What is/are Midazolam?
Midazolam (/mɪˈdæzəlæm/, marketed in English-speaking countries under the trade names Dormicum, Hypnovel, and Versed,) is a short-acting drug in the benzodiazepine class developed by Hoffmann-La Roche in the 1970s. The drug is used for treatment of acute seizures, moderate to severe insomnia, and for inducing sedation and amnesia before medical procedures. It possesses profoundly potent anxiolytic, amnestic, hypnotic, anticonvulsant, skeletal muscle relaxant, and sedative properties. Midazolam has a fast recovery time and is the most commonly used benzodiazepine as a premedication for sedation; less commonly it is used for induction and maintenance of anesthesia. Flumazenil, a benzodiazepine antagonist drug, can be used to treat an overdose of midazolam, as well as to reverse sedation. However, flumazenil can trigger seizures in mixed overdoses and in benzodiazepine-dependent individuals, so is not used in most cases.
Administration of midazolam by the intranasal or the buccal route (absorption via the gums and cheek) as an alternative to rectally administered diazepam is becoming increasingly popular for the emergency treatment of seizures in children. Midazolam is also used for endoscopy procedural sedation and sedation in intensive care. The anterograde amnesia property of midazolam is useful for premedication before surgery to inhibit unpleasant memories. Midazolam, like many other benzodiazepines, has a rapid onset of action, high effectiveness and low toxicity level. Drawbacks of midazolam include drug interactions, tolerance, and withdrawal syndrome, as well as adverse events including cognitive impairment and sedation. Paradoxical effects occasionally occur, most commonly in children and the elderly, particularly after intravenous administration.
Side effects of midazolam in the elderly are listed above. People experiencing amnesia as a side effect of midazolam are generally unaware their memory is impaired, unless they had previously known it as a side affect
Long-term use of benzodiazepines has been associated with long-lasting deficits of memory, and show only partial recovery six months after stopping benzodiazepines. It is unclear whether full recovery occurs after longer periods of abstinence. Benzodiazepines can cause or worsen depression. Paradoxical excitement occasionally occurs with benzodiazepines, including a worsening of seizures. Children and elderly individuals or those with a history of alcohol abuse and individuals with a history of aggressive behavior or anger are at increased risk of paradoxical effects. Paradoxical reactions are particularly associated with intravenous administration. After nighttime administration of midazolam, residual 'hangover' effects, such as sleepiness and impaired psychomotor and cognitive functions, may persist into the next day. This may impair the ability of users to drive safely and may increase the risk of falls and hip fractures. Sedation, respiratory depression and hypotension due to a reduction in systematic vascular resistance, and an increase in heart rate can occur. If IV midazolam is given too quickly, hypotension may occur. A “midazolam infusion syndrome” may result from high doses, and is characterised by delayed arousal hours to days after discontinuation of midazolam, and may lead to an increase in the length of ventilatory support needed.
In susceptible individuals, midazolam has been known to cause a paradoxical reaction, a well-documented complication with benzodiazapines. When this occurs, the individual may experience anxiety, involuntary movements, aggressive or violent behavior, uncontrollable crying or verbalization, and other similar effects. This seems to be related to the altered state of consciousness or disinhibition produced by the drug. Paradoxical behavior is often not recalled by the patient due to the amnesia-producing properties of the drug. In extreme situations, flumazenil can be administered to inhibit or reverse the effects of midazolam. Antipsychotic medications, such as haloperidol, have also been used for this purpose.
Midazolam is known to cause respiratory depression. In healthy humans, 0.15 mg/kg of midazolam may cause respiratory depression, which is postulated to be a central nervous system (CNS) effect. When midazolam is administered in combination with fentanyl, the incidence of hypoxemia or apnea becomes more likely.
Although the incidence of respiratory depression/arrest is low (0.1-0.5%) when midazolam is administered alone at normal doses, the concomitant use with CNS acting drugs, mainly analgesic opiates, may increase the possibility of hypotension, respiratory depression, respiratory arrest, and death, even at therapeutics doses. Potential drug interactions involving at least one CNS depressant were observed for 84% of midazolam users who were subsequently required to receive the benzodiazepine antagonist flumazenil. Therefore, efforts directed toward monitoring drug interactions and preventing injuries from midazolam administration are expected to have a substantial impact on the safe use of this drug.
