We quantitated atropine plasma levels and monitored blood pressure, heart rate, and salivary secretion after ocular application. Eight patients received 40 microliters 1% atropine in the lower cul-de-sac of one eye in connection with ocular surgery. Atropine plasma levels were determined for 90 minutes by radioreceptor assay. The peak plasma atropine concentration of 860 +/- 402 pg/ml was reached within 8 minutes in all patients. The ocular absorption of atropine was at least as rapid as that reported for intramuscular administration. Ocular atropine did not affect patients' blood pressure or heart rate when compared with those of the placebo group. Thirty minutes after administration of atropine eyedrops, the salivary secretion in the experimental group was reduced, but was statistically insignificant from the placebo group.
The systemic absorption of scopolamine 0.25 % eyedrops given unilaterally was quantitated in eight patients following therapeutic drug application. Another set of eight patients received placebo drops to study the effect of scopolamine on heart rate, blood pressure and salivation. Scopolamine was rapidly and efficiently absorbed after its ocular administration. The peak plasma scopolamine concentration of 550±60 pg/ml was reached within 15 minutes in all but two patients. Ocular scopolamine did not affect patients blood pressure or heart rate when compared to patients in the placebo group. Thirty minutes after administration of scopolamine the salivary secretion was slightly but insignificantly reduced.
Ocular effects and plasma concentrations of cyclopentolate were studied in 8 volunteers after eyedrop application with two methods. While recumbent two 30 microliters drops of 1% cyclopentolate hydrochloride were instilled in randomized order either conventionally to the lower conjunctival cul-de-sac or on the inner canthus with eyes closed, followed by immediate opening of the eyes. The cycloplegic responses as well as the extent and time of maximal mydriasis did not differ significantly between the two methods. None of the parameters describing the systemic absorption of the drug differed between the treatment groups. Conventionally applied drops caused slightly longer subjective discomfort. Instilling eyedrops on the inner canthus with eyes closed is an alternative method to deliver ocular cyclopentolate with similar efficacy and safety as the conventional technique. This method could be useful especially when treating non-cooperative children.
The oxidation of timolol exhibits genetic polymorphism of debrisoquine type. After oral administration, poor metabolizers have high timolol concentrations in plasma and show an intensified systemic /3-blockade. Since the contribution of debrisoquine metabolizer status on timolol eyedrop therapy is not known we determined the systemic absorption of ocularly applied timolol in healthy subjects classified either extensive or poor metabolizers. Unlike after oral timolol ocular drug administration caused higher peak drug concentrations in plasma in extensive metabolizers. The variation in the systemic absorption of ocular timolol contributed more than the debrisoquine oxidation phenotype to timolol plasma levels after a single ocular timolol application.
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