psychomotor stimulants Flashcards
psychomotor stimulants
Amphetamines, Cocaine, Methylxanthines & Convulsive Stimulants
amphetamine (BENZEDRINE, BIPHETAMINE, ADDERAL)
stimulant
d-amphetamine (DEXEDRINE, BIPHETAMINE, ADDERAL)
-greater effect in CNS than amphetamine
Lisdexamfetamine (Vyvanse)
prodrug, amphetamine is linked to lysine
- Moderate rate of conversion to amphetamine limits abuse
- Used for ADHD but might not work as well as traditional amphetamines in some patients
methamphetamine (DESOXYN) - “speed” “crank” - “ice”
- methyl group: resistant to metabolism by MAO and increases its lipid solubility
- intense effects in the CNS, widely abused
- “ice”: crystalline smokable form, like crack
- meth is much longer acting than crack cocaine: 12 hours or more vs 15-30 min. for crack!
methylphenidate (RITALIN)
and (permoline (Cylert) FYI)
similar to amphetamines - used to tx ADD in kids - paradoxical effect of amphetamine and related agents is to stimulate areas of the brain such as the locus ceruleus that enable the child to focus attention
Cathinone (Khat, “Kat”, or “Cat”)
- plant from Eastern Africa and Mid East
- analogs easy to synthesize chemically (DOAs in US, Europe)
- “bath salts” from the internet and in “head shops”.
- usually taken by “snorting”
- Some products include: “Ivory Wave”, “Vanilla Sky”, “Raving Dragon” and “Purple Wave”.
- recently banned by the DEA
Ephedrine
- sympathomimetic agent
- used in various OTC pep pills
- banned by FDA but can get over internet
Modafanil (Provigil) and Armodafanil (Nuvigil)
newer drugs, used to tx narcolepsy and shift work disorders
-unclear MOA, have many amphetamine-like effects
Pharmacological Effects (amphetamine, methamphetamine): CNS
- stimulation: ^arousal and wakefulness via stimulating the reticular activating system
- euphoria: most pleasant, some dysphoric and anxious
- delay of “fatigue induced” decline in intellectual/motor performance
- rebound effects (crash) may lead to cycle of drug use
- tolerance and dependence: both psychological and physical (w/drawal: fatigue, lethargy, depression)
- amphet. psychosis: like paranoid shizo, but reversible
- appetite suppression: action on hypothalamus, tolerance develops
Pharmacological Effects (amphetamine, methamphetamine): Peripheral effects
primarily sympathomimetic
- autonomic - HTN, tachy, arrhythmias, mydriasis (dilated)
- metabolic - decreased food intake; malnutrition
Pharmacological Effects (amphetamine, methamphetamine): toxicity
sympathomimetic effects -
- CV: HTN, tachy, arrhythmias, and sudden death
- CNS: excessive stimulation, hostility, aggression, psychotic reactions (amphetamine psychosis), tactile hallucinations (formication)
- dental problems (meth mouth) and lung damage from smokable forms
MOA
- acute effect: enhanced release and inhibition of the uptake of NE and DA (acute effect)
- possible direct stimulation of alpha receptors in reward centers of brain
- chronic effect: decreased levels of DA in reward centers of brain
pharmacokinetics
- absorption from GI tract
- IV use by abusers
- metabolism by liver but large amounts are excreted unchanged
- enhanced excretion in acidic urine
use of amphetamines
- ADD: “hyperkinetic syndrome” in children - paradoxical effect in that it may stimulate catecholamine pathways in the brain that enable the child to focus attention properly
- narcolepsy
- obesity and weight reduction (but tolerance develops and drugs aren’t effective long term)
- stimulants
- abuse
Cocaine
from Erythroxylon coca plant of Peru and Columbia
hydrochloride vs. free base vs. “crack”:
cocaine “base/paste” (crude coca extract)–>COCAINE-HCL (50-75mg/line)–>cocaine-free base
either heat to remove water–>CRACK (15-25 mg/dose)
or ether extraction/evaporation–>FREE BASE (15-25 mg/dose)
cocaine entry pharmacokinetics
- HCl salt - water soluble; absorption through mucous membranes - commonly “snorted”
- HCl salt - IV use by abusers
- inhalation of the lipid soluble free base forms provides very rapid delivery of a concentrated bolus to the brain
cocaine metabolism
metabolism by plasma esterase and by liver
- half-life of HCl form is about 1 hour
- major metabolite is benzoylecognine