulative difficulties
6. Intracardiac
   - aqueous solution
   - emergency for local effect
7. Intraspinal
   - aqueous solution
   - less than 20 ml
   - subarachnoid / epidural
8. Intraarticular
   - aqueous solution / suspension
   - synovial fluid
   - local administration of anti-inflammatory
9. Implant
   - solid dosage under the skin
   - contraceptive / HRT
   - slow, long term
   - sterile

Question 2

Oral route

Answer 2

1. Local effect e.g. antacids
2. Systemic effect e.g.solution, suspension, emulsion, tablets, capsules, granules/powders

Advantage: simple, convenient, self-administration, safe, cheap to produce
Disadvantage: 1st pass metabolism, slow onset, irregular absorption, solubility issues, GI motility, unconscious / vomiting / pre/post-operative use

Dosage form:
Liquid form: easier to swallow for dysphagia
Solid form: convenient to carry, stable, accuracy of dosage, mask unpleasant taste, enteric coated/ sustained-release form available
- Enteric coated: for drugs degraded by gastric juice / irritate gastric mucosa, avoid indigestion remedies
- Sustained release: swallowed whole do not chew

Question 3

Buccal route

Answer 3

1. Local effect e.g. lozenge for sore throat
2. Systemic e.g. GTN for angina

• Saliva: dissolution of drug
• Vascular nature: facilitate drug absorption

Advantage: rapid absorption, no 1st pass, stable in neutral pH saliva, unconscious/vomiting patient
Disadvantage: inconvenient to hold in mouth, only small doses

Question 4

Topical route

Answer 4

1. Local effect e.g. lotion, cream, ointment
2. Systemic effect e.g. transdermal patch

Advantage: avoid 1st pass, bypass gastric juice
Disadvantage: potent drugs needed for systemic effect

Question 5

Rectal route

Answer 5

1. Local e.g. constipation
2. Systemic e.g. diazepam for epilepsy

Dosage form:
- suppository, enema

Advantage: cannot use oral route, reduce 1st pass
Disadvantage: irregular absorption, less convenient

Question 6

Vaginal route

Answer 6

Local effect ONLY

Dosage form:

• pessary
• tablets/capsules
• cream

Question 7

Inhalation route

Answer 7

1. Local effects e.g. bronchodilators, nasal congestion
2. Systemic effects e.g. anaesthesia

Dosage form:

• Inhalation
• aerosol
• powder

Advantage:
- Local: reduce side effects due to smaller dose
- Systemic: quick absorption due to high blood flow to lungs
Disadvantage: special technique, cannot use > 20 microns

Question 8

Nasal route

Answer 8

1. Local effects: decongestant
2. Systemic effects: desmopressin for diabetes insipidus

Dosage form:

• spray
• drop

Advantage:

• good vascularity for drug absorption
• avoid 1st pass

Question 9

Eye route

Answer 9

Local effects ONLY

Dosage form:

• drop
• ointment
• discard after 4 weeks of opening
• drops 10 minutes before ointment

Question 10

Ear drops

Answer 10

Local effect ONLY

• warm the ear-drop bottle by holding in hand for a few minutes
• adult: hold earlobe upward and backward
• children: hold earlobe downward and backward