If you have taken a cold medicine or allergy medicine that contains chlorpheniramine (扑尔敏) or diphenhydramine, don't drive, work at heights or operate machines while taking it

Cost

Free. Look at the ingredient list when you buy medicine. For the days you take it, travel by bus or taxi, or ask a doctor or pharmacist to switch you to one that doesn't cause drowsiness.

What you get

A 2010 adverse drug reaction bulletin from the National Medical Products Administration said that Vitamin C Yinqiao Tablets (维C银翘片) contain chlorpheniramine maleate, also called 扑尔敏. Its adverse reactions are mainly drowsiness, a feeling of weakness, sleepiness and dry mouth. The bulletin advised doctors and drugstores to remind patients: during the course of the medicine, do not drive machines, vehicles or boats, and do not do high-altitude work, machine operation or operate precision instruments. The administration's 2020 public medication reminder says combination cold medicines mostly contain allergy ingredients such as chlorpheniramine and diphenhydramine, which cause drowsiness. People who drive, operate machinery or work at heights should use them with caution. A U.S. driving-simulator trial enlisted 40 drivers with seasonal allergic rhinitis, aged 25 to 44. Each person, a week apart, had a different condition and drove for 1 hour each: diphenhydramine 50 mg, fexofenadine 60 mg, alcohol to a blood alcohol concentration of about 0.1%, and placebo. Fexofenadine is an allergy drug that doesn't cause drowsiness. In the ability to keep up with the speed of the car ahead, it was worst after diphenhydramine, while after alcohol and after fexofenadine it was clearly better. In the ability to stay in lane, it got worse after both alcohol and diphenhydramine. When the car ahead suddenly blocked the road, reaction was slowest after alcohol, an average of 2.21 seconds, and was 1.95 seconds after fexofenadine. Driving after fexofenadine was about the same as after placebo. The authors concluded that diphenhydramine affects driving more than alcohol does. The drivers' own reports of drowsiness did not show how well they drove, so you can't rely on “am I sleepy” to decide whether you can drive.

Notes

The combination cold medicines the administration named, 酚麻美敏 (fen ma mei min), 复方氨酚烷胺 (fufang an fen wan an) and 氨咖黄敏 (an ka huang min), all contain chlorpheniramine, so check the ingredient list before buying. What the Road Traffic Safety Law (道路交通安全法) expressly forbids is driving after taking state-controlled psychotropic or narcotic drugs. Ordinary cold medicines and allergy medicines are not among them; the ban on driving is written in package inserts and the administration's reminders. If you must take it and must drive, ask a doctor or pharmacist to switch to one that doesn't cause drowsiness. Many of these cold medicines also contain acetaminophen; see §34.1 (acetaminophen). For other risks of drowsy driving, see §1.9 (stop and rest when you're sleepy). Graded B because there is only one 40-person simulator trial and no real-road accident figures. The benefit is rated “small”: the endpoint is driving performance in a simulator, not accidents or deaths. The beneficiaries are, besides you, the family members in the car and other people on the road.

Evidence grade

B : Supported by research but without a precise number, or based on small or single studies.

Sources

1. 国家食品药品监督管理局 (2010). 药品不良反应信息通报（第32期）关注中西药复方制剂维C银翘片的安全性问题. https://www.nmpa.gov.cn/xxgk/yjjsh/ypblfytb/20100919162601498.html
2. 国家药品监督管理局 (2020). 2020年公众十大用药提示丨（三）感冒用药须谨慎，安全合理是关键. https://www.nmpa.gov.cn/xxgk/kpzhsh/kpzhshyp/20201111095256170.html
3. Weiler JM, Bloomfield JR, Woodworth GG, et al. (2000). Effects of fexofenadine, diphenhydramine, and alcohol on driving performance. A randomized, placebo-controlled trial in the Iowa driving simulator. Annals of Internal Medicine, 132(5):354-363. https://doi.org/10.7326/0003-4819-132-5-200003070-00004
4. 中华人民共和国道路交通安全法（2021 年修正）第二十二条第二款. https://flk.npc.gov.cn/detail?id=ff8081817ab231eb017abd617ef70519

Translated from the Chinese original. Original book, section 34, tip 12. This section is about health and medicines. It is general information, not a substitute for a doctor’s diagnosis or prescription. Content may be out of date and rules differ by place. When you actually deal with an agency, a doctor or a court, follow what local officials, doctors and lawyers tell you. Disclaimer