Administration

Question 1

What does drug half-life mean?

Answer 1

The half life or ‘t1/2’ of a drug is the time taken for the blood concentration to fall by a half.

Question 2

What is the therapeutic range?

Answer 2

Maximum safe concentration (MSC) / Minimum effective concentration (MEC) = therapeutic window (T)

Question 3

What is the acccumulated dose at 18 hours?

Answer 3

0 hours = 100mg = 100mg accumulated dose
6h = 100 + 50 = 150mg
12h = 100 + 50 +25 = 175mg

18 hours = 100 + 50 + 25 + 12.5 = 188.

Question 4

Why use oral administration?

Answer 4

convenient
economical
portable
safe (usually)
pain-free
variety of dosage forms
no sterilisation needed

BUT
Concordance required
absorption variable

Question 5

What is bioavailability?

Answer 5

The proportion of the drug in a dosage form which reaches the systemic circulation.

Question 6

What is first-pass metabolism?

Answer 6

The liver (or gut wall) extracts and metabolises some drugs so efficiently that the amount reaching the systemic circulation is considerably less than the amount absorbed.

Question 7

Why use sublingual administration

Answer 7

Because the same drug, given sublingually, bypasses the gut wall and liver, avoiding first-pass effect and thus more drug reaches the circulation.

Question 8

Advantages and disadvantages of sublingual?

Answer 8

ADV-
-bypasses first pass effect
-bypasses destruction by stomach acid
-drug stability maintained because the pH of saliva is relatively neutral
-may cause immediate pharmacological effects.
DISADV
- limited to certain types of drugs that can be taken in small doses
- may lose part of the drug if swallowed.

Question 9

What is the sublingual route?

Answer 9

Sublingual administration involves placing a drug under your tongue to dissolve and absorb into your blood through the tissue there.

Question 10

Why use the rectal route of administration?

Answer 10

• useful in the presence of nausea and vomiting
• may reduce first-pass metabolism to a limited extent
• mainly used for topical effects, e.g. treatment of haemorrhoids.

Question 11

Advantages and disadvantages of rectal route?

Answer 11

ADV
- partially bypasses first-pass effect
- bypasses destruction by stomach acid
- ideal if drug causes vomiting
- ideal in patients who are vomiting or comatose.
DISADV-
- drugs may irritate the rectal mucosa
- not a well-accepted route
- not convenient

Question 12

Advantages of intravenous route?

Answer 12

ADV

• 100% bioavailability (bypasses absorption)
• rapid effects
• useful in emergencies
• allows titration of dosage since able to adjust dose
• suitable for large volumes
• irritating substances an be given if well diluted
• ideal for high molecular weight proteins and peptide drugs

Question 13

Disadvantages of intravenous route?

Answer 13

DISADV

• relatively expensive
• requires trained administrators
• increased risk of ADR
• requires slow infusions
• unsuitable for oily substances
• pain

Question 14

To what degree are
Intradermal (I.D)
Subcutaneous (S.C)
Intramuscular (I.M) 
administered?

Answer 14

I.D - 10 to 15 degree angle
S.C - 45 degree angle
I.M - 90 Degree angle

Question 15

Advantages of subcutaneous injections?

Answer 15

ADV

• can be given by patient, e.g. insulin.
• absorption is usually complete
• absorption can be fast from aqueous solution
• suitable for some poorly soluble suspensions and slow-release implants.

Question 16

Disadvantages of subcutaneous injections?

Answer 16

DISADV

• can be painful
• can be a problem finding suitable sites for repeat injection
• irritant drugs can cause local tissue damage
• maximum of -2ml injection

Question 17

Advantages of IM injections

Answer 17

ADV

• Prompt absorption of aqueous solutions
• slow, sustained absorption from repository preparations
• suitable for moderate volumes
• suitable for oily vehicles and some irritating substances
• preferable to IV if patient must self-administer

Question 18

Disadvantages of IM injections

Answer 18

DISADV

• often the most painful routes
• immediate cost
• trained administrators needed
• can cause IM haemorrhage (problematic in anticoagulated patients)
• can cause elevation of laboratory tests, especially creatine kinase.

Question 19

Advantages of inhaled route

Answer 19

ADV

• ideal for gases
• effective for patients with respiratory problems
• doses can be titrated
• localised effect to target lungs: lower doses used compared to that with oral or parenteral administration
• fewer systemic side-effects

Question 20

Disadvantages of inhaled route

Answer 20

DISADV

• most addictive route
• patient may have difficulty regulating dose
• some patients may have difficulty using inhalers.

Question 21

Advantages of transdermal route

Answer 21

ADV -

• Bypasses first-pass effect
• convenient and painless
• ideal for drugs that are lipophilic and have poor oral bioavailability
• ideal for drugs that are quickly eliminated from the body
• irritating substances can be given if well diluted

Question 22

Disadvantages of transdermal route

Answer 22

DISADV0

• some patients are allergic to patches which can cause irritation
• drug must be highly lipophilic
• may cause delayed delivery of a drug to the pharmacological site of action
• limited to drugs that can be taken in small daily doses.

Question 23

Advantages of topical route

Answer 23

ADV

• suitable when local effect of drug is desired
• may be used for skin, eye, vaginal and intranasal products
• minimises systemic absorption
• easy for patient

Question 24

Disadvantages of topical route

Answer 24

DISADV

• some systemic absorption can occur
• unsuitable for drugs when high molecular weight and poor lipid solubility
• may cause delayed delivery of a drug to the pharmacological site of action
• limited to drugs that can be taken in small daily doses.

Question 25

What is topical administration?

Answer 25

Drug that is applied to skin or mucous membranes for local effect, e.g.
skin, eyes, ears, vagina, nose.