Modafinil
Noting the below were the chloro analogues dismissed due to higher toxicity/side effect issues or ????
From WikiP
Pharmacology
The exact mechanism of action is unclear, although in vitro studies have shown it to inhibit the reuptake of dopamine and, more potently, norepinephrine. While the co-administration of a dopamine antagonist is known to decrease the stimulant effect of amphetamine, it does not negate the wakefulness-promoting actions of modafinil. Modafinil activates glutamatergic circuits while inhibiting GABAergic neurotransmission. Modafinil is thought to have less potential for abuse than other stimulants due to the absence of any significant euphoric or pleasurable effects.
The central stimulating effect of modafinil shows dose and time-related features. The effect tends to be enhanced by chlorination but reduced by methylation. Modafinil blocks the reuptake of norepinephrine by the noradrenergic terminals on sleep-promoting neurons from the ventrolateral preoptic nucleus (VLPO). Such a mechanism could be at least partially responsible for the wake-promoting effect of modafinil.
Modafinil has a binding coefficient (Ki) of about 4,000 nmol/L for the dopamine reuptake transporter, and in excess of 10,000 nmol/L for the norepinephrine reuptake transporter.
A newly proposed mechanism of action involves brain peptides called orexins, also known as hypocretins. Orexin neurons are found in the hypothalamus but project to many different parts of the brain, including several areas that regulate wakefulness. Activation of these neurons increases dopamine and norepinephrine in these areas, and excite histaminergic tuberomammillary neurons increasing histamine levels there. There are two receptors for hypocretins, namely hcrt1 and hcrt2. Animal studies have shown that animals with defective orexin systems show signs and symptoms similar to narcolepsy. Modafinil seems to activate these orexin neurons thus promoting wakefulness. However, a study of genetically modified dogs lacking orexin receptors showed that modafinil still promoted wakefulness in these animals, suggesting that orexin activation is not required for the effects of modafinil.
It is possible that modafinil acts by a synergistic combination of mechanisms including direct inhibition of dopamine and norepinephrine reuptake, as well as orexin activation.
It has been shown in rats that modafinil increases histamine release in the brain, and this may be a possible mechanism of action in humans.[32]
Modafinil used in a randomized double blind study showed that normal healthy volunteers between the ages of 30-44 showed general improvement in alertness as well as mood. In the 3 day study, counterbalanced, randomized, crossover, inpatient trial of modafinil 400 mg was administered as well as a placebo to the control group. The conclusion demonstrated that modafinil may have general mood elevating effects in particular for the adjunctive use in treatment-resistant depression.[21]
[edit] Pharmacokinetics
Modafinil induces the cytochrome P450 enzymes CYP1A2, CYP2B6 and CYP3A4, as well as inhibiting CYP2C9 and CYP2C19 in vitro. It may also induce P-glycoprotein, which may affect drugs transported by Pgp, such as digoxin.
Cmax occurs approximately 2–3 hours after administration. Food will slow absorption, but does not affect the total AUC. Half-life is generally in the 10–12 hour range, subject to differences in CYP genotypes, liver function and renal function. It is metabolized in the liver, and its inactive metabolite is excreted in the urine
.
