The effects of a beta 2-agonist (clenbuterol), and anti-bacterial drugs (trimethoprim with sulphadiazine; oxytetracycline) on calf mucociliary clearance.

A non-invasive radio-aerosol technique was employed to study mucociliary clearance patterns in three groups of four calves of different ages. The initial clearance pattern, the percentage cleared in 1 h, and the percentage cleared between 1 and 19 h were used as indices of clearance efficiency. (Percentage retention at 19 h was used as an index of alveolar deposition.) These measurements were recorded in a series of experiments designed to investigate the effects of: clenbuterol (given as a single intravenous injection, 0.75 microgram/kg); a combination of trimethoprim and sulphadiazine-TMPS (administered by intramuscular injection twice daily for 3 days: 2.5 mg/kg trimethoprim; 12.5 mg/kg sulphadiazine) alone, or with a supplementary injection of clenbuterol; and oxytetracycline (administered by intramuscular injection twice daily for 3 days; 3 mg/kg). Clenbuterol alone tended to increase clearance rate, although this effect did not achieve statistical significance. The combination of TMPS with clenbuterol produced results similar to those of clenbuterol alone. Neither TMPS nor oxytetracycline had any significant effect on indices of mucociliary clearance. Differences were observed between calves of different age groups, particularly in clearance phases between 1 and 19 h.