Drugs and their effects


Many people believe that it is very difficult to identify an individual who may be under the influence of a drug. However, with a basic understanding of the effects of specific categories of drug, this identification becomes far easier.

The following paragraphs give some basic observable signs and symptoms in finding individuals who may be impaired to drive or work and what category of drug they may be under the influence of.

Despite the fact that there are many hundreds of drugs that are available by prescription, over the counter or by illicit means, there are seven basic categories of drug that will identify specific signs and symptoms. The medical profession may call them by another name, but for the purposes of drug influence recognition these categories are:


Examples of drugs in these categories would include

1. Various types of Cannabis (Herbal, Resin, Oil etc)
2. Heroin
3. Cocaine
4. Alcohol, GHB, Prescription drugs such as Diazepam
5. LSD, Ecstasy
6. Solvents, Glue
7. Ketamine, PCP

The following paragraphs are only a very basic insight into influence recognition and there are many other factors that we are unable to cover here.


Cannabis can be grown in most parts of the world where temperate climates exist. It may affect the users ability to pay attention and has varying effects dependant upon the dose taken and tolerance to the drug. The main psychoactive ingredient in Cannabis is Delta9 Tetrahydrocannabinol. (THC).

Cannabis metabolises in the body to form specific metabolites (Carboxy and Hydroxy THC) only one of which, Hydroxy THC, is psychoactive. Carboxy THC is not believed to be psychoactive although this inactive metabolite can be found in the blood for up to 28/30 days after ingestion and can be found for a much longer period in the hair roots, up to 4 months. Cannabis is generally 80 times more carcinogenic than tobacco.Cannabis Grn

The following may be observed when a person is under the influence:

  • Particular smell
  • Poor coordination
  • Poor Balance
  • Impaired perception of time and distance
  • Disorientation
  • Poor attention span
  • Relaxed inhibitions
  • Red Sclera (eye whites)
  • Plant debris in mouth
  • Body & eyelid tremors
  • Possible paranoia
  • Confusion
  • Short term memory loss

Effects of the drug tend to peak after about 10 minutes and continue for 2-3 hours. However impairment may be present in the user for up to 24 hours without the knowledge of the individual. Pupils may be dilated, although these could be normal dependent upon the amount of THC ingested. The individual will also be unable to cross their eyes (Lack of convergence) and in high doses will cause an involuntary jerking movement of the eyes when the eyes are moved in the vertical plane (Gaze Nystagmus).


The Opium poppy is the main provider of all narcotic analgesics. There is very little use of Opium in its raw form today, there are many derivatives which are just as toxic. The main and most common derivative is Heroin. Originally it was used as a cough suppressant and pain relief, because an opiate based drug suppresses the cough reflex. It was sold openly by Bayer Pharmaceuticals in the 1940’s and 50’s and by chemists, pharmacists and Doctors, who frequently prescribed it for all manner of ailments. Now medicinal heroin (called diamorphine) is restricted to palliative, end of life care and other circumstances of extreme pain by doctors.

Heroin is the most potent of drugs available on the illicit market. It is extremely addictive and a user can become dependant upon it in the space of three to four uses. It has been described as like being wrapped in a warm blanket or sinking into a hot bath, all troubles being washed away.

What it actually does is prevent the production of the neurotransmitter, dopamine in the brain. The result of this is that the user becomes clinically addicted to the drug as opposed to being psychologically addicted. The difference of which is too complicated to discuss on this page. In other words the user cannot live without it. The damage, once done, can only be removed by a painful and tortuous journey through physical withdrawal symptoms, commonly known as ‘cold turkey’. 60% of all acquisitive crime is committed by heroin users in order for them to seek their next ‘hit’.

Generally the following may be observed when a person is under the influence:

  • Constricted (pinpoint) pupils
  • Sleepy appearance (Droopy eyelids)
  • Slow reflexes
  • Deep, slow speech
  • Facial itching
  • Dry mouth
  • Some possible euphoria
  • Cold skin
  • Nausea
  • Slow, deliberate movements
  • Calm sedate manner

If heroin is injected or smoked it will take effect within seconds, with visible effects appearing within 5 – 30 minutes. These effects continue for between 4 and 6 hours.

