Catecholamines and noncatecholamines are two types of adrenergic drugs that act on the sympathetic nervous system. The main differences between them are:
- Structure: Catecholamines have hydroxyl groups at position 3 and 4 on the benzene ring, while noncatecholamines lack one or both of these hydroxyl groups.
- Actions: Catecholamines mainly have direct actions, while noncatecholamines can have direct, indirect, or dual actions.
- Metabolism: Catecholamines are rapidly metabolized by monoamine oxidase (MAO) or catechol-O-methyltransferase (COMT) enzymes, resulting in shorter half-lives. Noncatecholamines, on the other hand, have longer half-lives because they are not rapidly metabolized by these enzymes.
- Oral administration: Due to their rapid degradation by MAO and COMT, catecholamines cannot be given orally, while most noncatecholamines can be administered orally.
- Blood-brain barrier: Noncatecholamines can cross the blood-brain barrier more easily than catecholamines, which are more polar and have minimal effects on the central nervous system.
- Examples: Examples of catecholamines include adrenaline, noradrenaline, dopamine, and isoprenaline, while examples of noncatecholamines include ephedrine, amphetamine, methylamphetamine, methylphenidate, and phenylephrine.
Comparative Table: Catecholamines vs Noncatecholamines
Here is a table comparing the differences between catecholamines and noncatecholamines:
Feature | Catecholamines | Noncatecholamines |
---|---|---|
Chemical Structure | Contain hydroxyl groups at position 3 and 4 on the benzene ring | Lack one or both hydroxyl groups on benzene ring |
Action | Mainly direct-acting drugs | Mainly indirect-acting or dual-acting drugs; some can be direct-acting |
Receptor Affinity | High affinity for α and/or β receptors | Moderate to poor affinity for adrenoceptors |
Metabolism | Metabolized mainly by MAO or COMT | Poor substrates for MAO and resistant to COMT |
Half-life | Usually shorter due to rapid metabolism | Moderate to longer half-life as these are degraded slowly |
Effectiveness | Usually not effective by oral route and are given parenterally | Most of the drugs are effective orally |
CNS Penetration | Poorly penetrate the CNS and have minimal effect on CNS | Easily pass blood-brain barrier and produce significant CNS effects |
Activity after Adrenergic Denervation | Effects are produced even after adrenergic denervation | Loose activity following adrenergic denervation |
Tolerance | No development of tolerance | Tolerance develops following repeated administration |
Examples of catecholamines include adrenaline, noradrenaline, dopamine, and isoprenaline, while examples of noncatecholamines include amphetamine, ephedrine, pseudoephedrine, and methylphenidate.
Read more
- Catecholamines vs Noncatecholamines
- Catecholamines vs Acetylcholine
- Catecholamines vs Cortisol
- Epinephrine vs Norepinephrine
- Acetylcholine vs Adrenaline
- Atropine vs Epinephrine
- Adrenergic vs Cholinergic Receptors
- Neurotransmitters vs Hormones
- Neuropeptides vs Neurotransmitters
- Cortisol vs Epinephrine
- Phenylephrine vs Phenylpropanolamine
- Excitatory vs Inhibitory Neurotransmitters
- Adrenaline vs Noradrenaline
- Sympathomimetic vs Sympatholytic Drugs
- L Dopa vs Dopamine
- Cholinergic vs Anticholinergic
- Neurons vs Neurotransmitters
- Dopamine vs Serotonin
- Chronotropic vs Dromotropic
- Benzodiazepines vs Nonbenzodiazepines