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, fen ma mei min (酚麻美敏), fufang an fen wan an (复方氨酚烷胺) and an ka huang min (氨咖黄敏), 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. State Food and Drug Administration (2010). Adverse Drug Reaction Information Bulletin (No. 32): attention to the safety of the Chinese-Western compound preparation Vitamin C Yinqiao Tablets [in Chinese]. https://www.nmpa.gov.cn/xxgk/yjjsh/ypblfytb/20100919162601498.html
2. National Medical Products Administration (2020). The public's top ten medication tips of 2020 | (3) Be careful with cold medicines; safe and rational use is the key [in Chinese]. 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. Road Traffic Safety Law of the People's Republic of China (2021 amendment), Article 22, paragraph 2 [in Chinese]. 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