Duel-Acting Subcutaneous Microemulsion Formulation for Improved Migraine Treatment with Zolmitriptan and Diclofenac: Formulation and In Vitro-In Vivo Characterization

Subcutaneous triptan provides immediate analgesia in migraine and cluster headache but is limited by high pain recurrence due to rapid drug elimination. A dual-acting subcutaneous formulation providing immediate release of a triptan and slow but sustained release of a nonsteroidal anti-inflammatory drug may provide a longer duration of relief. A microemulsion-based technology has various advantages over other technically complex dosage forms. Oil-in-water microemulsions of zolmitriptan and diclofenac acid using Labrafac Lipophile, Tween 80, Capryol 90 and water were prepared. One formulation was characterised in vitro and found to have uniformly dispersed nanosized globules. The formulation provided differential release of zolmitriptan and diclofenac acid both in vitro as well as in vivo that may be potentially beneficial to migraine patients.     

Testosterone and oxandrolone, a nonaromatizable androgen, specifically amplify the mass and rate of growth hormone (GH) secreted per burst without altering GH secretory burst duration or frequency or the GH half-life

We investigated the mechanisms by which androgens increase mean circulating GH concentrations in boys. We tested two hypotheses: 1) testosterone increases serum GH concentrations at least in part via an androgen receptor-mediated mechanism, rather than exclusively by way of aromatization to estrogen; 2) androgen augments one or more specific features to GH secretion (secretory burst number, amplitude, and/or duration) and/or prolongs the half-life of GH removal. To examine these hypotheses, prepubertal boys with constitutionally delayed development and/or growth were given injections of testosterone (100 mg monthly; n = 7) or treated with oral oxandrolone, a nonaromatizable androgen (1.25 mg twice daily; n = 5). Pulsatile GH release was studied before and during androgen administration by sampling blood at 20-min intervals for 24 h. The immunoreactive GH time series were subjected to a novel deconvolution technique, which revealed that 1) testosterone and oxandrolone each increased mean (24-h) serum GH concentrations significantly; 2) both androgens augmented the daily endogenous GH secretory rate significantly; 3) increased GH production resulted from a higher mass of GH secreted per burst and a higher maximal rate of GH secretion within each burst; and 4) androgens amplified the magnitude of the nyctohemeral rhythm in the mass (but not frequency) of GH secretory pulses. The observed effects of androgen were specific, since the number and duration of GH secretory bursts and the subject-specific GH half-life were unaltered by androgen treatment. We conclude that androgen acting apart from conversion to estrogen is capable of specifically activating the somatotropic axis via distinct neuroendocrine secretory mechanisms.     

Rapid assessment of glycoprotein IIb/IIIa blockade with the platelet function analyzer (PFA-100) during percutaneous coronary intervention

BACKGROUND: The platelet function analyzer PFA-100 (Dade Behring, Miami, Fla) evaluates platelet function by determining the time to occlusion of an aperture in a membrane coated with collagen and adenosine diphosphate or epinephrine as whole blood flows under shear stress conditions. Platelet aggregation causes aperture occlusion, and results are reported as closure time (CT). Interindividual variability is observed in the level of platelet inhibition achieved with use of the current abciximab dosing regimen (0.25-mg/kg bolus + 10-microg/min infusion for 12 hours). The relationships between specific levels of platelet inhibition and clinical efficacy and safety have not been fully established. METHODS AND RESULTS: We prospectively studied platelet function in 27 patients receiving abciximab during percutaneous coronary intervention. This evaluation included determinations of platelet-rich plasma aggregometry, receptor occupancy studies (D3 assay), and CT measurements at baseline and 10 minutes, 4 hours, 12 hours, and 24 hours after the bolus. All patients received abciximab, aspirin, and heparin; patients undergoing coronary stent implantation received aspirin and ticlopidine after the procedure. CT results were reported within 10 minutes after initiation of testing. For 96% of patients, CT was 300 seconds (maximum CT) immediately after abciximab bolus and remained so throughout the infusion. At 24 hours we observed variable recovery from platelet inhibition and in 72% of patients CT returned to normal (< or =130 seconds). CONCLUSIONS: Findings with the PFA-100 were similar to results observed with platelet aggregometry and receptor occupancy measurements. Most patients treated with abciximab exhibit normalized platelet function at 24 hours despite moderate levels of receptor occupancy, suggesting dissociation between occupancy and function.     

A Recombinant Inbred Strain Analysis of Sleep-Time Responses to Several Sedative-Hypnotics

The results of previous studies suggested that the sleep-time differential between long-sleep (LS) and short-sleep (SS) mice decreases for a series of sedative-hypnotic drugs as lipid solubility increases. Using the LS x SS recombinant inbred (RI) strains, we have tested whether this relationship arises because of common genetic influences on the sleep-time responses or was simply a fortuitous difference between LS and SS mice. Mice were sleep-time tested after intraperitoneal injections of a variety of sedative-hypnotic drugs that vary in lipid solubility including alcohols, barbiturates, chloral hydrate, and urethane. Sleep-time values from each of these drugs were compared with ethanol-induced sleep times in the LS x SS RI strains. Significant genetic correlations were observed between ethanol-induced sleep time and those responses elicited by butanol, propanol, and chloral hydrate, but not by pentobarbital or secobarbital. When the partition coefficient (log P) values were compared with the genetic correlations, a significant relationship (r = -0.85) was observed. These data suggest that common genes mediate sedative-hypnotic reactions to ethanol and some drugs resembling it in log P value, and that anesthetic agents with low lipid solubility may be working through different mechanisms than drugs with greater lipid solubilities.     

