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Ketotifen (Zaditen) is a widely used prophylactic antiasthmatic drug with pronounced antianaphylactic properties and a specific H1-antihistaminic effect. This article summarises the available information on acute overdosage of this drug, which was reported in 13 adults and 8 children. The symptoms of acute overdosage observed with ketotifen are similar to those described for antihistaminic agents. However, it would appear that the acute toxicity of ketotifen is rather low, since no serious effects have been reported either in children or in adults after the intake of up to 20mg of ketotifen, which is 10 times the recommended dose. No lethal outcome of acute overdosage has been described in association with this drug. Ketotifen seems to be better tolerated in children than in adults. Based on present clinical experience, management of acute overdosage includes gastric lavage within 2 to 4h after ingestion or activated charcoal after this period. Symptomatic treatment is indicated if arrhythmias, hypotension or seizures develop, and the patient should be kept under surveillance for at least 6 to 8h.

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Reactive scattering of ground state O( 3 P) atoms with C 2 H 4 S and C 4 H 4 S molecules has been studied at an initial translational energy E ∼ 40 kJ mol -1 using a supersonic beam of O atoms seeded in He buffer gas generated from a microwave discharge source. The center-of-mass angular distribution of SO scattering for O + C 2 H 4 S is cone-shaped in the backward hemisphere at a scattering angle θ ∼ 120°with respect to the incident O atom direction, while the OC 4 H 3 S scattering for O + C 4 H 4 S is nominally isotropic. The O + C 2 H 4 S reaction disposes a lower fraction (f ′ ∼ 0.3) of the total available energy into product translation than the O + C 4 H 4 S reaction (f ′ ∼ 0.4), although the product translational energies are higher by a factor of ∼2 for the more exoergic O + C 2 H 4 S reaction. The O + C 2 H 4 S reaction involves cleavage of the three-membered ring of the thiirane molecule, while the O + C 4 H 4 S reaction involves H atom displacement from the fivemembered ring of the thiophene molecule. Both reactions occur on the triplet potential energy surface. The strongly exoergic concerted rupture of the three-membered thiirane ring disposes half the available energy into vibrational excitation of the ethene product molecule compared with only a fraction (∼0.13) being disposed into SO product vibration. The displacement reaction of the five-membered thiophene ring involves O atom addition forming a persistent OC 4 H 4 S complex with a potential energy barrier to H atom displacement.

Reactive scattering of O(3P) atoms with CH2ICl molecules has been measured at initial translational energies E ∼ 46 and 17 kJ mol-1 using a supersonic beam of O atoms seeded in He and Ne buffer gases generated from a high-pressure microwave discharge source. At the higher initial translational energy, the IO product scattering can be resolved into two components; one showing forward and backward peaking with a product translational energy distribution peaking at low energy with a tail extending out to higher energy, and the other that peaks in the backward direction with higher product translational energy. At lower initial translational energy, the IO product scattering does not allow the resolution of two components but peaks in the backward direction with a higher product translational energy than for scattering in the forward hemisphere. The slow component is attributed to dissociation of a long-lived OICH2Cl complex formed by intersystem crossing from the initial triplet 3A‘‘ potential energy surface to the underlying singlet 1A‘ potential energy surface. The fast component is attributed to direct reaction over the triplet potential energy surface with the sharp backward peaking arising from reaction on the 3Π2 and 3Π1 spin multiplet surfaces in near collinear OICH2Cl configurations and the scattering in the sideways and forward directions arising from reaction on the 3A‘‘ Renner Teller surface in strongly bent configurations. The contribution of the slow component is approximately one-third that of the fast component to the total reaction cross section for IO product scattering.