CITAZEPAM

Indications

• All forms of epilepsy
• Myoclonus
• Panic disorders (with or without agoraphobia) resistant to antidepressant therapy

Dosage

Children: Child 1–11 months: Initially 250 micrograms once daily for 4 nights, dose to be increased over 2–4 weeks, usual dose 0.5–1 mg daily, taken at night; may be given in 3 divided doses if necessary.

Adults: Initially 1 mg once daily for 4 nights, dose to be increased over 2–4 weeks, usual dose 4–8 mg daily, adjusted according to response.

Mechanism of action

Clonazepam binds to benzodiazepine receptors associated with GABA(a) receptors in the central nervous system. This binding increases the affinity of GABA for its receptor, enhancing chloride ion conduction across neuronal membranes. The resultant hyperpolarization of the neuron decreases its excitability, leading to reduced neuronal firing and contributing to its anticonvulsant effects.

Pharmacodynamics

Clonazepam exhibits common pharmacodynamic properties of benzodiazepines, including anticonvulsive, anxiolytic, sedative, and muscle relaxant effects. It effectively suppresses various types of paroxysmal activity in the brain, including generalized spike-wave discharges in absence seizures and minor motor seizures. It is particularly effective in reducing generalized EEG abnormalities.

Pharmacokinetics

Clonazepam is well absorbed after oral administration, with peak plasma concentrations typically reached within 1-4 hours. It is metabolized primarily in the liver and has a half-life ranging from 18 to 50 hours, allowing for once-daily dosing in many cases. The drug's effects can persist for several hours due to its active metabolites.

Contra-indications

• Coma
• Current alcohol abuse
• Current drug abuse
• Respiratory depression
• Acute porphyrias
• Severe airway obstruction

Adverse effects

• Alopecia
• Increased bronchial secretions (in children)
• Impaired coordination
• Abnormal drooling (in children)
• Gastrointestinal disorders
• Hypersalivation (in children)
• Incomplete precocious puberty

Interactions

• Nevirapine may decrease clonazepam concentration

Precautions

• Caution in patients with depression
• Caution in patients with spinal ataxia
• Monitor for decreased effectiveness after prolonged use

Pregnancy

Clonazepam should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. It is associated with risks of congenital malformations when taken in the first trimester.

Breast-feeding

Clonazepam is excreted in breast milk; caution is advised when administering to nursing mothers.

Storage

Store in a cool, dry place away from light. Keep out of reach of children.

Formulations

• Clonazepam 0.5 mg tablet
• Clonazepam 1 mg tablet
• Clonazepam 2 mg tablet
• Clonazepam oral suspension (various concentrations)

Indications

• Depressive illness
• Generalized anxiety disorder
• Obsessive-compulsive disorder
• Panic disorder
• Social anxiety disorder

Mechanism of action

Escitalopram enhances serotonergic activity by binding to the primary binding site on the serotonin transporter (SERT), preventing the re-uptake of serotonin into the presynaptic neuron. It also acts as an allosteric serotonin re-uptake inhibitor, binding to a secondary allosteric site on SERT to more effectively inhibit serotonin re-uptake, leading to elevated extracellular serotonin levels. This sustained increase eventually desensitizes 5-HT1A auto-receptors, which is critical for the full clinical effect of SSRIs.

Pharmacodynamics

As a selective serotonin re-uptake inhibitor, escitalopram increases serotonin levels in neuronal synapses, leading to an antidepressant effect. Compared to other SSRIs, escitalopram has a relatively quick onset of action due to its potency. The drug has been associated with potential adverse effects such as abnormal bleeding and serotonin syndrome, particularly when used with other serotonergic drugs. Abrupt discontinuation may lead to withdrawal symptoms, necessitating a gradual tapering of the dose.

