Penicillins are prone to cause allergic reactions features like rash on skin, hypotension ,difficulty in breathing are suggestive of anaphylactic shock. Drugs Frequently causing allergic reactions Penicillins Aspirin Cephalosporins Indomethacin Sulfonamides Carbamazepine Tetracyclines Allopurinol Quinolones ACE inhibitors Metronidazole Methyldopa Abacavir Hydralazine Antitubercular drugs Local anaesthetics Phenothiazines In case of anaphylactic shock the resuscitation council of UK has recommended the following measure : * Put the patient in reclining position, administer oxygen at high flow rate and perform cardiopulmonary resuscitation if required.* Inject adrenaline 0.5 mg (0.5 ml of I in I 000 solution for adult, 0.3 ml for child 6-12 years and 0.15 ml for child upto 6 years) i.m.; repeat every 5-10 min in case patient does not improve or improvement is transient. This is the only life saving measure. Adrenaline should not be injected i.v. (can itself be fatal) unless shock is immediately life threatening. If adrenaline is to be injected i. v., it should be diluted to 1:10,000 or 1:100,000 and infused slowly with constant monitoring. * Administer a H1 antihistaminic (pheniramine 20-40 mg or chlorpheniramine I 0-20 mg) i.m./slow i.v. It may have adjuvant value.* Intravenous glucocoicoid (hydrocoisone sod. succinate 200 mg) should be added in severe/recurrent cases. It acts slowly, but is specially valuable for prolonged reactions and in asthmatics. It may be followed by oral prednisolone for 3 days.