In addition to the physical signs of use, one of the most obvious signs is the paraphernalia used by the abuser. A heroin user requires certain things to be able to either inject or smoke the drug. The most obvious and distressing sign of heroin abuse however is pinpoint pupils, the users neglect of personal hygiene, and an overpowering need for the next hit to the exclusion of everything else, including food.

Central Nervous System Stimulants

There are many stimulant type drugs available on the illicit and over the counter market. Over the counter stimulants would include high caffeine drinks. Some highs regarded as ‘legal’ until recently were such drugs as BZP and Salvia Divornum.

The use of Amphetamine Sulphate in the UK has declined over the years, only to be replaced by Cocaine and crack Cocaine. Just recently the UK has seen an increase in the use of Methyl amphetamine (Meth, Ice, Crystal), a powerful stimulant that suppresses appetite and causes aggression.

The effects of Cocaine and Crack are relatively short lived and a user can present some difficulty in detection. It is a fast acting, short duration drug that is generally snorted or smoked. Cocaine acts on the Serotonin neurotransmitters of the brain, by flooding the synapses. This causes the user to be extremely active and gregarious.

Generally the following may be observed when a person is under the influence:

  • Dilated (Large) Pupils
  • Eyelid tremors
  • Restlessness
  • Anxiety
  • Very Talkative
  • Euphoric
  • Easily irritated
  • Grinding teeth (Bruxism)
  • Fast internal clock
  • Foul/rancid odour
  • Nervous movements
  • Burnt lips/fingers or gums (Amphetamines/Meth)
  • Runny Nose (Rhinitis) (Cocaine on the downside)

Cocaine use in the UK has significantly increased over the past few years, mainly due to the falling price of a gram. It is seen as the drug of choice for many professionals who, incorrectly, think that they are able to do business better while under its influence. As with all stimulants, their use only speed up the body’s metabolism and does not speed up the ability to learn or do things better!

Central Nervous System Depressants

Of all the categories of drug, the depressant category is probably one of the most abused. Alcohol sits within this category as it is generally considered to be a depressant, however recent research has shown that alcohol, per se may cause a stimulant effect to certain areas of the brain – but that’s another issue.

Also in this category are the prescription drugs such as Diazepam, Temazepam (known as Benzodiazepines), Prozac, (Anti-depressant) Gamma Hydroxy Buterate (GHB, used in some cases of ‘date rape’ and in gymnasiums), and Haldol (Anti-psychotics).

It also includes the barbiturate drugs, which are very rarely used today in the medical profession and difficult to obtain on the black market. Many of the effects will be seen when a person takes an overdose either accidentally or deliberately. If a person keeps to their prescribed dose, these effects will not be seen. Effects seen during drunkenness are the general effects of the depressant category of drug. The use of depressant drugs and alcohol is a particularly disastrous combination and can have an unpredictable and lethal action. High doses of depressants will produce drunken like behaviour but without the smell of intoxicants.

Depressant category observations include:

  • Normal pupils
  • Watery eyes
  • Drowsy
  • Thick, slurred, slow speech
  • Uncoordinated
  • Dis-inhibition
  • Impaired judgement
  • Impaired vision
  • Wide emotional effects
  • Rancid odour on breath (Vomit)

The effects of these drugs vary widely. We know that alcohol will be eliminated from the body at a rate of 15% (1 Unit) per hour.

GHB is eliminated quickly between 4 – 8 hours and is generally undetectable in the blood or urine once the effects have worn off.

Prescription pharmaceuticals will always present themselves in the blood or urine simply because they are used as a maintenance dose and the effects of Barbiturates generally wane after about 16 hours.


Hallucinogenic drugs have been available for many decades. The most famous of these is of course LSD (Lysergic Acid Diethylamide). Following its decline in the 80’s and 90’s, the use of LSD is once again on the increase, particularly within the ‘rave’culture. Many users of LSD experience psychedelic hallucinations and may also experience a mixing of the senses. This is known medically as synaesthesia. Users may also suffer from nausea and a phenomenon known as ‘flashbacks’. These flashbacks may occur at any time, possibly years, after the person has stopped using the drug. Flashbacks are most common when a person experiences sights, sounds or smells reminiscent of their original experience. Many frequent users of LSD, particularly from the 60’s and 70’s may be affected by its use for the rest of their lives (‘acid casualties’). LSD is a drug that is transdermal, which means that it can be absorbed through the skin.

