Drugs of Abuse - Part 2 PDF

Drugs of Abuse – Part 2 Presented by: Karishma Jeeboo, RPh., PharmD. Learning Outcomes Define and Define and explain drug abuse, tolerance, physical dependence, psychological explain dependence and addiction. Discuss the pharmacological effects of the drugs of abuse on the r...

Drugs of Abuse – Part 2 Presented by: Karishma Jeeboo, RPh., PharmD. Learning Outcomes Define and Define and explain drug abuse, tolerance, physical dependence, psychological explain dependence and addiction. Discuss the pharmacological effects of the drugs of abuse on the reward centre of the Discuss limbic areas of the brain. Explain the physiological basis of withdrawal symptoms after discontinued use of drug Explain abuse. Discuss the pharmacology of selected categories of drugs that are used for the treatment Discuss of the toxic effects of opiates, cocaine, benzodiazepines and other hypnotic drugs.  Ethanol, barbiturates, benzodiazepines (BDZs) BDZs commonly prescribed for anxiety; schedule IV; judged as low abuse liability. Short-acting BDZs like alprazolam have SEDATIVE- high addiction potential when used long- HYPNOTIC term DRUGS Same for short-acting barbiturates – secobarbital. Ethanol is not listed on the schedule of controlled substances with abuse liability – however, clearly heavily abused. SEDATIVE-HYPNOTIC DRUGS Reduce inhibitions, suppress anxiety and produce relaxation. These actions are thought to encourage repetitive use. Primary actions – facilitates the effects of GABA, antagonises cholinergic nicotinic receptors Also enhances brain dopaminergic pathways – perhaps this the most related to addiction. CNS depressants, which are enhanced by concomitant use of ethanol, opioids, analgesics, antipsychotic agents, marijuana and other drugs with sedative properties. SEDATIVE-HYPNOTIC DRUGS Acute overdoses commonly result in death Depression of the medullary respiratory and cardiovascular centres. Management of OD – maintenance of patient airway and ventilatory support Flumazenil is used to reverse the CNS depressant effects of BDZs. No antidote for barbiturates or ethanol Flunitrazepam (Rohypnol) potent rapid onset BDZ with amnestic properties – used in ‘date rape” Added to alcoholic beverages, chloral hydrate or GHB in sufficient doses also renders the victim incapable of resisting rape. Opioid Analgesics For pharmacologic action, opioids act mainly on opioid receptors However, other actions, including disinhibition of dopaminergic pathways in the CNS Most commonly abused drugs: Heroin Morphine Codeine Oxycodone, hydrocodone, hydromorphone Meperidine Fentanyl Opioid Analgesics Effects of IV heroin are described as a ‘rush’ or organic feeling followed by euphoria and then sedation. IV administration of opioids is associated with rapid development of tolerance, dependence and addiction. Oral administration/smoking – milder effects; slower onset of tolerance and dependence. Yet, the High efficacy of fentanyl, its abundance and its low cost have resulted in a fentanyl crisis. OD of opioids – respiratory depression, coma and death. Opioid Analgesics OD is managed with parenteral naloxone or nalmefene and ventilatory support. Kratom, a crude plant extract, has poorly defined opioid effects but has been misused since it is available as a botanical OTC. Opioid Anagesics Withdrawal effects of opioids (abstinence syndrome) – lacrimation, rhinorrhea, yawning, sweating, weakness, gooseflesh (‘cold turkey’), nausea, vomiting, tremor, muscle jerks. Treatment includes replacement of the illicit drug with a pharmacologically active equivalent agent, e.g. methadone, followed by slow dose reduction. Buprenorphine, a partial agonist at µ-receptors and a longer- acting opioid (t1/2 >40hrs) is also used for withdrawal symptoms and substitution therapy for opioid addicts. STIMULANTS – Amphetamines Alter amine transporter activity in the CNS – dopamine, norepinephrine and serotonin – can increase their release. Feeling of euphoria and self-confidence contributes to the rapid development of addiction Drugs include: Dextroamphetamine Methamphetamine (‘speed’), a crystal form (“ice’) can be smoked. Chronic high-dose abuse leads to a psychotic state – delusions and paranoia. STIMULANTS – Amphetamines Symptoms of overdose – agitation, restlessness, tachycardia, hyperthermia, hyperreflexia and possible seizures. No antidote; supportive care – control of body temperature, protection against cardiac arrhythmias and seizures. Tolerance can be marked – withdrawal symptoms characterised by increased appetite, sleepiness, exhaustion, and mental depression. congeners of amphetamines – 2,5-dimethoxy-4-methylamphetamine (DOM[STP]), dioxymethaphetamines (MDA), methylene dioxymethaphetamines (MDMA, ecstasy) MDMA – selective serotonin transporter in the CNS – purported to facilitate interpersonal communication and act as a sexual enhancer. Hallucinogens Phencyclidine (PCP) (‘angel dust’) and ketamine (‘special K’) – antagonists at the glutamate NMDA receptor. They have no action on dopaminergic neurons in the brain Psychotic reactions are common with PCP; impaired judgement, which often leads to reckless behaviour. Overdose with PCP – horizontal and vertical nystagmus, marked HTN, and seizures which may be fatal. Perenteral BDZs (diazepam, lorazepam) used to curb excitation and protect against seizures. Hallucinogens Other drugs having hallucinogenic effects have abuse potential – lysergic acid diethylamide (LSD), mescaline, psilocybin. Scopolamine and other muscarinic agents may have this potential Act on serotonin receptors and indirectly increase glutamate receptor release in the CNS – they do not have dependence and do not act on dopaminergic pathways. Terms used to describe these drugs – psychedelic and mind revealing. Marijuana Marijuana (‘grass’ or ‘pot’)- collective term for the psychoactive constituents in crude extracts of the plant Cannabis sativa and Cannabis indica. Active principles, which include the cannabinoid compounds – tetrahydrocannabinol (THC), cannabidiol (CBD) and cannabinol (CBN). Cannabis sativa has further subspecies – hemp plant (low levels of THC and high levels of CBD) and medical marijuana flowering/bud plants, which tend to have higher levels of THC vs CBD levels. Hashish is partially purified THC-containing material that is more potent. Cannabinoids Endogenous cannabinoids in the CNS – anandamide and 2- arachidonyl glycerol – are released postsynaptically and act as retrograde messengers to inhibit presynaptic release of conventional transmitters like dopamine. The receptors for these endogenous compounds are thought to be the targets for exogeneous cannabinoids present in marijuana. Effects of Marijuana CNS effects of marijuana – feeling of being “high” with euphoria, disinhibition, uncontrollable laughter, changes in perception, and achievement of a dream-like state. These effects – THC on the cannabinoid type-1 (CB1) receptor. Mental concentration is difficult Vasodilation and pulse rate increases. Habitual users show reddened conjunctiva Withdrawal states are noted in heavy users. Effects Marijuana Dangers – impairment of judgement and reflexes Effects are potentiated by concomitant use of sedative-hypnotics, including ethanol Chronic use had implications for cognitive impairment, cannabis use disorder and hyperemesis. Perceived risk of automobile accidents – roadside tests “driving while high” Potential therapeutic effects – ability to decrease intraocular pressure, analgesic effects, antiemetic action. Preparations Dronabinol – a controlled-substance formulation of THC and nabilone (a synthetic analogue of THC) - used to combat severe nausea and as an adjunct for chronic pain. Nabiximols (Sativex) –botanical drug composed of THC and CBD. CBD has recently been approved for specific types of epilepsy but lacks any addictive properties. Rimonabant – inverse agonist at CB1 receptors was approved for use for treatment of obesity in Europe but has been withdrawn. Inhalants Certain gases or volatile liquids are abused because they provide a feeling of euphoria and disinhibition Anesthetics – nitrous oxide, chloroform, diethyl ether. Affect judgement and induce loss of consciousness. Inhalation of nitrous oxide as a pure gas (without oxygen) has caused asphyxia and death. Inhalants Industrial Solvents—Solvents and a wide range of volatile compounds are present in commercial products, such as gasoline, paint thinners, aerosol propellants, glues, rubber cement, and shoe polish. Active ingredients – benzene, hexane, methylethylketone, toluene, and trichloroethylene. May of these compounds – toxic to the liver, kidneys, lungs, bone marrow, and peripheral nerves. Inhalants Organic Nitrates Amyl nitrate, isobutyl nitrite and other organic nitrites referred to as “poppers” – used as sexual intercourse enhancers. Inhalation of nitrites caused dizziness, tachycardia, hypertension and flushing. Steroids In many countries, including the USA, anabolic steroids are controlled substances based on their potential for abuse. Effects sought by abusers are increase in muscle mass and strength rather than euphoria. Excessive use – adverse behavioural, CV (MI), and musculoskeletal effects. Acne (sometimes severe) and masculinisation in females are anticipated androgenic adverse effects. Hepatic dysfunction has been reported Behavioural manifestations – increases in libido and aggression (“roid rage”) Withdrawal syndrome – fatigue and depression of mood.