Pharmacology
Drug Metabolism – ADME basics
1. Learning outcomes
Discuss the pros and cons of different routes of administration for drugs
Explain how drugs cross the biological membrane by different routes and how this influences
drug formulation
Describe why basic/acidic groups are useful for improving drug absorption
Apply the theory of lipid solubility to explain effects on drug absorption/efficacy
Be able to apply the theory of VD and the four factors that affect drug distribution to identify the
best therapy.
Implement knowledge of drug design modification to improve penetration of target tissue
2. What do we need to know?
3. ADME - who cares?
Drug companies (developers):
- Too many drugs fail at clinical trials
- Need to develop better second-generation drugs
- Need to develop “niche-population” drugs
Doctors (prescribers):
- Judge the risk-benefit for a drug
- Communication to patients
- Due to interest
4. Fate of drugs in the body
, Pharmacology
Drug Metabolism – ADME basics
5. Routes of absorption
Dependent on drug target area:
- Oral (many drugs)
- Skin (e.g. topical analgesics,
antibiotics)
- Injection (e.g. Insulin)
- Inhalation (e.g salbutamol)
Drug must cross cell membrane
to reach target
- Passive diffusion
- Facilitated Diffusion
- Active transport
- Pinocytosis
6. Solubility and dissolution
Solubility is the concentration of a saturated solution of drug at a specified temperature and
pressure.
A drug must be in solution (molecular form) for absorption to take place
Dissolution is the rate at which a drug goes into solution
7. Oral
administration
Easy for patient = high compliance
Ionisation affects:
- rate at which drugs permeate membranes, if ionised it can get through the barrier
- ratio of ionised to unionised drug is governed by the pKa of the drug and the pH of that
compartment
Drug must move from GI Tract into plasma
8. pH and ease of distribution
steady-state distribution of drug molecules between aqueous compartments when a pH
difference exists between them.
Drug Metabolism – ADME basics
1. Learning outcomes
Discuss the pros and cons of different routes of administration for drugs
Explain how drugs cross the biological membrane by different routes and how this influences
drug formulation
Describe why basic/acidic groups are useful for improving drug absorption
Apply the theory of lipid solubility to explain effects on drug absorption/efficacy
Be able to apply the theory of VD and the four factors that affect drug distribution to identify the
best therapy.
Implement knowledge of drug design modification to improve penetration of target tissue
2. What do we need to know?
3. ADME - who cares?
Drug companies (developers):
- Too many drugs fail at clinical trials
- Need to develop better second-generation drugs
- Need to develop “niche-population” drugs
Doctors (prescribers):
- Judge the risk-benefit for a drug
- Communication to patients
- Due to interest
4. Fate of drugs in the body
, Pharmacology
Drug Metabolism – ADME basics
5. Routes of absorption
Dependent on drug target area:
- Oral (many drugs)
- Skin (e.g. topical analgesics,
antibiotics)
- Injection (e.g. Insulin)
- Inhalation (e.g salbutamol)
Drug must cross cell membrane
to reach target
- Passive diffusion
- Facilitated Diffusion
- Active transport
- Pinocytosis
6. Solubility and dissolution
Solubility is the concentration of a saturated solution of drug at a specified temperature and
pressure.
A drug must be in solution (molecular form) for absorption to take place
Dissolution is the rate at which a drug goes into solution
7. Oral
administration
Easy for patient = high compliance
Ionisation affects:
- rate at which drugs permeate membranes, if ionised it can get through the barrier
- ratio of ionised to unionised drug is governed by the pKa of the drug and the pH of that
compartment
Drug must move from GI Tract into plasma
8. pH and ease of distribution
steady-state distribution of drug molecules between aqueous compartments when a pH
difference exists between them.
