15 Appendices
used at Erowid with the permission of author William White15.1 Appendix 1: P450 Inhibiting Drugs
This is a partial list of recreational and medical drugs which inhibit the P450 enzymes 2D6, 3A4, and 3A5. Not all of them will inhibit all of the P450 enzymes, but it's safe to say that a substantial number of these will interact with DXM.
Generally speaking, inhibitors of P450-2D6 include antidepressants (both SSRIs and tricyclics, and possibly MAO inhibitors), antiparasitics (especially antimalarials), antihistamines (both prescription and over-the-counter), neuroleptics, beta blockers (drugs for high blood pressure), and antineoplastics (anti-cancer drugs). Methadone is a P450-2D6 inhibitor, and it is likely that many alkaloids, especially of plant origin, may be mild to moderate P450-2D6 inhibitors.
Drug | Uses | P450-2D Enzymes | Potency | Ref |
---|---|---|---|---|
ajmalicine | 2D6 | strongest | (164) | |
carbon monoxide | poison | 2D6 | (160) | |
chloroquine | antiparasitic | 2D6 | med-low | (172) |
chlorpheniramine | antihistamine | 2D | med-high | (151) |
citalopram | antidepressant | 2D6 | med-low | (166) |
clozapine | antipsychotic | 2D6 | low | (171) |
desipramine | antidepressant | 2D6 | low | (152) |
diphenhydramine | antihistamine | 2D | med-high | (151) |
doxorubicin | anticancer | 2D6 | med-low | (165) |
fluoxetine | antidepressant | 2D6 | med-high | (152) |
fluvoxamine | antidepressant | 2D6 | med-high | (152) |
imipramine | antidepressant | 2D6 | med | (152) |
lomustine | anticancer | 2D6 | med | (165) |
mepyramine | antihistamine | 2D6 | high | (151) |
methadone | addiction treatment | 2D6 | med | (162) |
moclobemide | MAO-A Inh. (reversible) | 2D6, also 2C19, 1A2 | (147) | |
nortryptiline | antidepressant | 2D6 | med-low | (155) |
oxamniquine | antiparasitic | 2D6 | med-low | (172) |
paroxetine | antidepressant | 2D6 | high | (152) |
PCP | recreational | 2D | (150) | |
primaquine | antiparasitic | 2D6 | med-low | (172) |
propranolol | beta-blocker | 2D6 | low | (156) |
quinidine | 2D6 | (148) | ||
quinine | antiparasitic | 2D | (151) | |
sertraline | antidepressant | 2D6 | med-high | (167) |
triprolidine | antihistamine | 2D | med-high | (151) |
vinblastine | anticancer | 2D6 | med-low | (165) |
vinorelbine | anticancer | 2D6 | med-low | (165) |
Drug | Uses | P450-3A Enzymes | Potency | Ref |
7,8-benzoflavone | 3A4 (activator) | (153) | ||
cannabidiol | component of marijuana | 3A | med | (161) |
cocaine | recreational | 3A | low | (157) |
clotrimazole | agricultural fungicide | 3A (activator) | very high | (154) |
cyclophosphamide | 3A | low? | (158) | |
ifosfamide | 3A | low? | (158) | |
ketoconazole | 3A | (145) | ||
pilocarpine | cholinomimetic | 3A | low | (149) |
Drug | Uses | P450-3A Enzymes | Potency | Ref |
1-aminobenzotriazole | Nonspecific | med-high | (159) | |
chlorophyllin | geriatric | Nonspecific | (146) | |
general anaesthetics | Nonspecific | (163) |
One reference ((164)) gives the general characteristics of P450-2D6 inhibitors as
A computer model of the P450-2D6 cytochrome has been constructed ((170)).
15.2 Appendix 2: Neuropharmacology of Recreational Drugs
- 2CB
- Like many phenethylamines, has mixed properties of a dopamine releasing agent, serotonin (5HT) releasing agent, and probably binding specifically to 5HT receptors (likely including 5HT2A and 5HT2C). Compare amphetamine, MDA.
- alcohol
- Mechanism unknown; may affect membrane permeability or alter ion channel function. Functionally potentiates GABAergic activity and blocks NMDA receptors, and also has actions on other ion channel receptors.
- amyl nitrite
- Vasodilator; recreational effects probably derive from this effect rather than being specific to a set of receptors.
- amphetamine
- Causes a non-vesicular release of dopamine and noradrenaline by neurons which normally secrete them. May have some direct effect on dopamine and noradrenaline receptors, but this is insignificant compared to its neurotransmitter releasing effect.
- barbiturates
- Targets and binds to a specific site (called the picrotoxin site) on GABA receptors, which activates them. This is a different site from alcohol and benzodiazepines, so that if you combine any of these three, they will not compete for the same binding sites. Consequently, there is a synergistic effect, which can be quite dangerous.