Tolerance, dependence and withdrawal
A benzodiazepine dependence occurs in about one third of individuals who are treated with benzodiazepines for longer than 4 weeks, which typically results in tolerance and benzodiazepine withdrawal syndrome when the dose is reduced too rapidly. Midazolam infusions may induce tolerance and a withdrawal syndrome in a matter of days. The risk factors for dependence include dependent personality, use of a benzodiazepine which is short-acting, high potency and long-term use of benzodiazepines. Withdrawal symptoms from midazolam can range from insomnia and anxiety to seizures and psychosis. Withdrawal symptoms can sometimes resemble a persons underlying condition. Gradual reduction of midazolam after regular use can minimise withdrawal and rebound effects. Tolerance and the resultant withdrawal syndrome may be due to receptor down-regulation and GABAA receptor alterations in gene expression which results in long-term changes in the function of the GABAergic neuronal system.
Chronic users of benzodiazepine medication who are given midazolam experience reduced therapeutic effects of midazolam, due to tolerance to benzodiazepines. Prolonged infusions with midazolam results in the development of tolerance; if midazolam is given for a few days or more a withdrawal syndrome can occur. Therefore in order to prevent a withdrawal syndrome a prolonged infusion needs to be gradually withdrawn and sometimes if necessary continued tapering of dose with an oral long-acting benzodiazepine such as clorazepate dipotassium. When signs of tolerance to midazolam occur during intensive care unit sedation the addition of an opioid or propofol is recommended. Withdrawal symptoms can include irritability, abnormal reflexes, tremors, clonus, hypertonicity, delirium, and seizures, nausea, vomiting and diarrhea, tachycardia, hypertension and tachypnea.
A midazolam overdose is considered a medical emergency and generally requires the immediate attention of medical personnel. Benzodiazepine overdose in healthy individuals is rarely life threatening with proper medical support; however, the toxicity of benzodiazepines increases when they are combined with other CNS depressants such as alcohol, opioids, or tricyclic antidepressants. The toxicity of benzodiazepine overdose and risk of death is also increased in the elderly and those with obstructive pulmonary disease or when used intravenously. Treatment is supportive; activated charcoal can be used within an hour of the overdose. The antidote for an overdose of midazolam (or any other benzodiazepine) is flumazenil (Anexate). While effective in reversing the effects of benzodiazepines it is not used in most cases as it may trigger seizures in mixed overdoses and benzodiazepine dependent individuals.
Symptoms of midazolam overdose can include:
- Slurred speech
- Somnolence (difficulty staying awake)
- Mental confusion
- Respiratory arrest
- Vasomotor collapse
Impaired motor functions
- Impaired reflexes
- Impaired coordination
- Impaired balance
Detection in body fluids
The concentrations of midazolam and/or its major metabolite, 1-hydroxymidazolam glucuronide, may be quantified in plasma, serum or whole blood in order to monitor for safety in those receiving the drug therapeutically, to confirm a diagnosis of poisoning in hospitalized patients or to assist in a forensic investigation of a case of fatal overdosage. Patients with renal dysfunction may exhibit prolongation of elimination half-life for both the parent drug and its active metabolite, with accumulation of these two substances in the bloodstream and the appearance of adverse depressant effects.
HIV protease inhibitors, nefazodone, sertraline, grapefruit juice, fluoxetine, erythromycin, diltiazem, clarithromycin inhibit the metabolism of midazolam, leading to a prolonged action. St John's wort, rifapentine, rifampin, rifabutin, phenytoin enhance the metabolism of midazolam leading to a reduced action. Sedating antidepressants, antiepileptic drugs such as phenobarbital, phenytoin and carbamazepine, sedative antihistamines, opiates, antipsychotics and alcohol enhance the sedative effects of midazolam. Midazolam is metabolized almost completely by cytochrome P450-3A4. Atorvastatin administration along with midazolam results in a reduced elimination rate of midazolam. St John's wort decreases the blood levels of midazolam. Grapefruit juice reduces intestinal 3A4 and results in less metabolism and higher plasma concentrations.
This article uses material from the Wikipedia article Midazolam, which is released under the Creative Commons Attribution-Share-Alike License 3.0.