Drowsiness is often desirable effect in patients with dermatitis and pruritus, since it tends to decrease the level of perception and may also decrease emotional tension caused by the disease. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist. Can give him benadryl also?knicname on My son takes zyrtec and has rash on his legs, after being out in the weeds. Theoretically, serotonergic agents may also antagonize the pharmacologic effects of cyproheptadine and methysergide, although this effect has not been reported. Be cautious about taking Periactin if you have bronchial asthma, the eye condition called glaucoma, an overactive thyroid gland, high blood pressure, heart disease, or circulatory problems. Geriatric Use Clinical studies of Cyproheptadine HCl Tablets did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from periactin cash on delivery younger subjects.