Emergency contraception may avoid pregnancy after unprotected intercourse or when regular contraceptive measures fail. Levonorgestrel, a synthetic gestagen, is recommended for emergency contraception as a single 1.5-mg dose or, alternatively, two 0.75-mg doses taken 12 h apart. Its efficacy is moderate, preventing about 80% of pregnancies. Efficacy is higher the earlier after unprotected intercourse the drug is taken, but it may be administered up to 5 days post-coitum. Tolerance is similar to, or better than, those of other oral emergency contraceptives. Adverse effects include nausea, vomiting, headache, breast tenderness and transient alteration of menstrual bleeding pattern. It is not known whether levonogestrel increases the risk of ectopic pregnancy when the treatment fails. Its use as an ongoing contraceptive method is discouraged. When given before the preovulatory LH peak, levonorgestrel blocks or delays ovulation. It may also affect sperm migration in the female reproductive tract and have an effect on fertilization. Although it has been often postulated, there is no evidence for an anti-implantatory effect. Acquaintance with the method is quite variable among different societies, but it remains underutilized even where it is well known. Advance provision of the drug has been proposed as a way to promote its use. In clinical trials, advance provision did not adversely modify sexual or regular contraceptive behavior, but it did not reduce pregnancy or abortion rate either. Therefore, emergency contraception with levonorgestrel should be regarded as a backup method which is not a substitute for the continued use of more effective contraceptive methods.

La contracepción de emergencia puede evitar el embarazo luego de un coito sin medidas contraceptivas o cuando éstas fallan. Se recomienda el levonorgestrel, un gestágeno sintético, en dosis única de 1.5 mg (alternativamente en dos dosis de 0.75 mg espaciadas 12 h). Su eficacia es moderada, pues impide aproximadamente 80% de los embarazos. La eficacia es mayor cuanto más precozmente se administre, pero puede darse hasta 5 días post-coito. La tolerancia es similar o superior a la de otros preparados empleados con igual propósito. Los efectos adversos comprenden náuseas, vómitos, cefalea, tensión mamaria y alteraciones transitorias en la siguiente menstruación. Se desconoce si el levonorgestrel aumenta la probabilidad de embarazo ectópico cuando el tratamiento fracasa. No se recomienda su empleo como contraceptivo habitual. Cuando se administra antes del pico preovulatorio de LH, el levonorgestrel generalmente bloquea o retrasa la ovulación. Puede asimismo afectar la migración de los espermatozoides en el tracto genital femenino e, indirectamente, la fertilización. Pese a haberse postulado reiteradamente, no existe evidencia de un efecto antiimplantatorio. El conocimiento del método es muy variable en diferentes sociedades, pero aun donde es bien conocido permanece subutilizado. Se ha propuesto proveer levonorgestrel por adelantado para promover su uso. En ensayos clínicos, tal provisión no afectó adversamente el comportamiento sexual ni el empleo de otros contraceptivos, pero tampoco redujo el número de embarazos o abortos. En consecuencia, el empleo de levonorgestrel debe considerarse un método de respaldo que no reemplaza el uso de contraceptivos más eficaces.

Electrophysiological events occur early after fertilization, along with changes in intracellular Ca2+ concentration . Passive electrical parameters were determined in golden hamster oocytes by whole cell patch-clamp method. In separate experiments the effect of 4-aminopyridine on resting oocytes was tested. The single-channel patch clamp configuration was employed to assess the electrical response to fertilization with homologous sperm. Structure of oocytes submitted to patch clamp was evaluated with scanning electron microscopy and found to be preserved. Oocyte diameter was 70.2 ±  2.2 µm; their resting parameters were: membrane potential 23.8 ±  0.8 mV; total membrane specific resistance 519.1 ±  94.6 Ω.cm², and specific capacity 0.99 ±  0.03 µF.cm-2. Total membrane current was decreased by 42 % by 4-aminopyridine. Control oocytes and oocytes exposed to sperm differed in their membrane currents in response to a voltage ramp clamping membrane potential from - 100 mV to + 100 mV. In both cases, currents were largest at the most negative potentials, but sperm-exposed oocytes had larger currents. Additionally, while in control oocytes the current was inward at negative potentials but outward at positive potentials, in the presence of spermatozoa oocytes was inward within the whole voltage range tested. This latter current may represent Ca2+ entry.

Inhaled glucocorticoids (IGs) are today the first-line treatment for bronchial asthma. The systemic effects of inhaled glucocorticoids, such as suppressing the hypothalamic-pituitary-adrenal axis, are generally less than those with oral glucocorticoids. However, there is a long-term risk of adverse effects on bone. The objective of this piece was to review the published data on the effects of IGs on bone metabolism markers and bone mineral density in adults and in pediatric patients. The reviewed studies do not provide uniform results. Nevertheless, in general they suggest that IGs can affect metabolism and bone mineral density, especially: 1) when high doses are administered (more than 400 µg/day in children and more than 800 µg/day in adults), 2) in pediatric patients, in whom growth in stature can also be affected, 3) in patients whose intake of calcium and vitamin D is inadequate, and 4) in postmenopausal women not undergoing hormone replacement therapy. In general, at therapeutically equivalent doses, beclomethasone has a greater deleterious effect on bone than does budesonide, which in turn has more of an effect than does fluticasone. In addition to the obvious precaution of using the lowest effective dose, other proposed preventive measures include: 1) adequate instruction on the use of aerosols, 2) the use of large volume spacer devices, 3) rinsing the mouth after administering IGs, and 4) dietary adjustments or supplements in order to ensure an adequate intake of calcium and vitamin D.

Los glucocorticoides inhalados (GCI) constituyen hoy un tratamiento de primera línea del asma bronquial. Los efectos sistémicos de los GCI, como la supresión del eje hipotalámico- hipofisario-adrenal, son en general menores que los de los glucocorticoides orales. Sin embargo, existe el riesgo de efectos adversos sobre el hueso a largo plazo. El objetivo del presente trabajo fue revisar los datos publicados acerca de los efectos de los GCI sobre los marcadores del metabolismo óseo y la densidad mineral ósea en adultos y en pacientes pediátricos. Aunque los estudios examinados no proporcionan resultados uniformes, en términos generales sugieren que los GCI pueden afectar al metabolismo y a la densidad mineral ósea, en particular 1) cuando se administran a dosis elevadas (más de 400 µg/día en niños y más de 800 µg/día en adultos); 2) en pacientes pediátricos, en los que también pueden afectar al crecimiento en estatura; 3) en pacientes cuya ingesta de calcio y vitamina D es inadecuada, y 4) en mujeres postmenopáusicas sin terapia de reposición hormonal. En general, a dosis terapéuticamente equivalentes, la beclometasona tiene mayor efecto deletéreo sobre el hueso que la budesonida, y esta mayor que la fluticasona. Además de la precaución obvia de utilizar la menor dosis eficaz, se proponen como medidas preventivas: 1) la adecuada instrucción sobre el uso de los aerosoles; 2) el uso de cámaras de inhalación; 3) el enjuague bucal tras la administración de GCI, y 4) ajustes o suplementos dietéticos para asegurar una adecuada ingesta de calcio y vitamina D.