Pharmacokinetics

Escitalopram is well absorbed after oral administration, with peak plasma concentrations typically reached within 4-6 hours. It has a volume of distribution of approximately 12 L/kg and is highly protein-bound. The drug undergoes extensive hepatic metabolism, primarily via the cytochrome P450 enzyme CYP2C19, and has a half-life of about 27-32 hours, allowing for once-daily dosing. Renal impairment does not significantly affect the pharmacokinetics of escitalopram, but caution is advised in hepatic impairment.

Contra-indications

• QT-interval prolongation
• concurrent use of monoamine oxidase inhibitors (MAOIs)
• hypersensitivity to escitalopram or any of its excipients

Adverse effects

• nausea
• somnolence
• insomnia
• dry mouth
• sweating
• dizziness
• sexual dysfunction
• increased risk of bleeding
• serotonin syndrome

Interactions

• moclobemide + escitalopram: Moderate (increases exposure)
• other serotonergic drugs (risk of serotonin syndrome)
• anticoagulants (increased risk of bleeding)

Precautions

• use with caution in patients with a history of seizures
• monitor for signs of serotonin syndrome
• gradual tapering recommended to avoid discontinuation syndrome
• consider risks in patients with hepatic impairment

Pregnancy

Escitalopram should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Data suggest potential risks including fetal cardiac defects.

Breast-feeding

Present in breast milk; use with caution and consider alternative treatments if necessary.

Storage

Store at room temperature, away from moisture and heat. Keep container tightly closed.

Formulations

• Citalopram 40 mg/ml oral drops, sugar-free
• Citalopram 10 mg tablets
• Citalopram 20 mg tablets
• Citalopram 40 mg tablets

Indications

• Management of hyperoxaluria
• Prevention of calcium oxalate kidney stones
• Assessment of metabolic disorders related to oxalate

Dosage

Children: Refer to the BNF for Children for specific dosing guidelines.

Adults: Refer to the BNF for specific dosing guidelines.

Mechanism of action

Oxalate primarily functions as a metabolic byproduct in various pathways. It is involved in the superpathway of glycolysis and the tricarboxylic acid (TCA) cycle. In plants, oxalate can play a part in regulating calcium levels and can affect the solubility of calcium and other minerals, influencing mineral absorption. In humans, high levels of oxalate can lead to the formation of insoluble calcium oxalate crystals, contributing to kidney stone formation.

Pharmacodynamics

Oxalate interacts with calcium in the body, leading to the formation of calcium oxalate, which is poorly soluble. This property is critical in the context of kidney stone formation, as elevated oxalate levels can increase the risk of crystallization and subsequent stone development. The balance of oxalate in the body is influenced by dietary intake, metabolic processes, and renal excretion.

Pharmacokinetics

Oxalate is absorbed from the gastrointestinal tract and is also produced endogenously. Once in the bloodstream, it is primarily excreted by the kidneys. The renal clearance of oxalate is significant, and reduced kidney function can lead to elevated serum and urine oxalate levels, increasing the risk for stone formation. Factors such as hydration, dietary oxalate, and calcium intake can influence oxalate metabolism and excretion.

Pregnancy

There is no specific information available regarding the use of oxalate during pregnancy.

Breast-feeding

There is no specific information available regarding the use of oxalate during breastfeeding.

Storage

Store in a cool, dry place away from direct sunlight.

Formulations

• {'formulation': 'Oxalate salt', 'description': 'Used in various formulations, particularly in laboratory and industrial applications.'}

