Experimental Animals

As. noted. in. Section. 2.2.2,. symptoms. of. acute. amphetamine. toxicity. in. rats. and. mice. include.

hyperactivity,. piloerection,. salivation,. hyperpnea,. dilated. pupils,. and. convulsions.. Symptoms. of.

acute.methamphetamine.toxicity.in.rodents.were.reported.as.excitement,.convulsions,.and.changes.in.

Appendix II

for.d,l-amphetamine.and.methamphetamine.in.various.species.are.summarized.in.Table.21.and.Table.

22.(Section.2.2.2)..

Neuroanatomical. evidence. of. toxicity. has. also. been. reported. following. amphetamine. or.

methamphetamine. exposure.. Findings. have. included. swollen. nerve. fibers. and. terminals. in. rats.

and. mice. (reviewed. in.(27)),. reduction. of. brain. dopaminergic. axons. and. axon. terminals. in. rats.

and.monkeys,.and.reduction.of.serotonergic.axons.and.axon.terminals.in.rats.(reviewed.in.(72))..

Continuous.iv.infusion.of.rats.with.amphetamines.at.1.mg/kg.bw/hour.for.12.days.resulted.in.reduced.

brain.norepinephrine.and.cardiac.catecholamine.levels.and.increased.motor.activity.and.stereotypic.

behaviors. (reviewed. in.(24)).. Repeated. parenteral. dosing. of. rodents. with. methamphetamine. has.

caused.excitement,.weight.loss.or.decreased.weight.gain,.alteration.in.classical.conditioning,.changes.

in.pancreas,.and.hemorrhage.(70)..

Effects.of.repeated.dietary.exposure.of.rats.and.mice.to.d,l-amphetamine.were.reported.in.an.NTP.

study.(24)..Hyperactivity,.reduced.feed.intake,.and.decreased.body.weight.were.commonly.observed.

in.rats.and.mice..Following.13.weeks.of.exposure,.final.body.weights.were.more.than.10%.lower.

compared.to.controls.at.dietary.amphetamine.concentrations.of.≥188.ppm.in.rats.and.at.125.(females).

and.250.(males).ppm.in.mice..

2.6.3 Genetic toxicity

With. the. exception. of. an. equivocal. mutagenicity. response. in.S. typhimurium. strain. TA98,. d,l-amphetamine.produced.negative.results.in.mutagenicity.testing.of.additional.S. typhimurium.strains.

and.E. coli.and.in.sister.chromatid.exchange.and.chromosomal.aberration.assays.in.Chinese.hamster.

ovary.cells.(24, 34)..In.in vivo.micronucleus.assays.in.mice,.micronucleus.frequency.was.not.increased.

in.1.study.with.dosing.up.to.10.mg/kg.bw.(34),.but.was.increased.in.a.second.study.at.doses.≥12.5.

mg/kg.bw.(73)..

2.6.4 Carcinogenicity

In.a.2-year.GLP.dietary.carcinogenicity.study,.there.was.no.evidence.of.neoplasia.at.d,l-amphetamine.

doses.up.to.100.ppm.(~5.mg/kg.bw/day.in.rats.and.19.–.30.mg/kg.bw/day.in.mice).(24, 71)..An.increase.

in.lesions.such.as.cataracts,.retinal.atrophy,.and.bone.myelofibrosis.in.rats.and.ovarian.atrophy.in.mice.

did.not.appear.to.have.been.directly.caused.by.drug.exposure..The.study.authors.concluded.that.there.

was.no.evidence.of.carcinogenic.activity.of.d,l-amphetamine.sulfate.in.male.or.female.F344/N.rats.

or.B6C3F₁.mice.

