Lesson B7 - Pharmacology Flashcards
The amphetamines are a class of central nervous system (CNS) stimulant drugs that enhance the activity of
the brain
The amphetamines are synthetic organic compounds that are structurally similar to
norepinephrine, epinephrine and
dopamine found in the body
Three common amphetamine
compounds are
amphetamine, dextroamphetamine, and methamphetamine.
The amphetamines stimulate both the CNS and the
sympathetic nervous system
In the CNS, the amphetamines
act primarily by releasing the neurotransmitters, norepinephrine and dopamine, from
nerve terminals.
The effects produced by amphetamines depend on the drug dose and the
route of administration.
CVS (Cardiovascular System) effects of amphetamine are due to drug-induced displacement
of
norepinephrine from adrenergic nerve terminals, which then acts on postsynaptic α
(vasculature) and β1 (heart) receptors. The effects include:
- Fight-flight response.
- Increased blood pressure.
- Increased heart rate.
CNS effects of amphetamine are mediated by the actions of catecholamines in the CNS,
whereby amphetamine primarily increases release (by displacement) and also
inhibits active reuptake of dopamine and norepinephrine in several brain regions
The CNS stimulation is dose-dependent, with
low doses primarily affecting the cerebral cortex and high doses affecting the entire
cerebrospinal axis, and can manifest as:
- Behavioural and psychomotor stimulation (alertness, hyperactivity, insomnia).
- Anorexia (reduction in appetite).
- Hyperthermia (increase in body temperature).
- Respiratory centre stimulation.
- Neurotransmission in spinal cord.
- Convulsions, with high doses.
The amphetamines act on the following brain areas:
- Reticular activating system (RAS).
- The medial forebrain bundle (MFB) is stimulated.
- Hypothalamus.
- Limbic system.
Therapeutic uses of amphetamine-like drugs:
- Narcolepsy.
- Attention-deficit hyperactivity disorder (hyperactive child syndrome)
- Parkinson’s disease.
Tolerance develops
rapidly to the
euphoria and mood elevating effects (widely abused)
Cessation of administration of the amphetamines results in mood depression that may be
profound, prolonged sleep, huge appetite, lassitude and
fatigue.
Amphetamines usually are self-administered to produce pleasurable effects, including euphoria
and an
abrupt awakening sensation (“rush”)
The abuse liability of the amphetamines is considered to be
extremely high
Inherent harmfulness of the amphetamine reside in
the long-term toxicities