Mechanism of action

Gamma-Aminobutyric acid (GABA) is considered the principal inhibitory neurotransmitter in the human body. When GABA binds to GABA(a) receptors found in neuron synapses, chloride ions are conducted across neuron cell membranes via an ion channel in the receptors. With enough chloride ions conducted, the local, associated neuron membrane potentials are hyperpolarized - making it more difficult or less likely for action potentials to fire, ultimately resulting in less excitation of the neurons. Subsequently, benzodiazepines like clonazepam can bind to benzodiazepine receptors that are components of various varieties of GABA(a) receptors. This binding acts to enhance the effects of GABA by increasing GABA affinity for the GABA(a) receptor, which ultimately enhances GABA ligand binding at the receptors. This enhanced ligand binding of the inhibitory neurotransmitter GABA to the receptors increases the aforementioned chloride ion conduction (perhaps reportedly via an increase in the frequency of the chloride channel opening), resulting in a hyperpolarized cell membrane that prevents further excitation of the associated neuron cells. Combined with the notion that such benzodiazepine receptor associated GABA(a) receptors exist both peripherally and in the CNS, this activity consequently facilitates various effects like sedation, hypnosis, skeletal muscle relaxation, anticonvulsant activity, and anxiolytic action. In particular, when out of the ordinary rapid and repetitive electrical signals are released in the CNS, it is proposed that the brain can become over-stimulated and ordinary functions are disrupted - resulting in seizure activity. By enhancing the neuro-inhibitory activity of GABA, it is believed that clonazepam can facilitate in decreasing any excessive electrical nerve activity in the CNS that might be contributing to seizures. Concurrently, it is also believed that clonazepam's actions in enhancing GABA effects may inhibit neuronal activity proposed to occur in amygdala-centered fear circuits - therefore assisting in the management of anxiety or panic.

Pharmacodynamics

The pharmacodynamic properties of clonazepam are common among benzodiazepines and include anticonvulsive, sedative, muscle relaxing and anxiolytic effects. Animal data and electroencephalographic investigations in man have shown that clonazepam rapidly suppresses many types of paroxysmal activity including the spike and wave discharge in absence seizures (petit mal), slow spike wave, generalized spike wave, spikes with temporal or other locations, as well as irregular spikes and waves. Moreover, the agent can also decrease the frequency, amplitude, duration, and spread of discharge in minor motor seizures. Generalized EEG abnormalities are more readily suppressed by clonazepam than are focal EEG abnormalities such as focal spikes. Clonazepam has beneficial effects in generalized and focal epilepsies.

Mechanism of action

Escitalopram, like other selective serotonin re-uptake inhibitors, enhances serotonergic activity by binding to the orthosteric (i.e. primary) binding site on the serotonin transporter (SERT), the same site to which endogenous 5-HT binds, and thus prevents the re-uptake of serotonin into the presynaptic neuron. Escitalopram, along with [paroxetine], is also considered an allosteric serotonin re-uptake inhibitor - it binds to a secondary allosteric site on the SERT molecule to more strongly inhibit 5-HT re-uptake. Its combination of orthosteric and allosteric activity on SERT allows for greater extracellular 5-HT levels, a faster onset of action, and greater efficacy as compared to other SSRIs. The sustained elevation of synaptic 5-HT eventually causes desensitization of 5-HT_1A auto-receptors, which normally shut down endogenous 5-HT release in the presence of excess 5-HT - this desensitization may be necessary for the full clinical effect of SSRIs and may be responsible for their typically prolonged onset of action. Escitalopram has shown little-to-no binding affinity at a number of other receptors, such as histamine and muscarinic receptors, and minor activity at these off-targets may explain some of its adverse effects. The mechanism of antidepressant action of escitalopram, the S-enantiomer of racemic citalopram, is presumed to be linked to potentiation of serotonergic activity in the central nervous system (CNS) resulting from its inhibition of CNS neuronal reuptake of serotonin (5-HT).

Pharmacodynamics

Escitalopram belongs to a class of medications called selective serotonin re-uptake inhibitors (SSRIs). These agents cause an increase in serotonin levels in neuronal synapses by preventing the re-uptake of serotonin (5-HT) into the presynaptic terminals of serotonergic neurons. As compared to other SSRIs, it appears to have a relatively quick onset of effect due to its potency. SSRIs as a class have been associated with abnormal bleeding, particularly in patients receiving concomitant therapy with other medications affecting hemostasis, and with the development of serotonin syndrome. Use escitalopram with caution in patients with a higher-than-baseline risk of bleeding and in patients receiving concomitant therapy with other serotonergic drugs. Escitalopram may also cause a discontinuation syndrome with abrupt removal of the drug, and should be slowly tapered if discontinuation of therapy is warranted.