Allergan has reported better than expected quarterly revenues, helped by strong performance in its US brands segment.

The company said it continues to expect its takeover by Pfizer to close in the second half of this year.

Allergan said revenue in its US brands business rose 38% to about $2.5 billion in the quarter ended December 31, accounting for 58.7% of total revenue. 

Botox global sales were about $460m, while Restasis global sales came in at about $348.2m. 

Pfizer agreed in November to buy Allergan in a $160 billion deal which is meant to slash Pfizer's tax rate as it would shift its headquarters to Dublin. 

The deal has been under intense regulatory scrutiny with US politicians condemning it as a tax-dodge. 

Talking about the speculation around the takeover, CEO Brenton Saunders said he saw no obstacles with the closing of the deal. 

"The deal was constructed in a highly legal way with advice of many experts and I think we're in a very strong position to close this deal in the second half of the year,"  he said. 

Allergan forecast 2016 adjusted revenue of about $17 billion, just shy of the analysts' average estimate of $17.66 billion. 

This estimate takes into account foreign exchange impact of $200m and a $500m decline in the company's low-margin generics business. 

Allergan's net loss narrowed to $700.5m, or $1.78 per share, in the fourth quarter, from $732.9m, or $3.34 per share, a year earlier. 

Excluding special items, Allergan earned $3.41 per share, while analysts were expecting a profit of $3.34 per share, according to Thomson Reuters.

Revenue rose about 74% to $4.20 billion in the quarter, beating analysts' average estimate of $4.19 billion.