In normal aging humans there is a progressive decrease of oxygen and glucose consumption with a reduction of cerebral blood flow (CBF), which could be responsible for age-related changes in cognitive functions. A baboon model under anaesthesia using single photon emission computed tomography (SPECT) of the brain and the radiopharmaceutical hexamethylpropylene amine oxime (99mTc-HMPAO) has been developed and found to be sensitive to the effects of drugs that are known to increase CBF. In the present study, the effect of two haemorrheologically active drugs, viz a combination of pentifylline (CAS 1028-33-7) and nicotinic acid (CAS 59-67-6) vs. piracetam (CAS 7491-74-9) were compared with the known effect of acetazolamide (CAS 59-66-5) on CBF in the baboon model using the 99mTc-HMPAO split dose method. Acetazolamide (p < 0.05) and the combination of pentifylline and nicotinic acid (p < 0.01) increased the CBF when compared with the control baseline. The CBF was not significantly increased upon treatment with piracetam, pentifylline alone and nicotinic acid alone, when compared with the control values for total brain ratios (p > 0.05). However, an increased regional effect was observed for piracetam. These results indicate that the above haemorrheologically active drugs exhibit specific but different effects on cerebral blood flow with possible clinical implications.