One of the most common hallucinogens is Ecstasy. Used and frequently abused at parties, raves and other social functions, ecstasy has become synonymous with the party culture. Some high profile deaths have attempted to show the dangers of ecstasy use, but that does not stop 400,000 ‘e’s being ‘popped’ at the weekend in the UK.

Ecstasy can be described as an ‘hallucinogenic stimulant’ or ‘psychedelic amphetamine’. It was originally developed as an aide to the sufferers of Parkinson’s disease, until the serious side effects were discovered. It has also been used as a therapeutic aide in assisting people with marital problems because of its empathic qualities and appeared in the 1960’s at beach parties on the west coast of America. Interestingly the use of Ecstasy in the US did not explode over the country the way it has done in Europe and the UK since the 1990’s.

The problems with Ecstasy have only recently been researched. Ecstasy is an emetic, which means that the body retains water and stops urination. As a result it stimulates the body’s metabolism so those users who exert themselves physically at parties and raves are unable to urinate to dispose of all the water they may drink to keep themselves hydrated, which has a devastating effect on the body and causes death. Conversely, if users fail to keep themselves hydrated then the opposite reaction, dehydration, and death from overheating will occur.

Generally the following may be observed when a person is under the influence:

  • Pupils (Normal – LSD/Dilated Ecstasy)
  • Dazed appearance
  • Uncoordinated
  • Poor balance
  • Distorted time & distance perception
  • Sweating
  • Goose bumps (piloerection
  • Paranoia
  • Nausea
  • Hallucinations
  • Synaesthesia
  • Flashbacks

Other drugs in this category are magic mushrooms (Psilocybin), some other psychedelic tryptamines, (5-Meo-DMT), Bufotinine (Venom from the Bufo Toad).


The use of inhalant type drugs was common among people in the late 80’s and early 90’s. This abuse amongst teenagers precipitated legal changes in the way that volatile solvents are sold. Of all the categories of drug this is the most dangerous causing the death of 1/5th (20%) of first time users.

Inhalant type drugs have a short duration, the onset of any effect will be almost immediate, but the post use effects may last up to two hours, if at all. Excessive use of inhalant type drugs affects cognitive behaviour and damages the cerebellum, causing learning difficulties.

The following may be observed;

  • Normal Pupils
  • Substance residue around the mouth
  • Substance odour
  • Nausea
  • Slurred speech
  • Disorientation/confusion
  • Drowsy
  • Watery/bloodshot eyes
  • Lack of muscle control
  • Flushed face
  • Non-communicative
  • Intense headache

Disassociative Anaesthetics

Dissociative anaesthetics (DA) are drugs, which, as they would suggest, disassociate the user from any pain. The most common DA is Phencyclidine or PCP. Known also as ‘angel dust’ it is widely used in the USA and a common analogue of PCP used in the UK is Ketamine, a vetinary tranquilliser.

Originally designed for use on the battlefields of Vietnam, it is a drug that allows surgery to be performed whilst the subject is awake! Similarly, if a person under the influence of a DA turns to violence, as most do, then it would be extremely difficult to control that person. It poses an extreme health and safety risk to both the user and other employees and person under the influence of such drugs must only be dealt with by the police.

These drugs produce impairment and other observable signs that are a combination of the Depressant, Stimulant and Hallucinogen drug categories.

Observations will include:

  • Normal pupils
  • Slow, slurred speech
  • Loss of memory
  • Agitation
  • Excitement
  • Cyclic behaviour
  • Smell of ether
  • Rigid muscle tone
  • Increased pain threshold
  • Extreme heat
  • Profuse sweating
  • Sensory distortions
  • Auditory hallucinations
  • Loss of personal identity
  • Passivity, but the subject may turn abruptly violent if confronted with a threatening situation
  • Blank Stare

© S G Collier.Taken from an original document May 2004. March 2015

Blue Knight Drugs and Alcohol TrainingDrug Recognition Techniques Under the Influence at WorkDrug and Alcohol ResourcesDrug DriveDrink Drive