2.6.5 Potentially susceptible populations

Polymorphisms.for.CYP2D6,.the.enzyme.involved.in.the.aromatic.hydroxylation.of.amphetamines.in.

humans.and.rats,.are.associated.with.at.least.12.variants.that.alter.enzyme.activity.(reviewed.by.(74, 75)..Poor.metabolizer.phenotypes.occur.in.5.–.8%.of.whites.and.2.–.10%.of.blacks.and.Asians..CYP2C3.

is.involved.in.amphetamine.deamination.reactions.in.rabbits.(25)..The.enzyme.is.not.a.member.of.the.

CYP2C.human.gene.family.(76),.but.the.Expert.Panel.finds.it.reasonable.to.assume.that.one.or.more.

members.of.the.CYP2C.family.may.be.involved.in.deamination.reactions.in.humans..The.gene.family.

is.highly.polymorphic.with.functional.variants.identified.at.CYP2C9.and.CYP2C19.loci..Two.of.three.

known.defective.alleles.of.CYP2C9.result.in.decreased.activity..CYP2C19.polymorphisms.resulting.

in.slow.metabolizer.phenotypes.are.present.in.3%.of.Caucasians.and.nearly.20%.of.Asians.(77).

Appendix II

Two.studies.examined.the.effects.of.methamphetamine.on.Dark.Agouti.rats,.which.have.a.CYP2D1.

polymorphism. that. results. in. poor. methamphetamine. metabolism. in. females. and. intermediate.

metabolism.in.males.(48, 78)..Administration.of.methamphetamine.30.mg/kg.bw.sc.twice.daily.on.

PND.11.–.20.did.not.affect.behavioral.testing.results.in.offspring.of.Dark.Agouti.versus.Sprague-Dawley.rats,.but.mortality.was.higher.in.male.and.female.Dark.Agouti.rat.offspring.compared.to.

Sprague-Dawley.rats..In.a.second.study,.sc.injection.with.15.mg/kg.bw.methamphetamine.on.PND.

11.–.20.resulted.in.less.effective.performance.on.the.Morris.Maze.test.of.spatial.learning.and.memory.

in.female.Dark.Agouti.rats.and.greater.acoustic.startle.amplitudes.in.male.and.female.Dark.Agouti.

rats.compared.to.Sprague-Dawley.rats..Inhibition.of.methamphetamine.4-hydroxylation.in.rats.was.

reported. to. enhance. stereotyped. behavior. in. rats,. but. reviewers. noted. that. metabolic. differences.

in.humans.versus.animals.complicate.the.application.of.the.study.findings.to.humans.with.inborn.

CYP2D6.deficiencies.(reviewed.in.(30)).

Comparison.of.d,l-amphetamine.pharmacokinetics.parameters.in.adults.versus.children.indicated.

that.half-life.is.shorter.in.children.and.bioavailability.is.lower.in.children.when.adjusted.for.weight.

differences.(34)..A.comparison.of.d-amphetamine.responses.in.hyperactive.boys.and.men.demonstrated.

that.activity.was.decreased.to.a.greater.extent.in.hyperactive.boys,.and.that.while.hyperactive.boys.

reported.feeling.cranky.and.more.tired,.the.men.reported.feeling.euphoric.and.less.tired.(81)..

Eleven.studies.compared.neurological.effects.following.amphetamine.or.methamphetamine.exposure.

in.developing.versus.adult.animals.in.an.attempt.identify.mechanisms.responsible.for.discordant.

responses.in.adults.versus.children..Summaries.of.those.studies.and.their.references.are.included.in.

Section.2.5.3..Amphetamine.studies.in.rats.suggested.age-related.alterations.in.dopamine.release,.

firing.of.dopaminergic.neurons,.and.sensitization.following.challenge.dosing,.while.mouse.studies.

suggested. alterations. in. corticosterone. release. and.ΔFosB. expression.. Methamphetamine. studies.

in.rats.demonstrated.age-related.alterations.in.dopamine.release.or.turnover,.tyrosine.hydroxylase.

activity,.susceptibility.to.glial.cell.proliferation,.toxicity.to.glutamate.positive.neurons,.or.alterations.

in.dorsal.protein.kinase.A.activity.

Appendix II