Respa SA Side Effects
Generic name: diphenhydramine / pseudoephedrine
Medically reviewed by Drugs.com. Last updated on Oct 11, 2022.
Note: This document contains side effect information about diphenhydramine / pseudoephedrine. Some dosage forms listed on this page may not apply to the brand name Respa SA.
Applies to diphenhydramine / pseudoephedrine: oral liquid, oral tablet, oral tablet disintegrating.
Central nervous system (CNS) depression commonly occurs with diphenhydramine administration, resulting in drowsiness and sedation in nearly all patients treated. Motor skills may be impaired. Dystonic reactions have been reported after single doses of diphenhydramine.
Pseudoephedrine produces nervous system stimulation, resulting in tremor, anxiety, and nervousness. Insomnia is reported in up to 30% of pseudoephedrine-treated patients. Headache may also occur in patients receiving pseudoephedrine.[Ref]
The CNS depressant effect of diphenhydramine parallels its plasma concentrations. The plasma concentration threshold for sedation is 30 to 42 ng/mL, and to cause mental impairment is 58 to 74 ng/mL. Patients should be warned against driving while taking diphenhydramine, and should avoid concomitant ingestion of alcohol.
Dystonic reactions to diphenhydramine have been accompanied by dizziness, mental confusion, rigidity, lip and tongue protrusion, trismus, torticollis, and swallowing difficulties. These reactions generally resolve spontaneously. Toxic encephalopathy has been reported in a child with chicken pox treated generously with topical diphenhydramine.
Pseudoephedrine causes vasoconstriction which generally does not produce hypertension, but may be problematic for patients with pre-existing hypertension. Arrhythmias may be produced in predisposed patients. Rarely, pseudoephedrine has been reported to cause coronary artery spasm and chest pain.[Ref]
Cardiovascular adverse effects more commonly may be associated with pseudoephedrine. Pseudoephedrine generally causes a significant rise in heart rate. Hypertension and arrhythmias may be problematic in susceptible patients.[Ref]
Hypersensitivity reactions to pseudoephedrine may also occur. Fixed drug eruptions secondary to pseudoephedrine have been reported.[Ref]
Most commonly, hypersensitivity to diphenhydramine manifests itself in patients receiving systemic drug after being sensitized to it by topical application. Sensitization with systemic administration has also been reported.[Ref]
Ocular affects of diphenhydramine may include blurred vision, diplopia, and dry eyes due to its anticholinergic effect.[Ref]
More about Respa SA (diphenhydramine / pseudoephedrine)
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1. Lavenstein BL, Cantor FK "Acute dystonia: an unusual reaction to diphenhydramine." JAMA 236 (1976): 291
2. Carruthers SG, Shoeman DW, Hignite CE, Azarnoff DL "Correlation between plasma diphenhydramine level and sedative and antihistamine effects." Clin Pharmacol Ther 23 (1978): 375-82
3. Gengo F, Gabos C, Miller JK "The pharmacodynamics of diphenhydramine-induced drowsiness and changes in mental performance." Clin Pharmacol Ther 45 (1989): 15-21
4. Burns M, Moskowitz H "Effects of diphenhydramine and alcohol on skills performance." Eur J Clin Pharmacol 17 (1980): 259-66
5. Roila F, Donati D, Basurto C, Del Favero A "Diphenhydramine and acute dystonia ." Ann Intern Med 111 (1989): 92-3
