Category: 08. Drugs Acting In The Central Nervous System

Local anesthetics are either esters (procaine, dibucaine, benzocaine, etc) or amides (lidocaine, prilocaine, bupivacaine, etc). The ester containing compounds are usually inactivated in the plasma and tissues by non-specific esterases. Local anesthetics block the initiation of action potentials by preventing the voltage-dependant increase in Na+ conductance. Local anesthetics are used in minor surgery, dentistry, abdominal…

As compared to CNS depressants the stimulants of the centeral nervous system are therapeutically not so useful as they lack selectivity of action. Further, excessive stimulation of CNS is followed by its depression. CNS stimulant can be classified into convulsants and respiratory stimulants eg. Srychnine picrotoxin, nikethaimide psychomotor stimulants Eg. Amphetamine, cocaine, caffeine psychotomimetic drug…

Opioid Analgesics Opioid is any substance that can produce morphine like effects. Opium is an extract of the juice of the poppy Papaver somniferum. Opium contains many alkaloids related to morphine. The main group of drugs that are discussed in section are divided into two; morphine analogues and synthetic derivatives. Morphine analogues. Compounds closely related…

Depression is one of the most common psychic disorders. Antidepressants are the drugs which are mainly used in the management of depression. Types of antidepressant drugs Tricyclic antidepressants (TCAs) Monoamine oxidase inhibitors (MAOI) 5-HT uptake inhibitors Atypical antidepressants Pharmacokinetics Most tricyclics are incompletely absorbed and undergo significant first-pass metabolism. Highly protein bound and relatively high…

Psychotic illness is characterized by delusion, hallucinations, thought disorder, social withdrawal and flattering of emotional response. Antipsychotics are a group of drugs used mainly for treating schizophrenia. Antipsychotic agents are classified into typical neuroleptics (chlorpromazine, thioridazine, haloperidol, flupenthixol) and atypical neurolopitics (clozapine, sulpiride). Most antipsychotic drugs are readily but incompletely absorbed. Many of these drugs…

Antimuscarinic drugs have a number of central nervous system effects, including drowsiness, mental slowness, inattention, restlessness, and confusion, agitation, delusions, hallucinations, and mood changes. Other common effects include dryness of the mouth, blurring of vision, mydriasis, urinary retention, nausea and vomiting, constipation, tachycardia, tachypnea, increased intraocular pressure, palpitations, and cardiac arrhythmias. Contraindications: Acetylcholine-blocking drugs should…

Amantadine, an antiviral agent, was by chance found to have antiparkinsonism properties. Its mode of action in parkinsonism is unclear, but it may potentiate dopaminergic function by influencing the synthesis, release, or reuptake of dopamine. Acetylcholine Blocking Drugs (Benztropine, Trihexyphenidyl) A number of centrally acting antimuscarinic preparations are available that differ in their potency and…

The enzymes responsible for synthesizing dopamine are depleted in the brains of Parkinsonism patients, and drugs acting directly on dopamine receptors may therefore have a beneficial effect additional to that of levodopa. There are a number of dopamine agonists with antiparkinsonism activity. e.g: Bromocryptine Monoamine Oxidase Inhibitors: Selegiline (deprenyl), a selective inhibitor of monoamine oxidase…

Levodopa, the immediate metabolic precursor of dopamine, does penetrate the blood brain barrier, where it is decarboxylated to dopamine. Levodopa is rapidly absorbed from the small intestine. Food will delay the appearance of levodopa in the plasma. It is extensively metabolized by peripheral dopa decarboxylase, hence given in combination with carbidopa, a peripheral dopa decarboxylase…

Parkinsonism: Parkinsonism is characterized by a combination of rigidity, bradykinesia, tremor, and postural instability. It is due to the imbalance between the cholinergic and dopaminergic influences on the basal ganglia. Thus, the aim of the treatment is either to increase dopaminergic activity (by dopamine agonist) or to decrease cholinegic (antimuscarinic drugs) influence on the basal…