Common Drugs Of Abuse

Opiates and Opioids (Morphine, codeine, heroin, meperidine, hydromorphone, and other opioid agonists) all act on the same receptor site and the mechanism for producing dependence is the same.

Sympathomimetic Stimulants (Cocaine, amphetamines, methylphenidate, and other related stimulants) these give us most concern… all of these drugs are capable of releasing incredible amounts of norepinephrine (NE), and the cardiovascular effects are substantial

Depressants (Barbiturates, nonbarbiturate sedatives, benzodiazepines, and ethanol) may be taken because people are on some drug that amps them up and they want to come down. These are extremely dangerous, with a narrow therapeutic index; the dose that can provide a therapeutic sedative or anti-epileptic effect is very close to that which can kill someone (especially with respect to the barbiturates, its easy to overdose and produce respiratory depression and cardiovascular collapse).

Hallucinogens (LSD, mescaline, MDMA, and others  “designer drugs”) people say that their artistic and creative powers are greater while on hallucinogens…

Others (PCP, marijuana, inhalants, nicotine, and caffeine)

Dopamine (a catecholamine neurotransmitter) has no risk for dependence or abuse. Methamphetamine is speed, amphetamine, and mescaline. Ecstacy (MDMA) has the most lethal potential. LSD has a unique structure. Ecstasy and LSD seems to have more of a serotonin component, whereas the methamphetamine class has more of a NE/ catecholamine mediated effect.

Phencyclidine (PCP) has an enormous dissociative effect, used as dissociative anesthesia but has no therapeutic role in humans.

What happens when individuals take these substances? The usual problem is overdose; they misjudge the potency of the heroin or whatever they’re taking. As a result of overdosing on a depressant, there is respiratory depression, hypotension and cardiovascular collapse – shock. If you overdose on a stimulant you get massive CNS stimulation, hypertension, coronary constriction, and sudden cardiac death.

People nowadays will grind up oxycodone or hydrocodone and inject it, to get parenteral effects from these drugs that are usually taken orally. Oxycodone is coming under intense scrutiny by the DEA, so as a practitioner its probably best to simply avoid oxycodone (usually used in combination with aspirin (Percodan) or acetaminophen (Percocet)).

Pregnant drug abusers have a high risk for problems with their children.

Obviously there are tremendous risks for people who inject themselves full of drugs, such as contracting HIV, bacterial endocarditis, hepatitis… all of these are well-known consequences of parenteral drug use due to dirty needles or shared needles.

Cannabinoids are the active ingredients in marijuana; THC is the major cannabinoid with psychoactivity. Marinol is an officially approved drug, which is really THC (tetrahydrocannabinol). It is legally prescribable, and is a schedule III controlled substance; you don’t need a triplicate prescription form. Marijuana is considered a schedule I illegal controlled substance, and yet you can get Marinol for a known medical benefit.

A pt who is in your office who has missed their opiate dose (heroin, methadone, whatever the narcotic) tends to show anxiety, is disoriented, have cravings… they may ask for

Vicodin as part of the drug seeking behavior. Other symptoms of opiate withdrawal include sleep disturbance, nausea and vomiting, lacrimation, rhinorrhea, yawning, piloerection and gooseflesh, sweating, diarrhea, mydriasis (pupil dilation), abdominal cramping, hyperpyrexia, tachycardia and hypertension. If a good number of these symptoms are occurring, it can indicate the beginnings of opiate withdrawal.

When a pt withdraws from a benzodiazepine (schedule IV controlled substance, less addiction potential) it is typically less severe, but includes many of the things that we see with opiate withdrawal. There is not much difference between withdrawal from an opiate or a depressant.

The term “psychological dependence” is often used interchangeable with “habituation”. There are many pts who must take their meds regularly; a type I diabetic must take insulin regularly, but they are not abusing it nor dependent on it. Many otc drugs have a warning that they may be habit forming.

What is the difference between a benzodiazepine vs a barbiturate vs ethanol with respect to respiratory death? It has to do with the dose response curve. Notice the very flat dose-response curve associated with benzodiazepines. The dose used to produce anti-anxiety effects, sedation, and anti-convulsant effect is very low compared to the dose required to produce acute toxic effects or coma or worse. The barbiturates, conversely, are very dangerous because slight overdose can cause death by respiratory failure.

The vertical axis is cocaine “high” (correctly referred to by pharmacologists as “euphoria”). The effect is related to the dopaminergic pathway in the brain. Although cocaine is a viable local anesthetic and is a good vasoconstrictor, addicts are not seeking these results. The quickest euphoric effects come from smoking it, injecting it, or sniffing it.

Cannibis has been debated widely as to whether it has legitimate medicinal use. It produces drowsiness, perceptual change, and impairs task performance (including driving) so it continues to be defined as a schedule I controlled substance.

Category: Pharmacology Notes