- benzodiazepines
- Similar to barbiturates, except for two factors. First, the binding site is the benzodiazepine site on the GABA receptor. Second, when a benzodiazepine binds to this site, the GABA receptor is not immediately activated; instead, the natural action of GABA is enhanced. This is the main reason benzodiazepines are safer than barbiturates, and have different effects.
- "blues"
- An antihistamine (targeting and activating the H1 receptor) which probably has sigma1 antagonist properties; when used in combination with pentazocine, it probably blocks the sigma activity of the latter. Rarely found. The only reason I'm mentioning it is because I heard about it in a comedy skit called "Rock and Roll Doctor" and always wondered what "blues" were (until I found out). Well, if you wondered too, now you know.
- caffeine
- Targets and blocks an adenosine receptor, probably A2 but possibly A1. This is an inhibitory presynaptic receptor, i.e., when activated it decreases the amount of neurotransmitter released by a neuron. Thus, caffeine blocks some of this inhibition, increasing neural activity.
- cannabis
- Targets a specific receptor (or family of receptors) designated anandamide. It is not yet known whether cannabis (actually, THC) is an agonist or antagonist at this receptor, although most think it is an agonist.
- codeine
- See morphine.
- coffee
- See caffeine.
- cocaine
- A dopamine reuptake inhibitor; cocaine blocks the transporter which takes used dopamine out of the way. Thus, dopamine secreted by a neuron keeps activating receptors over and over. Cocaine is also a sigma1 agonist, and has blocking abilities on certain ion channels (by which it exerts its local anesthetic effects).
- Demerol
- See morphine.
- glue
- See solvents.
- heroin
- See morphine.
- ketamine
- Blocks NMDA receptors at the same site as DXM and PCP.
- LSD
- Targets 5HT2A and 5HT2C, where it acts either as an antagonist or a partial agonist. Also has some dopaminergic activity; however, the majority of its effects are mediated through the 5HT receptors.
- marijuana
- See cannabis.
- MDA
- See MDMA. Release binding spectrum is probably different, and MDA may have additional effects on receptors.
- MDMA
- Similar to amphetamine, except that MDMA causes a nonvesicular release of dopamine and serotonin (5HT). Probably has other effects as well, some of which may be significant.
- methamphetamine
- Similar to amphetamine, possibly with more dopamine release.
- morphine
- Targets opioid receptors mu, kappa, and delta, where it acts as an agonist. Slight differences in binding spectrum to opiate receptors exist among the various natural and synthetic opiates.
- nicotine
- Stimulates and then blocks nicotinic acetylcholine receptors.
- nitrous oxide
- Seems to affect phospholipid membranes, although some effects may be mediated by NMDA and GABA channels, and other ion channels. General anesthetics are similar to nitrous oxide, although more toxic.
- opium
- See morphine.
- PCP (phencyclidine)
- PCP and related cycloarylpiperidines block NMDA receptors, as well as having a variety of other effects, including sigma agonism, dopamine reuptake inhibition, and specific effects on an unknown cerebellar receptor.
- Poppers
- See amyl nitrite
- Psilocybin (mushrooms)
- Similar to LSD; acts via 5HT2A and 2C receptors and possibly additional ones.
- Quaaludes (methaqualone)
- See barbiturates.
- Ritalin
- Similar to amphetamine, prescribed for Attention Deficit Disorder
- Rohypnol
- See benzodiazepines.
- seconal
- See barbiturates.
- solvents
- Same general theory as alcohol and nitrous oxide, but considerably more toxic to neurons (and the liver).
- Valium[tm]
- See benzodiazepines.
- yohimbine
- Targets and blocks alpha2 adrenergic receptors. These are autoreceptors, which normally limit the activity of adrenergic neurons. By blocking alpha2 receptors, yohimbine increases the activity of these neurons.
15.3 Appendix 3: Other Sigma and NMDA Ligands
Here are a few sigma ligands you may wish to research (if you are interested in that sort of thing):
Sigma1 ligands in rough order of potency:
- (+)-pentazocine
- haloperidol
- DTG
- (+)-3-PPP
- DXM
- (+)-SKF 10,047
- (+)-cyclazocine
- (-)-pentazocine
- PCP
- (-)-SKF 10,047
Sigma2 ligands in rough order of potency:
- DTG
- haloperidol
- (+)-3-PPP
- (-)-pentazocine
- PCP
- (+)-pentazocine
- (-)-SKF 10,047
P> A known sigma antagonist is N-[-2-(3,4-dichlorophenyl)ethyl]- N-methyl-2-[1- pyrimidinyl-1-piperazine] butanol; a sigma1 selective antagonist is (1-(cyclopropylmethyl)- 4-2'4"-fluorophenyl)- (2'-oxoethyl)piperidine HBr.