Human platelet activating antibodies.

Platelet antibodies identified in the plasma of three multiply transfused patients and a woman who had delivered a baby with neonatal alloimmune thrombocytopenia were investigated for their platelet activating properties. Three patients possessed multispecific HLA antibodies reactive with 90 to 100% of the cells on a lymphocytotoxic panel. These antibodies were also detected using the MAIPA assay and MAb w6/32, which recognizes an epitope common to all HLA class I molecules. In addition to HLA antibodies, three of the patients possessed platelet-specific antibodies that were identified by the MAIPA assay as anti-HPA-1a and anti-HPA-3a (one patient) and anti-HPA-1b (two patients). Each of the HLA antibodies when reacted with platelets expressing the corresponding HLA antigens, potently induced aggregation and release of ATP from dense granules. In contrast, the HPA-1b antibodies induced platelet agglutination, but failed to trigger ATP release. However, platelets coated with these latter antibodies were now refractory to subsequent stimulation by ADP. Similarly, when HLA antibodies were reacted with platelets to produce suboptimal activation, the platelets could now be stimulated only poorly or not at all by either epinephrine or thrombin. This was also true for anti-HPA-1b, which, although not inducing aggregation or ATP release by itself, was capable of almost completely blocking thrombin-induced platelet activation. The thrombin-inhibiting activity of these antibodies could partially be reversed by pretreating antibody-coated platelets with epinephrine immediately followed by stimulation with thrombin. These findings suggest that transfused platelets may either be activated or inhibited by reaction with various platelet antibodies. Therefore it is conceivable that the presence of platelet reactive antibodies in multiply transfused recipients may contribute to the increased thrombotic and hemorrhagic symptoms often observed among these patients.     

Do radionuclide and echocardiographic techniques give a universal cut off value for left ventricular ejection fraction that can be used to select patients for treatment with ACE inhibitors after myocardial infarction?

OBJECTIVE--To determine whether echocardiography and radionuclide angiography give comparable results when the left ventricular ejection fraction is measured early after myocardial infarction and thus whether, irrespective of the method used, a single value for the ejection fraction could be used as a guide for starting treatment with an angiotensin converting enzyme inhibitor. DESIGN--Prospective comparison of measurement of left ventricular ejection fraction by echocardiography and radionuclide angiography. SETTING--Coronary care units of two university teaching hospitals in Glasgow. PATIENTS--99 patients studied within 36 hours of acute myocardial infarction. OUTCOME MEASURES--Left ventricular ejection fraction assessed by echocardiography and radionuclide angiography. RESULTS--70 (77%) of the 99 patients had ejection fraction measured by both echocardiographic and radionuclide techniques, 30 in centre 1 and 40 in centre 2. In centre 1 the mean difference (SD) in ejection fraction (radionuclide angiography--echocardiography) was -8 (10%); 95% CI -12 to -4%. In centre 2 the mean difference was -14 (11%); 95% CI -17 to -11%. If patients had been treated with an ACE inhibitor on the basis of a radionuclide ejection fraction of < 40% then 93% in centre 1 (28 of 30) and 98% in centre 2 (39 of 40) would have been treated. This compares with 63% (19 of 30) and 50% (20 of 40), respectively if echocardiography had been used as a guide. CONCLUSION--Measurement of ejection fraction is highly dependent on the method used and it is therefore impossible to quote a universally applicable figure for left ventricular ejection fraction below which an ACE inhibitor should be used after myocardial infarction.     

Antibodies to glutamic acid decarboxylase and peripheral nerve function in type 1 diabetes

Autoimmune mechanisms have been implicated in the pathophysiology of diabetic neuropathy. We studied the association between glutamic acid decarboxylase (GAD65) and islet cell (IA-2) autoantibodies as well as autoantibodies to the autonomic nervous system and peripheral nerve function in recent onset type 1 diabetes. Thirty-seven patients (27 females and 10 males) enrolled 2-22 months after diagnosis. Humoral factors, glycemic control, and peripheral nerve function were measured annually for 3 yr. Patients with high GAD65Ab had worse glycemic control and higher insulin requirements. Patients with high GAD65Ab had slower motor nerve conduction velocities in the median, ulnar, and peroneal nerves (P < 0.025 for each nerve). The mean motor nerve conduction velocity Z scores at the time of the third evaluation was 0.341 +/- 0.25 for the low GAD65Ab patients and -0.600 +/- 0.25 for the high GAD65Ab patients (P < 0.01). Similar differences between the low and high GAD65Ab groups were observed for F wave latencies, thermal threshold detection, and cardiovascular autonomic function. The composite peripheral nerve function Z scores in the low GAD65Ab patients were 0.62 +/- 11, 0.71 +/- 0.19, and 0.21 +/- 0.14 at the first, second, and third evaluations, significantly different from those in the high GAD65Ab patients in whom they were -0.35 +/- 0.15, -0.46 +/- 0.18, and -0.42 +/- 0.16 (P < 0.001). In summary, GAD65Ab in patients with recent onset type 1 diabetes are associated with worse glycemic control and slightly worse peripheral nerve function. Although the latter remained within normal limits and none of the patients had clinical neuropathy, the GAD65Ab-related differences in composite peripheral nerve function were highly significant (P < 0.001) and could not be attributed to GAD65Ab-related differences in glycemic control.