Barbiturates: Physiological effects

Last modified: Thursday, 25. December 2008 - 6:11 am


Barbiturates act on the central nervous system, and use of these drugs can bring about changes ranging from mild sedation to a coma. Furthermore, an overdose or an attempt to withdraw abruptly from barbiturates can be fatal.

Short-term effects

Barbiturates help a person to sleep. However, this slumber differs from normal sleep. Barbiturate use decreases the amount of the dream phase of sleep known as the rapid eye movement (REM) stage. This phase of sleep is necessary for maintaining good health.

Barbiturates produce reactions similar to those of alcohol. A person may experience “hangover” symptoms including headache and dizziness. They may still feel tired and less alert as well. A person experiencing these symptoms should not drive or operate machinery. These hangover symptoms may last for hours.

Like alcohol, barbiturates are intoxicating. During the stage after mild intoxication, the person’s speech may be slurred. The person may stagger and lose muscular control. Other symptoms of intoxication include irritability, shallow breathing, and fatigue.

At-risk groups

Older adults and pregnant women should consider the risks associated with barbiturate use. When a person ages, the metabolization rate for drugs decreases. As a result, people over age 65 are at higher risk of the harmful effects of barbiturates. There is also greater risk for drug dependence.

When barbiturates are taken during pregnancy, the drug passes through the mother’s bloodstream and through the placenta into the fetus. After the baby is born, it may experience withdrawal symptoms and have trouble breathing. Other withdrawal symptoms include troubled sleep patterns, fever, and irritability. Furthermore, nursing mothers who take barbiturates may transmit the drug in their breast milk.

Harmful side effects

An individual using CNS depressants like barbiturates can develop a tolerance for the drugs. Over time, the body becomes used to the presence of barbiturates in the system. When this happens, the prescribed dose of the drug does not produce a desired result and the individual may take more pills or stronger dosages of barbiturates. A tolerance to that level can develop, requiring even more barbiturates or a stronger dosage. As tolerance continues to increase, the individual may take a fatal dose in their attempt to get the desired effect.

Overdose occurs when a drug is consumed in a dose that is greater than the body can handle. Symptoms of an overdose include intense tiredness, confusion, irritability, and fever or a low body temperature. The person may experience shortness of breath, sleepiness or difficulty getting to sleep, and weakness. Other signs of overdose are slurred speech, a slow heartbeat, and uncommon eye movements.

An overdose may be triggered by drinking alcohol or taking a drug like an amphetamine while using barbiturates. In an effect called synergy, the two drugs intensify the effects of each other. As a result, the prescribed dose of one drug could be fatal if taken with another drug.

The amount of a fatal dosage of barbiturate will vary with the individual. However, the lethal dose is usually 10 to 15 times as large as a usual dose. A fatal overdose starts with cardiovascular collapse followed by respiratory depression. The person then falls into a coma and dies.

Long-term health effects

Barbiturates are addictive. A person may develop a physical dependency after taking more than 400 mg of pentobarbital or secobarbital a day over an approximately 90-day period.

Long-term use of other barbiturates can also lead to physical and psychological dependence. Symptoms of dependence include the feeling that a person cannot relax or sleep without taking a barbiturate. Another sign of addiction is a tendency to increase the dosage.

People at risk of barbiturate abuse and addiction include alcoholics and abusers of opiates, sedative-hypnotics, and amphetamines.


When a person stops taking barbiturates, the body begins to adapt to the lack of drugs in the system. If a person has used barbiturates in large doses or for an extended period of time, a physician should be consulted about the withdrawal process.

Onset of withdrawal symptoms usually begin eight to 16 hours after the last pill was taken. Symptoms may last up to 15 days if the person was a long-term barbiturate user or took large doses of the drug.

During this time, the person feels weak, dizzy, and anxious. Withdrawal brings tremors and shakes. The person may hallucinate, experience delusions, or become violent and hostile. Withdrawal symptoms generally diminish over time.

In some cases, withdrawal symptoms can be fatal, so a person cannot just stop taking barbiturates. The physician will establish a plan of gradual withdrawal from barbiturates.


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