6. Davenport PM, Wilhelm RE "An unusual vasculitis due to diphenhydramine. Cutaneous and central nervous system involvement." Arch Dermatol 92 (1965): 577-80
7. Filloux F "Toxic encephalopathy caused by topically applied diphenhydramine." J Pediatr 108 (1986): 1018-20
8. Brait KA, Zagerman AJ "Dyskinesias after antihistamine use ." N Engl J Med 296 (1977): 111
9. Jones B, Lal S "Tardive dyskinesia uncovered after ingestion of Sominex, an over-the- counter drug." Can J Psychiatry 30 (1985): 370-1
10. Santora J, Rozek S, Samie MR "Diphenhydramine-induced dystonia ." Clin Pharm 8 (1989): 471
11. Borbely AA, Youmbi-Balderer G "Effect of diphenhydramine on subjective sleep parameters and on motor activity during bedtime." Int J Clin Pharmacol Ther Toxicol 26 (1988): 392-6
12. Stroh JE, Jr Ayars GH, Bernstein IL, Kemp JP, Podleski WK, Prenner BM, Schoenwetter WF, Salzmann JK "A comparative tolerance study of terfenadine-pseudoephedrine combination tablets and pseudoephedrine tablets in patients with allergic or vasomotor rhinitis." J Int Med Res 16 (1988): 420-7
13. Loizou LA, Hamilton JG, Tsementzis SA "Intracranial haemorrhage in association with pseudoephedrine overdose." J Neurol Neurosurg Psychiatry 45 (1982): 471-2
14. Dickerson J, Perrier D, Mayersohn M, Bressler R "Dose tolerance and pharmacokinetic studies of L (+) pseudoephedrine capsules in man." Eur J Clin Pharmacol 14 (1978): 253-9
15. Covington TR, eds., Lawson LC, Young LL "Handbook of Nonprescription Drugs." Washington, DC: American Pharmaceutical Association (1993):
16. Tejera CA, Saravay SM, Goldman E, Gluck L "Diphenhydramine-induced delirium in elderly hospitalized patients with mild dementia." Psychosomatics 35 (1994): 399-402
17. Mariani PJ "Pseudoephedrine-induced hypertensive emergency: treatment with labetalol." Am J Emerg Med 4 (1986): 141-2
18. Rosen RA "Angina associated with pseudoephedrine ." Ann Emerg Med 10 (1981): 230-1
19. Wiener I, Tilkian AG, Palazzolo M "Coronary artery spasm and myocardial infarction in a patient with normal coronary arteries: temporal relationship to pseudoephedrine ingestion." Cathet Cardiovasc Diagn 20 (1990): 51-3
20. Gordon RD, Ballantine DM, Bachmann AW "Effects of repeated doses of pseudoephedrine on blood pressure and plasma catecholamines in normal subjects and in patients with phaeochromocytoma." Clin Exp Pharmacol Physiol 19 (1992): 287-90
21. Horio T "Allergic and photoallergic dermatitis from diphenhydramine." Arch Dermatol 112 (1976): 1124-6
22. Emmett EA "Diphenhydramine photoallergy." Arch Dermatol 110 (1974): 249-52
23. Coskey RJ "Contact dermatitis caused by diphenhydramine hydrochloride." J Am Acad Dermatol 8 (1983): 204-6
24. Lawrence CM, Byrne JP "Eczematous eruption from oral diphenhydramine." Contact Dermatitis 7 (1981): 276-7
25. Shelley WB, Shelley ED "Nonpigmenting fixed drug eruption as a distinctive reaction pattern: examples caused by sensitivity to pseudoephedrine hydrochloride and tetrahydrozoline." J Am Acad Dermatol 17 (1987): 403-7
26. Tomb RR, Lepoittevin JP, Espinassouze F, Heid E, Foussereau J "Systemic contact dermatitis from pseudoephedrine." Contact Dermatitis 24 (1991): 86-8
27. Camisa C "Fixed drug eruption due to pseudoephedrine." Cutis 41 (1988): 339-40
28. Schuller DE, Turkewitz D "Adverse effects of antihistamines." Postgrad Med 79 (1986): 75-86
29. Seedor JA, Lamberts D, Bergmann RB, Perry HD "Filamentary keratitis associated with diphenhydramine hydrochloride (Benadryl)." Am J Ophthalmol 101 (1986): 376-7
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