Cyclizine is a medication that helps prevent and treat nausea, vomiting, and dizziness, commonly associated with motion sickness, vertigo, and post-operative recovery. As an antihistamine with anticholinergic properties, it works by blocking signals to the brain that cause feelings of sickness. While effective for its intended purpose, its anticholinergic action means it is not suitable for everyone and requires caution in specific patient populations. A thorough review of a person's medical history and current medications is essential before beginning cyclizine treatment.
Serious Health Conditions Where Cyclizine Is Contraindicated
For certain health issues, the use of cyclizine is strictly advised against due to its pharmacological effects exacerbating the underlying condition. Ignoring these contraindications can lead to serious health risks.
Glaucoma
Cyclizine has anticholinergic effects that can increase intraocular pressure, which is a major risk factor for worsening glaucoma, particularly angle-closure glaucoma. Patients with this eye condition should not take cyclizine.
Prostate Enlargement and Urinary Retention
Men with an enlarged prostate (benign prostatic hyperplasia) or those who experience difficulty urinating should avoid cyclizine. The medication's anticholinergic properties can make urination even more difficult and potentially lead to acute urinary retention.
Respiratory Conditions
Patients suffering from respiratory illnesses such as asthma, bronchitis, or chronic obstructive pulmonary disease (COPD) should use cyclizine with caution. The anticholinergic effects can lead to a thickening of bronchial secretions, potentially obstructing the respiratory tract.
Obstructive Gastrointestinal Disorders
Cyclizine should not be used in individuals with conditions that can lead to bowel obstruction, such as Crohn's disease, diverticulitis, hernias, or colon cancer. The anticholinergic effect slows down the gastrointestinal tract, which can worsen an obstruction.
Severe Heart Conditions
Extreme caution is advised for patients with severe heart failure or a recent myocardial infarction. In some cases, cyclizine can cause a fall in cardiac output alongside increases in heart rate and arterial pressure. Serious cardiac symptoms, including fast or irregular heartbeats, can also occur.
Rare Blood Disorder (Porphyria)
Cyclizine should be avoided by individuals with a rare inherited blood disorder called porphyria.
Severe Liver Disease
Individuals with severe liver disease should use cyclizine with caution. Liver problems can exacerbate the medication's sedative effects.
Key Drug Interactions to Avoid
Combining cyclizine with certain substances or other medications can increase the risk of adverse side effects, including severe central nervous system (CNS) depression, drowsiness, and impaired coordination.
- Alcohol: This is a particularly dangerous combination. Both cyclizine and alcohol are CNS depressants, and taking them together significantly enhances their sedative effects. This can lead to excessive drowsiness, impaired breathing, and difficulty waking up.
- Other CNS Depressants: This includes prescription medications like tranquilizers, sedatives, sleeping pills, and opioid pain medicines. Combining them with cyclizine can worsen sedative effects and increase the risk of respiratory depression.
- Anticholinergic Drugs: Because cyclizine already has anticholinergic properties, combining it with other drugs that share this effect (e.g., some antidepressants) can heighten side effects like dry mouth, constipation, and blurred vision.
- Monoamine Oxidase Inhibitors (MAOIs): Taking cyclizine with MAOI antidepressants is not recommended as it can affect how cyclizine works and increase the chance of side effects.
- Ototoxic Drugs: Cyclizine can mask the early warning signs of damage to the inner ear caused by ototoxic drugs, such as certain aminoglycoside antibiotics.
Specific Patient Populations Requiring Caution
Pregnant and Breastfeeding Individuals
While cyclizine has an FDA pregnancy category B rating, meaning it is not expected to harm an unborn baby, it is generally advised to avoid its use during pregnancy unless absolutely necessary. Regarding breastfeeding, cyclizine is excreted in human milk, and while occasional doses might be acceptable, prolonged use or high doses may cause effects in the infant or decrease milk supply.
The Elderly
Elderly patients are often more sensitive to the anticholinergic effects of cyclizine, making them more prone to side effects such as confusion, dizziness, dry mouth, and urinary retention. Dose adjustments and close monitoring are typically required.
Children
Cyclizine is not recommended for children under 6 years of age. In older children, a smaller, age-appropriate dose is used, as they can be more susceptible to side effects.
Important Situations to Consider
- Driving and Operating Machinery: Cyclizine can cause drowsiness, blurred vision, and affect coordination, especially when first starting the medication. Patients should not drive or operate heavy machinery until they know how it affects them.
- Before an Allergy Test: The antihistamine action of cyclizine can affect the results of allergy skin tests. You may need to stop taking it a few days beforehand.
- Misuse and Overdose Risk: Cyclizine has a potential for abuse due to its euphoric or hallucinatory effects when taken in high doses. Overdoses are particularly dangerous and can cause extreme drowsiness, hallucinations, rapid heartbeat, and seizures.
Comparing Cyclizine with Alternative Medications
When cyclizine is not suitable due to contraindications, several alternative medications may be considered depending on the underlying cause of nausea. Below is a comparison of cyclizine and some common alternatives.
| Feature | Cyclizine (Antihistamine) | Metoclopramide (Prokinetic) | Ondansetron (Serotonin Blocker) |
|---|---|---|---|
| Mechanism | Blocks histamine receptors and has anticholinergic effects. | Increases stomach muscle contractions. | Blocks serotonin receptors in the gut and brain. |
| Good for | Motion sickness, vertigo, post-op nausea. | Gastric stasis, post-op nausea. | Chemo-induced nausea, severe vomiting. |
| Common Side Effects | Drowsiness, dry mouth, constipation. | Fatigue, restlessness, anxiety. | Headache, constipation. |
| Glaucoma Risk | High (Anticholinergic effect increases eye pressure). | Low (Not anticholinergic) | Low (Not anticholinergic) |
| Prostate Enlargement Risk | High (Anticholinergic effect can cause urinary retention). | Low (Not anticholinergic) | Low (Not anticholinergic) |
| CNS Depression Risk | High (With alcohol or other depressants). | Moderate | Low |
| Pregnancy Safety | Category B, caution advised. | Considered safer, but always consult a doctor. | Often used, considered safe in later trimesters. |
Conclusion
While cyclizine is an effective and common treatment for several forms of nausea, it is not a suitable option for everyone. Before taking it, you must be aware of its contraindications, including conditions like glaucoma, prostate enlargement, and certain respiratory or heart problems. It is also critical to understand its interactions with other medications and substances, especially alcohol and other CNS depressants. Specific patient populations, such as the elderly, children under 6, and pregnant or breastfeeding individuals, require additional caution. Always consult a healthcare professional to ensure that cyclizine is safe for your specific situation and to discuss alternative treatments if necessary. For more information, you can also consult resources like the official NHS guidance on cyclizine.
