How Long Does Promethazine Stay in Your System? (Urine Detection, Drug Tests, Side Effects, and Recovery)

What Is Promethazine?

Promethazine is a prescription medication commonly used to treat conditions such as allergy symptoms, nausea and vomiting, motion sickness, and short-term sedation. It is classified as a sedating antihistamine [1], or first-generation antihistamine, because it blocks the effect of histamine on the body’s histamine H1 receptors and has a CNS depressant effect. This means that it acts to reduce the symptoms [2] of many allergic reactions but also has an effect on the brain and spinal cord—the central nervous system—by making the user sleepy or drowsy and reducing the feeling of nausea and vomiting.

Typically, it would be used prior to preparing for surgery, and/or to reduce the severity of nausea/vomiting associated with motion sickness or the effects of a chemotherapy drug. Promethazine has multiple brand names; Phenergan® is one of the most common. Promethazine may be taken orally in tablet or liquid form, or it may be administered by injection in a hospital or clinic setting. Although promethazine is effective when used according to a doctor’s instructions[3], it may cause drowsiness and has other side effects; therefore, knowing how long promethazine remains in a person’s body is particularly important to users.

How Promethazine Works in the Body

Promethazine blocks the action of histamine on the body’s H1 receptors and suppresses activity in the central nervous system (CNS), providing both sedation and reducing nausea. After ingestion, it undergoes first-pass metabolism [4] in the liver, which means the liver metabolizes the drug prior to reaching the rest of the body in its fully active form.

Promethazine is very protein-bound, which can influence how long it remains in the body and/or how long it remains active within the user’s body. According to pharmacological studies, the liver enzymes [2] are primarily responsible for the breakdown of promethazine before it is eliminated from the body via the urinary system.

How Long Does Promethazine Stay in Your Body?

Understanding Half-Life and Elimination

To determine how long a drug lasts, we first consider its half-life. A drug’s half-life refers to how long it takes an active drug in a person’s body to decrease by half. Based on studies of the average half-life for promethazine, it has an average half-life of 10-19 hours [3].

Since most medications will be cleared from the body after approximately 5 half-lives (meaning 90-95% of it has been cleared from your body), it is likely that promethazine will be present in your body for an average of 2-4 days after you stop taking it. This will depend greatly on the user’s individual circumstances.

Factors That Influence Clearance

The rate at which promethazine is metabolized and eliminated from a person’s body is influenced by many factors.

The most important factor affecting the rate of elimination of this drug is an individual’s overall metabolic rate, especially when the individual also has a metabolic condition such as obesity. An individual with an increased metabolic rate typically clears promethazine faster than someone with a lower metabolic rate.

In contrast, repeated and/or high-dosage use of promethazine generally results in longer detection times for the drug in the urine and/or blood of the user.

Age has an effect on the rate at which a person metabolizes promethazine. It is generally accepted that adults aged 65 [3] or older tend to metabolize medications more slowly than those who are younger.

Liver and/or kidney disease has an effect on how quickly a person metabolizes and eliminates drugs from their body. For example, a person who has liver or kidney disease [5] will be more susceptible to delayed elimination of promethazine.

There are also many other variables which can influence the elimination of drugs from the body. For instance, an individual’s environment (particularly the temperature and humidity), their level of hydration, and other drugs that the individual may be using concurrently with promethazine can all have an effect on the elimination time of promethazine.

In summary, any drug interaction(s) between promethazine and any other medications (e.g., opioids, alcohol, and/or other sedatives) can increase a person’s risk [1] for experiencing adverse effect(s) as a result of the synergistic effects of these medications, including depression in respiratory function (shallow breathing caused by the use of sedative medications) which can lead to lower levels of oxygen in the body.

Detection Times by Test Type

Although the clinical effects of promethazine typically last for 12 hours or less (including sedation and relief of symptoms), the length of time for which it can be detected in the body is significantly longer. This is why someone may appear to be unaffected but still have detectable amounts of promethazine in their body.

Promethazine and Drug Tests

While routine employment or probationary drug testing does not include testing for promethazine, specialty laboratories may test for it if the rationale is due to screening for either antihistamines or sedatives. False positives for promethazine are rare, however, if you undergo testing, you should:

• Inform the laboratory personnel of your prescription.
• Provide verification of your prescription from your doctor.
• Being forthright regarding medications reduces the likelihood of misinterpretation of results obtained from drug testing.

Risks, Side Effects, and Signs of Misuse

Promethazine can cause several side effects even when taken as directed, including drowsiness and dizziness [1], dry mouth and blurred vision, and malaise, which is a vague feeling of discomfort or fatigue.

Call your healthcare provider if you experience serious symptoms such as irrational thoughts, confusion [3], or severe emotional states like agitation, abnormal heartbeat or palpitations, or respiratory distress, a serious condition where the body struggles to get enough oxygen.

Promethazine Misuse and Substance Use Considerations

There has been an increase in the abuse of promethazine, particularly when used in combination with codeine to create a recreational mixture known as “lean.” In addition to tolerance, abuse or misuse of promethazine increases the longevity of the drug within the individual’s system, resulting in a greater opportunity for dependency.

Examples of misuse are consuming excessive dosages of promethazine, self-administering promethazine without physician direction, and/or suffering from blackouts (complete memory loss of actions while under the influence of the substance).

Recovery and Support

To successfully support individuals who are misusing substances and/or experiencing a dual diagnosis (a combination of a mental health diagnosis in addition to an addiction), we offer compassionate and supportive services that will help enhance a client’s ability to successfully recover from their addiction(s) and other mental health-related issues.