Amphetamines administration routes

In neurochemical terms, amphetamine and cocaine boost monoamine activity. Amphetamine has a threefold mode of action first, it causes dopamine and noradrenaline to leak into the synaptic cleft second, it boosts the amount of transmitter released during an action potential and third, it inhibits the reuptake of neurotransmitter back into presynaptic vesicles. These three modes all result in more neurotransmitter being available at the synapse, thus generating an increase in postsynaptic stimulation. Cocaine exerts a similar overall effect, but mainly by reuptake inhibition. The main neurotransmitters affected are dopamine and noradrenaline, although serotonin is boosted to a lesser extent. These modes of action are outlined in Chapter 3, and the neurochemical rationale for drug tolerance is covered more fully in Chapter 10. The main differences between amphetamine and cocaine are their administration routes (summarised above) and the more rapid onset and shorter duration of action for cocaine. 

If disturbances of gastrointestinal function prevent the use of oral sustained-release morphine, the fentanyl transdermal system (fentanyl patch) can be used over long periods. Furthermore, buccal transmucosal fentanyl can be used for short episodes of breakthrough pain (see Alternative Routes of Administration). Administration of strong opioids by nasal insufflation has been shown to be efficacious, and nasal preparations are now available in some countries. Approval of such formulations in the USA is growing. In addition, stimulant drugs such as the amphetamines have been shown to enhance the analgesic actions of the opioids and thus may be very useful adjuncts in the patient with chronic pain. 

When indicated for therapeutic use, 5 to 60 mg or 5 to 20 mg of amphetamine or methamphetamine, respectively, are administered orally. An oral dose of amphetamine typically results in a peak plasma concentration of 110 ng/ml.2 When abused, amphetamines may be self-administered by the oral, intravenous, or smoked route. The last route of administration is common for methamphetamine. With heavy use, addicts may ingest up to 2000 mg per day. 

The subjective effects of all the psychostimulants depend on personality, the environment in which it is administered, the dose of the drug, and the route of administration. For example, moderate doses of D-amphetamine (10-20 mg) in a normal person will produce euphoria, a sense of increased energy and alertness, anorexia, insomnia, and an improvement in the conduct of repetitive tasks. Some people become anxious, irritable and talkative. As the dose of amphetamine is increased, the symptoms become more marked and the influence of the environment less pronounced. 

The most common route of khat administration is chewing the fresh leaves of the plant. The juices are swallowed and contain two stimulants cathine and cathinone. These substances produce effects that are very similar to cocaine and amphetamine mediated by actions on the monoamine neurotransmitter systems. Users report that... 

Whole body autoradiography may also be used to expose differences in distribution after different routes of administration. Qoforex (ethyl-A-(2-/>-chlorphenyl-l,l-dimethyl) carbonate) is a drug structurally related to a series of nuclear substituted phenylalkylamines of which amphetamine is the parent compound. It has potent appetite-depressing properties and has been widely used in the treatment of obesity. Compounds used for obesity, how-... 

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