Meltrex ritonavir
New Meltrex tablet (non-refrigerated)
Old (original) capsule (requires refrigeration)


  • Ritonavir (tradename Norvir) is a protease inhibitor (PI) that is now only used to boost drug levels of some other PIs. Ritonavir boosting allows you to use a lower dose of the boosted PI, and makes the PI last longer in your body.
  • Lopinavir/r (Kaletra) includes ritonavir as part of the same tablet. A separate dose is not necessary.
  • Standard adult doses: this varies depending on the PI that ritonavir is boosting. This is usually 1 x 100 mg tablet/capsule for most protease inhibitors but 2 x 200 mg with tipranavir.
  • Ritonavir is recommended to be taken with food. This is not to improve absorption but to reduce side effects like nausea.
  • Side effects: nausea, vomiting, changes in lipids (blood fat) which should be routinely monitored.
  • Other notes: The new metrex tablet formulation, available from 2010, does not require refrigeration. Refrigeration of ritonavir capsules was recommended for the original capsule formualtion. This is not necessary if they are used within 2 months and stored below 25° C (77° F).
  • Drug interactions: Ritonavir can increase or reduce the levels of a wide range of other drugs (this is why is works well as a booster for PIs). Drugs with interactions include some oral contraceptives, sildenafil (Viagra), antibiotics, antifungals, some statins, herbal medicines, methadone and recreational drugs (including ecstasy/ ‘E’). Your doctor or pharmacist needs to know about any prescription or non-prescription drugs or alternative treatments that you take if you are using ritonavir.

Further information

The European patient leaflet and detailed Product Information for ritonavir are available in PDF format from this link on the European Medicines Agency (EMA) website.

The Patient Information is a simplified summary: what the drug is, why it is used, results from studies and cautions including side effects.

The Product Information is a detailed technical summary that you can access as a PDF file by clicking the ‘Product Information’ tab. It describes more precisely how the drug works and how it is processed by your body. This includes, for example, reported food interaction studies in terms of calories or fat content. It includes more details of the study results and a full list of side effects and drug interactions.