I am Dr. Arun and will be helping you today.
I am sorry that your question was unanswered for long.
The common cause of passing out during a coughing bout is lack of blood supply to the brain. But there can be concomitant causes too as following;
1) bradyarrhythmias; this is sudden slowing of the heart. it is mainly due to sinus and atrial node dysfunctions. Sick sinus syndrome is a prototype of these arrhythmias and is a major cause for syncope. 24 hour Holter monitoring, echocardiography etc are the investigations done for it.
2) neurocardiogenic mechanisms; this is fall of the blood pressure suddenly due to a sudden sympathetic failure (failure of the autonomic nervous system).
3) carotid hypersensitivity syndrome is an exaggerated response to carotid sinus stimulation.
4) orthostatic hypotension is due to failure of autonomic nervous system and related heart regulatory mechanisms.
Having said that; cough need to be treated and most likely cause is post nasal drip with your description. It is also called as Chronic Upper Airway Cough Syndrome Secondary to Rhinosinus (nose and sinus) Diseases (Postnasal Drip Syndrome). The pathogenesis of this cough is mechanical stimulation of the cough reflex in the upper airway.
The treatment is;
1) nasal saline spray; do not need prescription for it.
2) nasal corticosteroids / nasal cromolyn / nasal antihistamines may also be needed,
3) oral leukotriene inhibitors and
4) oral antihistamines; you may try Claritin D which is over the counter.
Treating the cause of cough should be able to get rid of the passing out issue.
Please feel free for your follow up questions.
I would be happy to assist you further, if you need any more information.
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