Salbutamol may cause fine tremor of skeletal muscle (particularly the hands), palpitations, tachycardia, nervous tension, headaches, peripheral vasodilation and rarely, muscle cramps to some patients. Very rarely, hypersensitivity reactions such as bronchospasm, urticaria, angioedema, hypotension and collapse have been reported with salbutamol. Side effects such as gastrointestinal discomfort, nausea and vomiting have occasionally been reported with guaifenesin, particularly in very large doses.