Which of the following drugs crosses the blood-brain barrier

Diphenoxylate It is a synthetic opioid, chemically related to pethidine; used exclusively as constipating agent; action is similar to codeine. The antidiarrhoeal action is most prominent, but because it is absorbed systemically and crosses blood-brain barrier--CNS effects do occur. Atropine is added in subpharmacological dose to discourage abuse by taking several tablets. adverse effects:- respiratory depression, paralytic ileus and toxic megacolon in children. contraindication:- contraindicated below 6 years of age. Ref:- kd tripathi; pg num:-686