Understanding the medication
Over-the-counter (OTC) travel sickness tablets typically contain antihistamines like dimenhydrinate (e.g., Dramamine) or meclizine (e.g., Bonine), or an anticholinergic agent like hyoscine hydrobromide (e.g., Kwells). These active ingredients work by blocking the nerve signals that cause nausea and vomiting, but they can also affect other parts of the body. Taking more than the recommended dose increases the concentration of the drug in your system, which can amplify both the intended effects and the unwanted side effects.
Common active ingredients and their properties
- Dimenhydrinate: A sedating antihistamine that is converted into diphenhydramine in the body. It works by depressing the central nervous system to reduce motion sickness symptoms. It is known for causing significant drowsiness.
- Meclizine: A less-drowsy antihistamine compared to dimenhydrinate, meclizine blocks signals in the brain related to balance. It is a popular choice for those who need to remain alert.
- Hyoscine Hydrobromide: This anticholinergic agent works by blocking nerve signals from the inner ear to the vomiting center in the brain. It is considered one of the most effective treatments for motion sickness but is known to cause side effects such as dry mouth and blurred vision.
- Promethazine: A long-acting, highly sedating antihistamine effective for extended trips. Due to its strong sedative effects, a double dose could significantly increase drowsiness.
Immediate effects of a double dose
If you have taken an extra dose of a travel sickness tablet, the immediate effects will depend on the specific medication and your body's sensitivity. For many people, a single extra dose, particularly of a milder drug like meclizine, may only lead to intensified side effects. However, for a more potent or sedating medication like dimenhydrinate or promethazine, the consequences can be more pronounced.
Mild to moderate symptoms
- Increased drowsiness and fatigue: The most common effect of a double dose, especially with sedating antihistamines, is a significant increase in sleepiness. This can be dangerous if you need to drive or operate machinery.
- Blurred vision and dry mouth: These are typical anticholinergic side effects that become more noticeable at higher doses.
- Dizziness and loss of coordination: An increased dose can disrupt your sense of balance, leading to more intense dizziness and unsteadiness.
- Hyperactivity or excitement (especially in children): Paradoxically, some travel sickness medications can cause central nervous system stimulation in children, leading to agitation and excitability instead of sedation.
Severe symptoms and overdose risks
While a single extra tablet may not be an immediate danger for a healthy adult, taking multiple extra doses or combining medications can lead to a severe overdose. This is particularly risky for children and older adults. Severe overdose symptoms require immediate emergency medical attention.
Potential severe symptoms include:
- Cardiac issues: A fast or irregular heartbeat (tachycardia) is a significant risk with higher doses. Severe cases can involve dangerous heart arrhythmias.
- Hallucinations and confusion: High doses, especially of dimenhydrinate and hyoscine, can cause mental status changes, disorientation, and seeing or hearing things that aren't there.
- Seizures or convulsions: The central nervous system can be overstimulated by high doses of antihistamines, leading to seizures.
- Difficulty urinating: Anticholinergic effects can lead to urinary retention.
- Coma: In the most severe cases of overdose, a person may become unconscious.
Comparison of Double-Dosing Risks by Medication Type
| Feature | Dimenhydrinate (Dramamine) | Meclizine (Bonine) | Hyoscine (Kwells, Scopoderm) |
|---|---|---|---|
| Drug Class | Sedating antihistamine | Less-drowsy antihistamine | Anticholinergic |
| Risk of Increased Drowsiness | High | Low to Moderate | Moderate to High |
| Risk of Blurred Vision | Moderate | Low | High |
| Risk of Dry Mouth | Moderate | Low | High |
| Risk of Hallucinations | Moderate to High at very high doses | Very Low | High at higher doses |
| Risk of Cardiovascular Issues | Moderate to High at very high doses | Low | High at higher doses |
| Who is at higher risk for severe effects? | Infants, older adults | Children, older adults | Children, older adults |
| What to do for a double dose? | Contact Poison Control | Contact Poison Control | Contact Poison Control |
What to do if you take an extra tablet
If you have accidentally taken two travel sickness tablets, your immediate action is crucial for your safety and well-being. The proper response depends on the severity of the symptoms you are experiencing.
- Assess the situation: If you are a healthy adult and took one extra tablet a couple of hours early, you might just experience more drowsiness. Monitor yourself for any new or concerning symptoms.
- Contact a healthcare professional: For any dosing error, especially with potent medications or if you are unsure, it is always best to seek professional advice. You can call your pharmacy for guidance on what to watch for and what to expect.
- Call Poison Control: This is a valuable, free, and confidential resource available 24/7. Their experts can provide personalized guidance based on the medication, amount taken, and your age and weight. In the US, the number is 1-800-222-1222.
- Seek emergency medical help: If you or someone with you experiences any severe symptoms such as collapse, seizures, severe confusion, breathing difficulty, or a significantly fast or irregular heartbeat, call 911 or your local emergency number immediately.
Preventing future medication errors
To prevent accidentally taking an extra dose in the future, consider implementing these simple strategies:
- Use a pill organizer: A weekly or daily pillbox can help you visually track which doses you have already taken.
- Keep a medication log: For scheduled daily medications, a log can help prevent confusion, especially if multiple people are involved in giving the medication.
- Set an alarm: Setting a daily reminder on your phone can help ensure you take your medication at the correct time.
- Store medication properly: Always keep medications in their original, clearly labeled containers and out of reach of children.
Conclusion
Taking two travel sickness tablets can increase the intensity of common side effects, such as drowsiness, blurred vision, and dry mouth. While a single, mild dosing error may not be serious for a healthy adult, it's never advisable to exceed the recommended dosage. For potent anticholinergic medications like hyoscine or high doses of sedating antihistamines like dimenhydrinate, a double dose could lead to dangerous complications, including cardiac arrhythmias, hallucinations, and seizures. Always consult a healthcare provider or Poison Control after a dosing error, and seek immediate emergency care for severe symptoms. Prevention through careful tracking and proper storage is the best way to ensure medication safety. For further information on managing medication errors, refer to reliable resources like the Poison Control website.
