How Different Types of Drugs Work

These very brief explanations of drug activity are intended to be read in conjunction with the more complete drug descriptions given on our main drug pages.

What are Anxiolytics and Why are They Used?

Anxiolytics (sometimes incorrectly called ‘minor tranquillisers’), are used primarily as ‘calmers’.

Anxiolytics are often prescribed to treat (but not to cure) general symptoms of anxiety as well as panic disorder, with or without agoraphobia. Drugs in this group also act as muscle relaxants and are sometimes used in the treatment of epilepsy.

How Do Anxiolytics Work?

These medications are thought to work primarily by enhancing the effects of the neurotransmitter GABA. This neurotransmitter promotes feelings of calmness. However, the full mechanisms of action for these drugs are not entirely understood.

What are Hynotics and Why are They Used?

Hypnotics (sleeping tablets) are widely prescribed for insomnia, or difficulty in getting to sleep or staying asleep.

Hypnotics cause sleepiness and are used as a short term treatment of insomnia. Some, such as chlormethiazole (‘Heminevrin’) can also be used to help agitation and restlessness, as well as to help ease withdrawal symptoms from alcohol. Insomnia is itself not an illness, but it can cause distress and potentially worsen some forms of psychological distress such as mania.

How Do Hypnotics Work?

Hypnotics help to calm you down and can make you sleepy, particularly if you are also suffering from anxiousness. Zopiclone and zolpidem both work on the same receptors as benzodiazepines, but with a short duration of action.

What are the Hypnotics?

Some commonly used hypnotics include:

Drugs

Available

Brand

name(s)

Forms available

Tablets

Capsules

Liquid

Injection

Chloral hydrate      

Yes

 
Chloral betaine Welldorm

Yes

 

Yes

 
Clomethiazole or chlomethiazole Heminevrin  

Yes

Yes

(sugar-free)

 

 

Diphenhydramine Nytol, Medinex

Yes

 

Yes

 
Promethazine Phenergan, Sominex,

Q-Mazine

Yes

 

Yes

Yes

Zaleplon Sonata  

Yes

   
Zolpidem Ambien,

Stilnoct

Yes

     
Zopiclone Zimovane, Zileze

Yes

     

 

What are Atypical Antipsychotics and Why are They Used?

Atypical antipsychotics, or neuroleptics (sometimes incorrectly called ‘major tranquillisers’), are used primarily in the treatment of psychosis and schizophrenia.

Antipsychotics are prescribed mainly in the treatment of psychosis and schizophrenia, although increasingly they are also being prescribed in the treatment of mania or hypomania.

How Do Atypical Antipsychotics Work?

These medications are thought to work primarily by reducing the effects of the neurotransmitter dopamine (by blocking some dopamine receptors), an excess of which is thought to produce some of the effects of the disorders they are used to treat — or by reducing the effects of dopamine together with serotonin (5-HT). The medications also have some effects on other neurotransmitter systems, including histamine, and Olanzapine’s (Zyprexa’s) actions include antagonism of muscarinic receptors and adrenergic receptors. However, the full mechanisms of action for these drugs are not entirely understood.

Additional Information

For important additional information about risks posed by anti-psychotics or neuroleptics, please see the pages on:

What is a Selective Norepinephrine Reuptake Inhibitor and Why are They Used?

Selective Norepinephrine Reuptake Inhibitors (SNRIs) are prescribed primarily for Attention-Deficit/Hyperactivity Disorder (ADHD).

Although the mechanism of action would seem also to relate to depression, the SNRI Atomoxetine (Strattera) is prescribed primarily for the treatment of Attention-Deficit/Hyperactivity Disorder (ADHD).

How Does a Selective Norepinephrine Reuptake Inhibitor Work?

The action of the SNRI Atomoxetine (Strattera) is thought to be related to selective inhibition of the pre-synaptic norepinephrine transporter, but its full mechanism of action is not understood.

Note that the acronym ‘SNRI’ is also sometimes used to denote ‘Serotonin-Norepinephrine Reuptake Inhibitor’; the similarity can easily cause confusion!

What are SSRIs and Why are They Used?

Selective Serotonin Reuptake Inhibitors (SSRIs), sometimes called 5-HT re-uptake blockers, are used primarily as anti-depressants.

SSRIs are among the most frequently prescribed medications for clients suffering from depression, but they have also been used to treat the eating disorder bulimia nervosa, anxiety (usually at lower doses), social phobia and social anxiety, obsessive-compulsive disorder, post-traumatic stress disorder, panic, pre-menstrual syndrome and agoraphobia. Some SSRI drugs are specifically “licensed” only for a subset of these conditions.

How Do SSRIs Work?

SSRIs increase the available amount of the neurotransmitter serotonin (also called 5-HT) in the brain by blocking its uptake into platelets and/or neurons (depending on the specific drug). In the brain, serotonin is thought to influence mood, emotions, the sleep/wake cycle and temperature regulation. (It also influences blood pressure and the digestive tract, and in fact the majority of the body’s serotonin is to be found in the ‘enteric brain’, the neural system of the digestive system.) Because low levels of serotonin are associated with depression and drowsiness, it is thought that by increasing the available amount of the neurotransmitter, SSRIs can help clients suffering from depression. However, the full mechanisms of the medication’s action are not entirely understood.

What is a Serotonin-Norepinephrine Reuptake Inhibitor and Why is it Used?

Venlafaxine (Effexor, Efexor), described at greater length on the Venlafaxine page, is a structurally novel anti-depressant called a Serotonin-Norepinephrine Reuptake Inhibitor.

Venlafaxine, a Serotonin-Norepinephrine Reuptake Inhibitor, is a structurally novel anti-depressant prescribed to treat depression, generalized anxiety disorder, and social anxiety disorder (social phobia).

How Does a Serotonin-Norepinephrine Reuptake Inhibitor Work?

Venlafaxine is thought to work by strongly inhibiting the reuptake of the neurotransmitters serotonin (or 5-HT) and norepinephrine (also called noradrenaline in the United Kingdom) and weakly inhibiting the reuptake of the neurotransmitter dopamine. It is thought that by increasing the available amount of these neurotransmitters, Venlafaxine can help individuals suffering from depression. However, the medication’s full mechanisms of action are not entirely understood.

Note that Serotonin-Norepinephrine Reuptake Inhibitor makes an acronym, ‘SNRI’, which is more commonly used to denote ‘Selective Norepinephrine Reuptake Inhibitor’; the similarity can easily cause confusion!

What is Nefazodone Used and Why is it Used?

Nefazodone, described at greater length on the Nefazodone (Serzone, Dutonin) page, is a structurally novel anti-depressant prescribed for the treatment of depression.

How Does Nefazodone Work?

Nefazodone (Serzone, Dutonin) is thought to work by inhibiting neuronal uptake of serotonin and norepinephrine. It is thought that by increasing the available amount of these neurotransmitters, Nefazodone can help individuals suffering from depression. However, the medication’s full mechanisms of action are not entirely understood.

What is Bupropion and Why is it Used?

Bupropion (Wellbutrin, Zyban), described at greater length on the Bupropion page, is a structurally novel anti-depressant prescribed to treat depression, generalized anxiety disorder, and social anxiety disorder (social phobia).

How Does Bupropion Work?

Bupropion acts as a relatively weak inhibitor of the neuronal uptake of norepinephrine (also called noradrenaline in the United Kingdom), serotonin, and dopamine, and it does not inhibit monoamine oxidase. Bupropion’s action as an anti-depressant is thought to be related to its effects on the noradrenergic and/or dopaminergic systems within the brain. However, its full mechanism of action is not entirely understood.

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